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* sched: Move p->nr_cpus_allowed check to select_task_rq()Wanpeng Li2014-11-161-3/+0
| | | | | | | | | | | | | | Move the p->nr_cpus_allowed check into kernel/sched/core.c: select_task_rq(). This change will make fair.c, rt.c, and deadline.c all start with the same logic. Suggested-and-Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: "pang.xunlei" <pang.xunlei@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1415150077-59053-1-git-send-email-wanpeng.li@linux.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* Merge branch 'sched/urgent' into sched/core, to pick up fixes before ↵Ingo Molnar2014-11-161-0/+2
|\ | | | | | | | | | | applying more changes Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * sched/cputime: Fix clock_nanosleep()/clock_gettime() inconsistencyStanislaw Gruszka2014-11-161-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit d670ec13178d0 "posix-cpu-timers: Cure SMP wobbles" fixes one glibc test case in cost of breaking another one. After that commit, calling clock_nanosleep(TIMER_ABSTIME, X) and then clock_gettime(&Y) can result of Y time being smaller than X time. Reproducer/tester can be found further below, it can be compiled and ran by: gcc -o tst-cpuclock2 tst-cpuclock2.c -pthread while ./tst-cpuclock2 ; do : ; done This reproducer, when running on a buggy kernel, will complain about "clock_gettime difference too small". Issue happens because on start in thread_group_cputimer() we initialize sum_exec_runtime of cputimer with threads runtime not yet accounted and then add the threads runtime to running cputimer again on scheduler tick, making it's sum_exec_runtime bigger than actual threads runtime. KOSAKI Motohiro posted a fix for this problem, but that patch was never applied: https://lkml.org/lkml/2013/5/26/191 . This patch takes different approach to cure the problem. It calls update_curr() when cputimer starts, that assure we will have updated stats of running threads and on the next schedule tick we will account only the runtime that elapsed from cputimer start. That also assure we have consistent state between cpu times of individual threads and cpu time of the process consisted by those threads. Full reproducer (tst-cpuclock2.c): #define _GNU_SOURCE #include <unistd.h> #include <sys/syscall.h> #include <stdio.h> #include <time.h> #include <pthread.h> #include <stdint.h> #include <inttypes.h> /* Parameters for the Linux kernel ABI for CPU clocks. */ #define CPUCLOCK_SCHED 2 #define MAKE_PROCESS_CPUCLOCK(pid, clock) \ ((~(clockid_t) (pid) << 3) | (clockid_t) (clock)) static pthread_barrier_t barrier; /* Help advance the clock. */ static void *chew_cpu(void *arg) { pthread_barrier_wait(&barrier); while (1) ; return NULL; } /* Don't use the glibc wrapper. */ static int do_nanosleep(int flags, const struct timespec *req) { clockid_t clock_id = MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED); return syscall(SYS_clock_nanosleep, clock_id, flags, req, NULL); } static int64_t tsdiff(const struct timespec *before, const struct timespec *after) { int64_t before_i = before->tv_sec * 1000000000ULL + before->tv_nsec; int64_t after_i = after->tv_sec * 1000000000ULL + after->tv_nsec; return after_i - before_i; } int main(void) { int result = 0; pthread_t th; pthread_barrier_init(&barrier, NULL, 2); if (pthread_create(&th, NULL, chew_cpu, NULL) != 0) { perror("pthread_create"); return 1; } pthread_barrier_wait(&barrier); /* The test. */ struct timespec before, after, sleeptimeabs; int64_t sleepdiff, diffabs; const struct timespec sleeptime = {.tv_sec = 0,.tv_nsec = 100000000 }; /* The relative nanosleep. Not sure why this is needed, but its presence seems to make it easier to reproduce the problem. */ if (do_nanosleep(0, &sleeptime) != 0) { perror("clock_nanosleep"); return 1; } /* Get the current time. */ if (clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &before) < 0) { perror("clock_gettime[2]"); return 1; } /* Compute the absolute sleep time based on the current time. */ uint64_t nsec = before.tv_nsec + sleeptime.tv_nsec; sleeptimeabs.tv_sec = before.tv_sec + nsec / 1000000000; sleeptimeabs.tv_nsec = nsec % 1000000000; /* Sleep for the computed time. */ if (do_nanosleep(TIMER_ABSTIME, &sleeptimeabs) != 0) { perror("absolute clock_nanosleep"); return 1; } /* Get the time after the sleep. */ if (clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &after) < 0) { perror("clock_gettime[3]"); return 1; } /* The time after sleep should always be equal to or after the absolute sleep time passed to clock_nanosleep. */ sleepdiff = tsdiff(&sleeptimeabs, &after); if (sleepdiff < 0) { printf("absolute clock_nanosleep woke too early: %" PRId64 "\n", sleepdiff); result = 1; printf("Before %llu.%09llu\n", before.tv_sec, before.tv_nsec); printf("After %llu.%09llu\n", after.tv_sec, after.tv_nsec); printf("Sleep %llu.%09llu\n", sleeptimeabs.tv_sec, sleeptimeabs.tv_nsec); } /* The difference between the timestamps taken before and after the clock_nanosleep call should be equal to or more than the duration of the sleep. */ diffabs = tsdiff(&before, &after); if (diffabs < sleeptime.tv_nsec) { printf("clock_gettime difference too small: %" PRId64 "\n", diffabs); result = 1; } pthread_cancel(th); return result; } Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/20141112155843.GA24803@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | sched/rt: Clean up check_preempt_equal_prio()Wanpeng Li2014-11-041-4/+10
|/ | | | | | | | | | | | | | | | | | | This patch checks if current can be pushed/pulled somewhere else in advance to make logic clear, the same behavior as dl class. - If current can't be migrated, useless to reschedule, let's hope task can move out. - If task is migratable, so let's not schedule it and see if it can be pushed or pulled somewhere else. Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Juri Lelli <juri.lelli@arm.com> Cc: Kirill Tkhai <ktkhai@parallels.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1414708776-124078-1-git-send-email-wanpeng.li@linux.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* Merge branch 'for-3.18-consistent-ops' of ↵Linus Torvalds2014-10-151-1/+1
