diff options
Diffstat (limited to 'init/Kconfig')
| -rw-r--r-- | init/Kconfig | 64 |
1 files changed, 47 insertions, 17 deletions
diff --git a/init/Kconfig b/init/Kconfig index 92a1296ba9fa..a30fe085940e 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -461,6 +461,33 @@ config RCU_FANOUT Select a specific number if testing RCU itself. Take the default if unsure. +config RCU_FANOUT_LEAF + int "Tree-based hierarchical RCU leaf-level fanout value" + range 2 RCU_FANOUT if 64BIT + range 2 RCU_FANOUT if !64BIT + depends on TREE_RCU || TREE_PREEMPT_RCU + default 16 + help + This option controls the leaf-level fanout of hierarchical + implementations of RCU, and allows trading off cache misses + against lock contention. Systems that synchronize their + scheduling-clock interrupts for energy-efficiency reasons will + want the default because the smaller leaf-level fanout keeps + lock contention levels acceptably low. Very large systems + (hundreds or thousands of CPUs) will instead want to set this + value to the maximum value possible in order to reduce the + number of cache misses incurred during RCU's grace-period + initialization. These systems tend to run CPU-bound, and thus + are not helped by synchronized interrupts, and thus tend to + skew them, which reduces lock contention enough that large + leaf-level fanouts work well. + + Select a specific number if testing RCU itself. + + Select the maximum permissible value for large systems. + + Take the default if unsure. + config RCU_FANOUT_EXACT bool "Disable tree-based hierarchical RCU auto-balancing" depends on TREE_RCU || TREE_PREEMPT_RCU @@ -518,10 +545,25 @@ config RCU_BOOST_PRIO depends on RCU_BOOST default 1 help - This option specifies the real-time priority to which preempted - RCU readers are to be boosted. If you are working with CPU-bound - real-time applications, you should specify a priority higher then - the highest-priority CPU-bound application. + This option specifies the real-time priority to which long-term + preempted RCU readers are to be boosted. If you are working + with a real-time application that has one or more CPU-bound + threads running at a real-time priority level, you should set + RCU_BOOST_PRIO to a priority higher then the highest-priority + real-time CPU-bound thread. The default RCU_BOOST_PRIO value + of 1 is appropriate in the common case, which is real-time + applications that do not have any CPU-bound threads. + + Some real-time applications might not have a single real-time + thread that saturates a given CPU, but instead might have + multiple real-time threads that, taken together, fully utilize + that CPU. In this case, you should set RCU_BOOST_PRIO to + a priority higher than the lowest-priority thread that is + conspiring to prevent the CPU from running any non-real-time + tasks. For example, if one thread at priority 10 and another + thread at priority 5 are between themselves fully consuming + the CPU time on a given CPU, then RCU_BOOST_PRIO should be + set to priority 6 or higher. Specify the real-time priority, or take the default if unsure. @@ -1159,7 +1201,7 @@ menu "Kernel Performance Events And Counters" config PERF_EVENTS bool "Kernel performance events and counters" - default y if (PROFILING || PERF_COUNTERS) + default y if PROFILING depends on HAVE_PERF_EVENTS select ANON_INODES select IRQ_WORK @@ -1186,18 +1228,6 @@ config PERF_EVENTS Say Y if unsure. -config PERF_COUNTERS - bool "Kernel performance counters (old config option)" - depends on HAVE_PERF_EVENTS - help - This config has been obsoleted by the PERF_EVENTS - config option - please see that one for details. - - It has no effect on the kernel whether you enable - it or not, it is a compatibility placeholder. - - Say N if unsure. - config DEBUG_PERF_USE_VMALLOC default n bool "Debug: use vmalloc to back perf mmap() buffers" |