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu Pull percpu consistent-ops changes from Tejun Heo: "Way back, before the current percpu allocator was implemented, static and dynamic percpu memory areas were allocated and handled separately and had their own accessors. The distinction has been gone for many years now; however, the now duplicate two sets of accessors remained with the pointer based ones - this_cpu_*() - evolving various other operations over time. During the process, we also accumulated other inconsistent operations. This pull request contains Christoph's patches to clean up the duplicate accessor situation. __get_cpu_var() uses are replaced with with this_cpu_ptr() and __this_cpu_ptr() with raw_cpu_ptr(). Unfortunately, the former sometimes is tricky thanks to C being a bit messy with the distinction between lvalues and pointers, which led to a rather ugly solution for cpumask_var_t involving the introduction of this_cpu_cpumask_var_ptr(). This converts most of the uses but not all. Christoph will follow up with the remaining conversions in this merge window and hopefully remove the obsolete accessors" * 'for-3.18-consistent-ops' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: (38 commits) irqchip: Properly fetch the per cpu offset percpu: Resolve ambiguities in __get_cpu_var/cpumask_var_t -fix ia64: sn_nodepda cannot be assigned to after this_cpu conversion. Use __this_cpu_write. percpu: Resolve ambiguities in __get_cpu_var/cpumask_var_t Revert "powerpc: Replace __get_cpu_var uses" percpu: Remove __this_cpu_ptr clocksource: Replace __this_cpu_ptr with raw_cpu_ptr sparc: Replace __get_cpu_var uses avr32: Replace __get_cpu_var with __this_cpu_write blackfin: Replace __get_cpu_var uses tile: Use this_cpu_ptr() for hardware counters tile: Replace __get_cpu_var uses powerpc: Replace __get_cpu_var uses alpha: Replace __get_cpu_var ia64: Replace __get_cpu_var uses s390: cio driver &__get_cpu_var replacements s390: Replace __get_cpu_var uses mips: Replace __get_cpu_var uses MIPS: Replace __get_cpu_var uses in FPU emulator. arm: Replace __this_cpu_ptr with raw_cpu_ptr ...
| * percpu: Resolve ambiguities in __get_cpu_var/cpumask_var_tChristoph Lameter2014-08-281-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | __get_cpu_var can paper over differences in the definitions of cpumask_var_t and either use the address of the cpumask variable directly or perform a fetch of the address of the struct cpumask allocated elsewhere. This is important particularly when using per cpu cpumask_var_t declarations because in one case we have an offset into a per cpu area to handle and in the other case we need to fetch a pointer from the offset. This patch introduces a new macro this_cpu_cpumask_var_ptr() that is defined where cpumask_var_t is defined and performs the proper actions. All use cases where __get_cpu_var is used with cpumask_var_t are converted to the use of this_cpu_cpumask_var_ptr(). Signed-off-by: Christoph Lameter <cl@linux.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* | sched/rt: Use resched_curr() in task_tick_rt()Kirill Tkhai2014-09-241-1/+1
| | | | | | | | | | | | | | | | | | | | | | Some time ago PREEMPT_NEED_RESCHED was implemented, so reschedule technics is a little more difficult now. Signed-off-by: Kirill Tkhai <ktkhai@parallels.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/20140922183642.11015.66039.stgit@localhost Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | sched/rt: Remove useless if from cleanup pick_next_task_rt()Kirill Tkhai2014-09-191-2/+1
| | | | | | | | | | | | | | | | | | | | | | _pick_next_task_rt() never returns NULL. Signed-off-by: Kirill Tkhai <ktkhai@parallels.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: http://lkml.kernel.org/r/1410529321.3569.26.camel@tkhai Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | sched: Add wrapper for checking task_struct::on_rqKirill Tkhai2014-08-201-8/+8
|/ | | | | | | | | | | | | | | | | | | | | | | Implement task_on_rq_queued() and use it everywhere instead of on_rq check. No functional changes. The only exception is we do not use the wrapper in check_for_tasks(), because it requires to export task_on_rq_queued() in global header files. Next patch in series would return it back, so we do not twist it from here to there. Signed-off-by: Kirill Tkhai <ktkhai@parallels.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Paul Turner <pjt@google.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Mike Galbraith <umgwanakikbuti@gmail.com> Cc: Kirill Tkhai <tkhai@yandex.ru> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Nicolas Pitre <nicolas.pitre@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1408528052.23412.87.camel@tkhai Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Transform resched_task() into resched_curr()Kirill Tkhai2014-07-161-13/+14
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | We always use resched_task() with rq->curr argument. It's not possible to reschedule any task but rq's current. The patch introduces resched_curr(struct rq *) to replace all of the repeating patterns. The main aim is cleanup, but there is a little size profit too: (before) $ size kernel/sched/built-in.o text data bss dec hex filename 155274 16445 7042 178761 2ba49 kernel/sched/built-in.o $ size vmlinux text data bss dec hex filename 7411490 1178376 991232 9581098 92322a vmlinux (after) $ size kernel/sched/built-in.o text data bss dec hex filename 155130 16445 7042 178617 2b9b9 kernel/sched/built-in.o $ size vmlinux text data bss dec hex filename 7411362 1178376 991232 9580970 9231aa vmlinux I was choosing between resched_curr() and resched_rq(), and the first name looks better for me. A little lie in Documentation/trace/ftrace.txt. I have not actually collected the tracing again. With a hope the patch won't make execution times much worse :) Signed-off-by: Kirill Tkhai <tkhai@yandex.ru> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/20140628200219.1778.18735.stgit@localhost Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/rt: Enqueue just unthrottled rt_rq back on the stack in ↵Kirill Tkhai2014-07-051-0/+3
| | | | | | | | | | | | | | | | | | __disable_runtime() Make rt_rq available for pick_next_task(). Otherwise, their tasks stay prisoned long time till dead cpu becomes alive again. Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Signed-off-by: Kirill Tkhai <ktkhai@parallels.com> CC: Konstantin Khorenko <khorenko@parallels.com> CC: Ben Segall <bsegall@google.com> CC: Paul Turner <pjt@google.com> CC: Mike Galbraith <umgwanakikbuti@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1403684388.3462.43.camel@tkhai Signed-off-by: Ingo Molnar <mingo@kernel.org>
* Merge branch 'sched-core-for-linus' of ↵Linus Torvalds2014-06-121-2/+1
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull more scheduler updates from Ingo Molnar: "Second round of scheduler changes: - try-to-wakeup and IPI reduction speedups, from Andy Lutomirski - continued power scheduling cleanups and refactorings, from Nicolas Pitre - misc fixes and enhancements" * 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: sched/deadline: Delete extraneous extern for to_ratio() sched/idle: Optimize try-to-wake-up IPI sched/idle: Simplify wake_up_idle_cpu() sched/idle: Clear polling before descheduling the idle thread sched, trace: Add a tracepoint for IPI-less remote wakeups cpuidle: Set polling in poll_idle sched: Remove redundant assignment to "rt_rq" in update_curr_rt(...) sched: Rename capacity related flags sched: Final power vs. capacity cleanups sched: Remove remaining dubious usage of "power" sched: Let 'struct sched_group_power' care about CPU capacity sched/fair: Disambiguate existing/remaining "capacity" usage sched/fair: Change "has_capacity" to "has_free_capacity" sched/fair: Remove "power" from 'struct numa_stats' sched: Fix signedness bug in yield_to() sched/fair: Use time_after() in record_wakee() sched/balancing: Reduce the rate of needless idle load balancing sched/fair: Fix unlocked reads of some cfs_b->quota/period
| * sched: Remove redundant assignment to "rt_rq" in update_curr_rt(...)Giedrius Rekasius2014-06-051-2/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Variable "rt_rq" is used only in block "for_each_sched_rt_entity" so the value assigned to it at the beginning of the update_curr_rt(...) gets overwritten without ever being read. Remove redundant assignment and move variable declaration to the block in which it is being used. Signed-off-by: Giedrius Rekasius <giedrius.rekasius@gmail.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: kernel-janitors@vger.kernel.org Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/1401027811-30066-1-git-send-email-giedrius.rekasius@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | printk: Add printk_deferred_onceJohn Stultz2014-06-041-7/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Two of the three prink_deferred uses are really printk_once style uses, so add a printk_deferred_once macro to simplify those call sites. Signed-off-by: John Stultz <john.stultz@linaro.org> Reviewed-by: Steven Rostedt <rostedt@goodmis.org> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Jiri Bohac <jbohac@suse.cz> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | printk: rename printk_sched to printk_deferredJohn Stultz2014-06-041-1/+1
|/ | | | | | | | | | | | | | | | | | After learning we'll need some sort of deferred printk functionality in the timekeeping core, Peter suggested we rename the printk_sched function so it can be reused by needed subsystems. This only changes the function name. No logic changes. Signed-off-by: John Stultz <john.stultz@linaro.org> Reviewed-by: Steven Rostedt <rostedt@goodmis.org> Cc: Jan Kara <jack@suse.cz> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Jiri Bohac <jbohac@suse.cz> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* sched, nohz: Change rq->nr_running to always use wrappersKirill Tkhai2014-05-221-2/+2
| | | | | | | | | | | | | | | | Sometimes ->nr_running may cross 2 but interrupt is not being sent to rq's cpu. In this case we don't reenable the timer. Looks like this may be the reason for rare unexpected effects, if nohz is enabled. Patch replaces all places of direct changing of nr_running and makes add_nr_running() caring about crossing border. Signed-off-by: Kirill Tkhai <tkhai@yandex.ru> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20140508225830.2469.97461.stgit@localhost Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Revert commit 4c6c4e38c4e9 ("sched/core: Fix endless loop in ↵Kirill Tkhai2014-04-181-0/+10
| | | | | | | | | | | | | | | | pick_next_task()") This reverts commit 4c6c4e38c4e9 ("sched/core: Fix endless loop in pick_next_task()"), which is not necessary after ("sched/rt: Substract number of tasks of throttled queues from rq->nr_running"). Signed-off-by: Kirill Tkhai <tkhai@yandex.ru> Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com> [conflict resolution with stop task checking patch] Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1394835307.18748.34.camel@HP-250-G1-Notebook-PC Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/rt: Substract number of tasks of throttled queues from rq->nr_runningKirill Tkhai2014-04-181-12/+61
| | | | | | | | | | | | | | | | Now rq->rt becomes to be able to be in dequeued or enqueued state. We add new member rt_rq->rt_queued, which is used to indicate this. The member is used only for top queue rq->rt_rq. The goal is to fit generic scheme which is used in deadline and fair classes, i.e. throttled rt_rq's rt_nr_running is beeing substracted from rq->nr_running. Signed-off-by: Kirill Tkhai <tkhai@yandex.ru> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1394835300.18748.33.camel@HP-250-G1-Notebook-PC Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/rt: Add accessors rq_of_rt_se()Kirill Tkhai2014-04-181-2/+15
| | | | | | | | | | Two accessors for RT_GROUP_SCHED and !RT_GROUP_SCHED cases. Signed-off-by: Kirill Tkhai <tkhai@yandex.ru> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1394835295.18748.32.camel@HP-250-G1-Notebook-PC Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/rt: Sum number of all children tasks in hierarhy at ->rt_nr_runningKirill Tkhai2014-04-181-2/+13
| | | | | | | | | | | | | | | | | | | | | | {inc,dec}_rt_tasks() used to count entities which are directly queued on the rt_rq. If an entity was not a task (i.e., it is some queue), its children were not counted. There is no problem here, but now we want to count number of all tasks which are actually queued under the rt_rq in all the hierarchy (except throttled rt queues). Empty queues are not able to be queued and all of the places, which use ->rt_nr_running, just compare it with zero, so we do not break anything here. Signed-off-by: Kirill Tkhai <tkhai@yandex.ru> Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1394835289.18748.31.camel@HP-250-G1-Notebook-PC Cc: linux-kernel@vger.kernel.org [ Twiddled the changelog. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/rt: Do not try to push tasks if pinned task switches to RTKirill V Tkhai2014-04-181-2/+2
| | | | | | | | | | | | | Just switched pinned task is not able to be pushed. If the rq had had several RT tasks before they have already been considered as candidates to be pushed (or pulled). Signed-off-by: Kirill V Tkhai <tkhai@yandex.ru> Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20140312061833.3a43aa64@gandalf.local.home Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Check for stop task appearance when balancing happensKirill Tkhai2014-04-171-3/+4
| | | | | | | | | | | We need to do it like we do for the other higher priority classes.. Signed-off-by: Kirill Tkhai <tkhai@yandex.ru> Cc: Michael wang <wangyun@linux.vnet.ibm.com> Cc: Sasha Levin <sasha.levin@oracle.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/336561397137116@web27h.yandex.ru Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/core: Fix endless loop in pick_next_task()Kirill Tkhai2014-03-111-10/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 1) Single cpu machine case. When rq has only RT tasks, but no one of them can be picked because of throttling, we enter in endless loop. pick_next_task_{dl,rt} return NULL. In pick_next_task_fair() we permanently go to retry if (rq->nr_running != rq->cfs.h_nr_running) return RETRY_TASK; (rq->nr_running is not being decremented when rt_rq becomes throttled). No chances to unthrottle any rt_rq or to wake fair here, because of rq is locked permanently and interrupts are disabled. 2) In case of SMP this can cause a hang too. Although we unlock rq in idle_balance(), interrupts are still disabled. The solution is to check for available tasks in DL and RT classes instead of checking for sum. Signed-off-by: Kirill Tkhai <ktkhai@parallels.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1394098321.19290.11.camel@tkhai Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/rt: Fix picking RT and DL tasks from empty queueKirill Tkhai2014-03-111-0/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | The problems: 1) We check for rt_nr_running before call of put_prev_task(). If previous task is RT, its rt_rq may become throttled and dequeued after this call. In case of p is from rt->rq this just causes picking a task from throttled queue, but in case of its rt_rq is child we are guaranteed catch BUG_ON. 2) The same with deadline class. The only difference we operate on only dl_rq. This patch fixes all the above problems and it adds a small skip in the DL update like we've already done for RT class: if (unlikely((s64)delta_exec <= 0)) return; This will optimize sequential update_curr_dl() calls a little. Signed-off-by: Kirill Tkhai <ktkhai@parallels.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Juri Lelli <juri.lelli@gmail.com> Link: http://lkml.kernel.org/r/1393946746.3643.3.camel@tkhai Signed-off-by: Ingo Molnar <mingo@kernel.org>
* Merge branch 'sched/urgent' into sched/coreIngo Molnar2014-03-111-0/+8
|\ | | | | | | | | | | Pick up fixes before queueing up new changes. Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * sched/deadline: Prevent rt_time growth to infinityJuri Lelli2014-02-271-0/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Kirill Tkhai noted: Since deadline tasks share rt bandwidth, we must care about bandwidth timer set. Otherwise rt_time may grow up to infinity in update_curr_dl(), if there are no other available RT tasks on top level bandwidth. RT task were in fact throttled right after they got enqueued, and never executed again (rt_time never again went below rt_runtime). Peter then proposed to accrue DL execution on rt_time only when rt timer is active, and proposed a patch (this patch is a slight modification of that) to implement that behavior. While this solves Kirill problem, it has a drawback. Indeed, Kirill noted again: It looks we may get into a situation, when all CPU time is shared between RT and DL tasks: rt_runtime = n rt_period = 2n | RT working, DL sleeping | DL working, RT sleeping | ----------------------------------------------------------- | (1) duration = n | (2) duration = n | (repeat) |--------------------------|------------------------------| | (rt_bw timer is running) | (rt_bw timer is not running) | No time for fair tasks at all. While this can happen during the first period, if rq is always backlogged, RT tasks won't have the opportunity to execute anymore: rt_time reached rt_runtime during (1), suppose after (2) RT is enqueued back, it gets throttled since rt timer didn't fire, replenishment is from now on eaten up by DL tasks that accrue their execution on rt_time (while rt timer is active - we have an RT task waiting for replenishment). FAIR tasks are not touched after this first period. Ok, this is not ideal, and the situation is even worse! What above (the nice case), practically never happens in reality, where your rt timer is not aligned to tasks periods, tasks are in general not periodic, etc.. Long story short, you always risk to overload your system. This patch is based on Peter's idea, but exploits an additional fact: if you don't have RT tasks enqueued, it makes little sense to continue incrementing rt_time once you reached the upper limit (DL tasks have their own mechanism for throttling). This cures both problems: - no matter how many DL instances in the past, you'll have an rt_time slightly above rt_runtime when an RT task is enqueued, and from that point on (after the first replenishment), the task will normally execute; - you can still eat up all bandwidth during the first period, but not anymore after that, remember that DL execution will increment rt_time till the upper limit is reached. The situation is still not perfect! But, we have a simple solution for now, that limits how much you can jeopardize your system, as we keep working towards the right answer: RT groups scheduled using deadline servers. Reported-by: Kirill Tkhai <tkhai@yandex.ru> Signed-off-by: Juri Lelli <juri.lelli@gmail.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/20140225151515.617714e2f2cd6c558531ba61@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | sched: Guarantee task priority in pick_next_task()Peter Zijlstra2014-02-271-1/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Michael spotted that the idle_balance() push down created a task priority problem. Previously, when we called idle_balance() before pick_next_task() it wasn't a problem when -- because of the rq->lock droppage -- an rt/dl task slipped in. Similarly for pre_schedule(), rt pre-schedule could have a dl task slip in. But by pulling it into the pick_next_task() loop, we'll not try a higher task priority again. Cure this by creating a re-start condition in pick_next_task(); and triggering this from pick_next_task_{rt,fair}(). It also fixes a live-lock where we get stuck in pick_next_task_fair() due to idle_balance() seeing !0 nr_running but there not actually being any fair tasks about. Reported-by: Michael Wang <wangyun@linux.vnet.ibm.com> Fixes: 38033c37faab ("sched: Push down pre_schedule() and idle_balance()") Tested-by: Sasha Levin <sasha.levin@oracle.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Juri Lelli <juri.lelli@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/20140224121218.GR15586@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | sched/rt: Make init_sched_rt_calss() __initLi Zefan2014-02-221-1/+1
| | | | | | | | | | | | | | | | | | | | It's a bootstrap function. Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/52F5CC09.1080502@huawei.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | sched: Remove some #ifdefferyPeter Zijlstra2014-02-211-11/+30
| | | | | | | | | | | | | | | | | | | | | | Remove a few gratuitous #ifdefs in pick_next_task*(). Cc: Ingo Molnar <mingo@kernel.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Juri Lelli <juri.lelli@gmail.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/n/tip-nnzddp5c4fijyzzxxrwlxghf@git.kernel.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* | sched: Fix hotplug task migrationPeter Zijlstra2014-02-211-2/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Dan Carpenter reported: > kernel/sched/rt.c:1347 pick_next_task_rt() warn: variable dereferenced before check 'prev' (see line 1338) > kernel/sched/deadline.c:1011 pick_next_task_dl() warn: variable dereferenced before check 'prev' (see line 1005) Kirill also spotted that migrate_tasks() will have an instant NULL deref because pick_next_task() will immediately deref prev. Instead of fixing all the corner cases because migrate_tasks() can pass in a NULL prev task in the unlikely case of hot-un-plug, provide a fake task such that we can remove all the NULL checks from the far more common paths. A further problem; not previously spotted; is that because we pushed pre_schedule() and idle_balance() into pick_next_task() we now need to avoid those getting called and pulling more tasks on our dying CPU. We avoid pull_{dl,rt}_task() by setting fake_task.prio to MAX_PRIO+1. We also note that since we call pick_next_task() exactly the amount of times we have runnable tasks present, we should never land in idle_balance(). Fixes: 38033c37faab ("sched: Push down pre_schedule() and idle_balance()") Cc: Juri Lelli <juri.lelli@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Steven Rostedt <rostedt@goodmis.org> Reported-by: Kirill Tkhai <tkhai@yandex.ru> Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20140212094930.GB3545@laptop.programming.kicks-ass.net Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* | sched: Push down pre_schedule() and idle_balance()Peter Zijlstra2014-02-111-8/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch both merged idle_balance() and pre_schedule() and pushes both of them into pick_next_task(). Conceptually pre_schedule() and idle_balance() are rather similar, both are used to pull more work onto the current CPU. We cannot however first move idle_balance() into pre_schedule_fair() since there is no guarantee the last runnable task is a fair task, and thus we would miss newidle balances. Similarly, the dl and rt pre_schedule calls must be ran before idle_balance() since their respective tasks have higher priority and it would not do to delay their execution searching for less important tasks first. However, by noticing that pick_next_tasks() already traverses the sched_class hierarchy in the right order, we can get the right behaviour and do away with both calls. We must however change the special case optimization to also require that prev is of sched_class_fair, otherwise we can miss doing a dl or rt pull where we needed one. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/n/tip-a8k6vvaebtn64nie345kx1je@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | sched: Push put_prev_task() into pick_next_task()Peter Zijlstra2014-02-101-11/+16
|/ | | | | | | | | | | In order to avoid having to do put/set on a whole cgroup hierarchy when we context switch, push the put into pick_next_task() so that both operations are in the same function. Further changes then allow us to possibly optimize away redundant work. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1328936700.2476.17.camel@laptop Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/deadline: Add SCHED_DEADLINE SMP-related data structures & logicJuri Lelli2014-01-131-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Introduces data structures relevant for implementing dynamic migration of -deadline tasks and the logic for checking if runqueues are overloaded with -deadline tasks and for choosing where a task should migrate, when it is the case. Adds also dynamic migrations to SCHED_DEADLINE, so that tasks can be moved among CPUs when necessary. It is also possible to bind a task to a (set of) CPU(s), thus restricting its capability of migrating, or forbidding migrations at all. The very same approach used in sched_rt is utilised: - -deadline tasks are kept into CPU-specific runqueues, - -deadline tasks are migrated among runqueues to achieve the following: * on an M-CPU system the M earliest deadline ready tasks are always running; * affinity/cpusets settings of all the -deadline tasks is always respected. Therefore, this very special form of "load balancing" is done with an active method, i.e., the scheduler pushes or pulls tasks between runqueues when they are woken up and/or (de)scheduled. IOW, every time a preemption occurs, the descheduled task might be sent to some other CPU (depending on its deadline) to continue executing (push). On the other hand, every time a CPU becomes idle, it might pull the second earliest deadline ready task from some other CPU. To enforce this, a pull operation is always attempted before taking any scheduling decision (pre_schedule()), as well as a push one after each scheduling decision (post_schedule()). In addition, when a task arrives or wakes up, the best CPU where to resume it is selected taking into account its affinity mask, the system topology, but also its deadline. E.g., from the scheduling point of view, the best CPU where to wake up (and also where to push) a task is the one which is running the task with the latest deadline among the M executing ones. In order to facilitate these decisions, per-runqueue "caching" of the deadlines of the currently running and of the first ready task is used. Queued but not running tasks are also parked in another rb-tree to speed-up pushes. Signed-off-by: Juri Lelli <juri.lelli@gmail.com> Signed-off-by: Dario Faggioli <raistlin@linux.it> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1383831828-15501-5-git-send-email-juri.lelli@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/rt: Fix rq's cpupri leak while enqueue/dequeue child RT entitiesKirill Tkhai2013-12-171-0/+14
| | | | | | | | | | | | | | | | | | | | | | | | This patch touches the RT group scheduling case. Functions inc_rt_prio_smp() and dec_rt_prio_smp() change (global) rq's priority, while rt_rq passed to them may be not the top-level rt_rq. This is wrong, because changing of priority on a child level does not guarantee that the priority is the highest all over the rq. So, this leak makes RT balancing unusable. The short example: the task having the highest priority among all rq's RT tasks (no one other task has the same priority) are waking on a throttle rt_rq. The rq's cpupri is set to the task's priority equivalent, but real rq->rt.highest_prio.curr is less. The patch below fixes the problem. Signed-off-by: Kirill Tkhai <tkhai@yandex.ru> Signed-off-by: Peter Zijlstra <peterz@infradead.org> CC: Steven Rostedt <rostedt@goodmis.org> CC: stable@vger.kernel.org Link: http://lkml.kernel.org/r/49231385567953@web4m.yandex.ru Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/rt: Fix task_tick_rt() commentLi Bin2013-10-261-2/+2
| | | | | | | | | | | | This issue was introduced by 454c79999f7e ("sched/rt: Fix SCHED_RR across cgroups") that missed the word 'not'. Fix it. Signed-off-by: Li Bin <huawei.libin@huawei.com> Cc: <guohanjun@huawei.com> Cc: <xiexiuqi@huawei.com> Cc: <peterz@infradead.org> Link: http://lkml.kernel.org/r/1382357743-54136-1-git-send-email-huawei.libin@huawei.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/rt: Add missing rmb()Peter Zijlstra2013-10-161-1/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | While discussing the proposed SCHED_DEADLINE patches which in parts mimic the existing FIFO code it was noticed that the wmb in rt_set_overloaded() didn't have a matching barrier. The only site using rt_overloaded() to test the rto_count is pull_rt_task() and we should issue a matching rmb before then assuming there's an rto_mask bit set. Without that smp_rmb() in there we could actually miss seeing the rto_mask bit. Also, change to using smp_[wr]mb(), even though this is SMP only code; memory barriers without smp_ always make me think they're against hardware of some sort. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: vincent.guittot@linaro.org Cc: luca.abeni@unitn.it Cc: bruce.ashfield@windriver.com Cc: dhaval.giani@gmail.com Cc: rostedt@goodmis.org Cc: hgu1972@gmail.com Cc: oleg@redhat.com Cc: fweisbec@gmail.com Cc: darren@dvhart.com Cc: johan.eker@ericsson.com Cc: p.faure@akatech.ch Cc: paulmck@linux.vnet.ibm.com Cc: raistlin@linux.it Cc: claudio@evidence.eu.com Cc: insop.song@gmail.com Cc: michael@amarulasolutions.com Cc: liming.wang@windriver.com Cc: fchecconi@gmail.com Cc: jkacur@redhat.com Cc: tommaso.cucinotta@sssup.it Cc: Juri Lelli <juri.lelli@gmail.com> Cc: harald.gustafsson@ericsson.com Cc: nicola.manica@disi.unitn.it Cc: tglx@linutronix.de Link: http://lkml.kernel.org/r/20131015103507.GF10651@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/numa: Introduce migrate_swap()Peter Zijlstra2013-10-091-4/+1
| | | | | | | | | | | | | | | | | | | | | | | Use the new stop_two_cpus() to implement migrate_swap(), a function that flips two tasks between their respective cpus. I'm fairly sure there's a less crude way than employing the stop_two_cpus() method, but everything I tried either got horribly fragile and/or complex. So keep it simple for now. The notable detail is how we 'migrate' tasks that aren't runnable anymore. We'll make it appear like we migrated them before they went to sleep. The sole difference is the previous cpu in the wakeup path, so we override this. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Reviewed-by: Rik van Riel <riel@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Signed-off-by: Mel Gorman <mgorman@suse.de> Link: http://lkml.kernel.org/r/1381141781-10992-39-git-send-email-mgorman@suse.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/rt: Remove redundant nr_cpus_allowed testShawn Bohrer2013-10-061-2/+1
| | | | | | | | | | | | | | | | | | | In 76854c7e8f3f4172fef091e78d88b3b751463ac6 ("sched: Use rt.nr_cpus_allowed to recover select_task_rq() cycles") an optimization was added to select_task_rq_rt() that immediately returns when p->nr_cpus_allowed == 1 at the beginning of the function. This makes the latter p->nr_cpus_allowed > 1 check redundant, which can now be removed. Signed-off-by: Shawn Bohrer <sbohrer@rgmadvisors.com> Reviewed-by: Steven Rostedt <rostedt@goodmis.org> Cc: Mike Galbraith <mgalbraith@suse.de> Cc: tomk@rgmadvisors.com Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1380914693-24634-1-git-send-email-shawn.bohrer@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/rt: Simplify pull_rt_task() logic and remove .leaf_rt_rq_listKirill Tkhai2013-06-191-66/+16
| | | | | | | | | | | | | | | | | | | | | | | [ Peter, this is based off of some of my work, I ran it though a few tests and it passed. I also reviewed it, and added my SOB as I am somewhat a co-author to it. ] Based on the patch by Steven Rostedt from previous year: https://lkml.org/lkml/2012/4/18/517 1)Simplify pull_rt_task() logic: search in pushable tasks of dest runqueue. The only pullable tasks are the tasks which are pushable in their local rq, and no others. 2)Remove .leaf_rt_rq_list member of struct rt_rq and functions connected with it: nobody uses it since now. Signed-off-by: Kirill Tkhai <tkhai@yandex.ru> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/287571370557898@web7d.yandex.ru Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Use an accessor to read the rq clockFrederic Weisbecker2013-05-281-4/+4
| | | | | | | | | | | | | | | | Read the runqueue clock through an accessor. This prepares for adding a debugging infrastructure to detect missing or redundant calls to update_rq_clock() between a scheduler's entry and exit point. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul Turner <pjt@google.com> Cc: Mike Galbraith <efault@gmx.de> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1365724262-20142-6-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Remove redundant update_runtime notifierNeil Zhang2013-05-281-40/+0
| | | | | | | | | | | | | | | migration_call() will do all the things that update_runtime() does. So let's remove it. Furthermore, there is potential risk that the current code will catch BUG_ON at line 689 of rt.c when do cpu hotplug while there are realtime threads running because of enabling runtime twice while the rt_runtime may already changed. Signed-off-by: Neil Zhang <zhangwm@marvell.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1365685499-26515-1-git-send-email-zhangwm@marvell.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Use this_rq() helperNathan Zimmer2013-05-101-1/+1
| | | | | | | | | | | | | | | | It is a few instructions more efficent to and slightly more readable to use this_rq()-> instead of cpu_rq(smp_processor_id())-> . Size comparison of kernel/sched/fair.o: text data bss dec hex filename 27972 122 26 28120 6dd8 fair.o.before 27956 122 26 28104 6dc8 fair.o.after Signed-off-by: Nathan Zimmer <nzimmer@sgi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1368116643-87971-1-git-send-email-nzimmer@sgi.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* Merge branch 'sched-core-for-linus' of ↵Linus Torvalds2013-02-191-9/+17
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull scheduler changes from Ingo Molnar: "Main changes: - scheduler side full-dynticks (user-space execution is undisturbed and receives no timer IRQs) preparation changes that convert the cputime accounting code to be full-dynticks ready, from Frederic Weisbecker. - Initial sched.h split-up changes, by Clark Williams - select_idle_sibling() performance improvement by Mike Galbraith: " 1 tbench pair (worst case) in a 10 core + SMT package: pre 15.22 MB/sec 1 procs post 252.01 MB/sec 1 procs " - sched_rr_get_interval() ABI fix/change. We think this detail is not used by apps (so it's not an ABI in practice), but lets keep it under observation. - misc RT scheduling cleanups, optimizations" * 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits) sched/rt: Add <linux/sched/rt.h> header to <linux/init_task.h> cputime: Remove irqsave from seqlock readers sched, powerpc: Fix sched.h split-up build failure cputime: Restore CPU_ACCOUNTING config defaults for PPC64 sched/rt: Move rt specific bits into new header file sched/rt: Add a tuning knob to allow changing SCHED_RR timeslice sched: Move sched.h sysctl bits into separate header sched: Fix signedness bug in yield_to() sched: Fix select_idle_sibling() bouncing cow syndrome sched/rt: Further simplify pick_rt_task() sched/rt: Do not account zero delta_exec in update_curr_rt() cputime: Safely read cputime of full dynticks CPUs kvm: Prepare to add generic guest entry/exit callbacks cputime: Use accessors to read task cputime stats cputime: Allow dynamic switch between tick/virtual based cputime accounting cputime: Generic on-demand virtual cputime accounting cputime: Move default nsecs_to_cputime() to jiffies based cputime file cputime: Librarize per nsecs resolution cputime definitions cputime: Avoid multiplication overflow on utime scaling context_tracking: Export context state for generic vtime ... Fix up conflict in kernel/context_tracking.c due to comment additions.
| * sched/rt: Add a tuning knob to allow changing SCHED_RR timesliceClark Williams2013-02-071-2/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | Add a /proc/sys/kernel scheduler knob named sched_rr_timeslice_ms that allows global changing of the SCHED_RR timeslice value. User visable value is in milliseconds but is stored as jiffies. Setting to 0 (zero) resets to the default (currently 100ms). Signed-off-by: Clark Williams <williams@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/20130207094704.13751796@riff.lan Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * sched/rt: Further simplify pick_rt_task()Kirill Tkhai2013-02-031-2/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Function next_prio() has been removed and pull_rt_task() is the only user of pick_next_highest_task_rt() at the moment. pull_rt_task is not interested in p->nr_cpus_allowed, its only interest is the fact that cpu is allowed to execute p. If nr_cpus_allowed == 1, cpu != task_cpu(p) and cpu is allowed then it means that task p is in the middle of the migration techniques; the task waits until it is moved by migration thread. So, lets pull it earlier. Signed-off-by: Kirill V Tkhai <tkhai@yandex.ru> Acked-by: Steven Rostedt <rostedt@goodmis.org> Cc: Peter Zijlstra <peterz@infradead.org> CC: linux-rt-users <linux-rt-users@vger.kernel.org> Link: http://lkml.kernel.org/r/70871359644177@web16d.yandex.ru Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * sched/rt: Do not account zero delta_exec in update_curr_rt()Kirill Tkhai2013-01-311-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | There are several places of consecutive calls of dequeue_task_rt() and put_prev_task_rt() in the scheduler. For example, function rt_mutex_setprio() does it. The both calls lead to update_curr_rt(), the second of it receives zeroed delta_exec. The only effective action in this case is call of sched_rt_avg_update(), which can change rq->age_stamp and rq->rt_avg. But it is possible in case of ""floating"" rq->clock. This fact is not reasonable to be accounted. Another actions do nothing. Signed-off-by: Kirill V Tkhai <tkhai@yandex.ru> Acked-by: Steven Rostedt <rostedt@goodmis.org> Cc: Peter Zijlstra <peterz@infradead.org> CC: linux-rt-users <linux-rt-users@vger.kernel.org> Link: http://lkml.kernel.org/r/931541359550236@web1g.yandex.ru Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * sched/rt: Avoid updating RT entry timeout twice within one tick periodYing Xue2013-01-251-1/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The issue below was found in 2.6.34-rt rather than mainline rt kernel, but the issue still exists upstream as well. So please let me describe how it was noticed on 2.6.34-rt: On this version, each softirq has its own thread, it means there is at least one RT FIFO task per cpu. The priority of these tasks is set to 49 by default. If user launches an RT FIFO task with priority lower than 49 of softirq RT tasks, it's possible there are two RT FIFO tasks enqueued one cpu runqueue at one moment. By current strategy of balancing RT tasks, when it comes to RT tasks, we really need to put them off to a CPU that they can run on as soon as possible. Even if it means a bit of cache line flushing, we want RT tasks to be run with the least latency. When the user RT FIFO task which just launched before is running, the sched timer tick of the current cpu happens. In this tick period, the timeout value of the user RT task will be updated once. Subsequently, we try to wake up one softirq RT task on its local cpu. As the priority of current user RT task is lower than the softirq RT task, the current task will be preempted by the higher priority softirq RT task. Before preemption, we check to see if current can readily move to a different cpu. If so, we will reschedule to allow the RT push logic to try to move current somewhere else. Whenever the woken softirq RT task runs, it first tries to migrate the user FIFO RT task over to a cpu that is running a task of lesser priority. If migration is done, it will send a reschedule request to the found cpu by IPI interrupt. Once the target cpu responds the IPI interrupt, it will pick the migrated user RT task to preempt its current task. When the user RT task is running on the new cpu, the sched timer tick of the cpu fires. So it will tick the user RT task again. This also means the RT task timeout value will be updated again. As the migration may be done in one tick period, it means the user RT task timeout value will be updated twice within one tick. If we set a limit on the amount of cpu time for the user RT task by setrlimit(RLIMIT_RTTIME), the SIGXCPU signal should be posted upon reaching the soft limit. But exactly when the SIGXCPU signal should be sent depends on the RT task timeout value. In fact the timeout mechanism of sending the SIGXCPU signal assumes the RT task timeout is increased once every tick. However, currently the timeout value may be added twice per tick. So it results in the SIGXCPU signal being sent earlier than expected. To solve this issue, we prevent the timeout value from increasing twice within one tick time by remembering the jiffies value of last updating the timeout. As long as the RT task's jiffies is different with the global jiffies value, we allow its timeout to be updated. Signed-off-by: Ying Xue <ying.xue@windriver.com> Signed-off-by: Fan Du <fan.du@windriver.com> Reviewed-by: Yong Zhang <yong.zhang0@gmail.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> Cc: <peterz@infradead.org> Link: http://lkml.kernel.org/r/1342508623-2887-1-git-send-email-ying.xue@windriver.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * sched/rt: Add reschedule check to switched_from_rt()Kirill Tkhai2013-01-241-2/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | Reschedule rq->curr if the first RT task has just been pulled to the rq. Signed-off-by: Kirill V Tkhai <tkhai@yandex.ru> Acked-by: Steven Rostedt <rostedt@goodmis.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Tkhai Kirill <tkhai@yandex.ru> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/118761353614535@web28f.yandex.ru Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | sched/rt: Use root_domain of rt_rq not current processorShawn Bohrer2013-01-251-1/+1
|/ | | | | | | | | | | | | | | | | | | | | | | | | | When the system has multiple domains do_sched_rt_period_timer() can run on any CPU and may iterate over all rt_rq in cpu_online_mask. This means when balance_runtime() is run for a given rt_rq that rt_rq may be in a different rd than the current processor. Thus if we use smp_processor_id() to get rd in do_balance_runtime() we may borrow runtime from a rt_rq that is not part of our rd. This changes do_balance_runtime to get the rd from the passed in rt_rq ensuring that we borrow runtime only from the correct rd for the given rt_rq. This fixes a BUG at kernel/sched/rt.c:687! in __disable_runtime when we try reclaim runtime lent to other rt_rq but runtime has been lent to a rt_rq in another rd. Signed-off-by: Shawn Bohrer <sbohrer@rgmadvisors.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Mike Galbraith <bitbucket@online.de> Cc: peterz@infradead.org Cc: <stable@kernel.org> Link: http://lkml.kernel.org/r/1358186131-29494-1-git-send-email-sbohrer@rgmadvisors.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Remove __ARCH_WANT_INTERRUPTS_ON_CTXSWPeter Zijlstra2012-09-131-5/+0
| | | | | | | | | | | | Now that the last architecture to use this has stopped doing so (ARM, thanks Catalin!) we can remove this complexity from the scheduler core. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Link: http://lkml.kernel.org/n/tip-g9p2a1w81xxbrze25v9zpzbf@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
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