diff options
Diffstat (limited to 'Documentation/vm')
| -rw-r--r-- | Documentation/vm/00-INDEX | 16 | ||||
| -rw-r--r-- | Documentation/vm/Makefile | 2 | ||||
| -rw-r--r-- | Documentation/vm/hugepage-mmap.c | 91 | ||||
| -rw-r--r-- | Documentation/vm/hugepage-shm.c | 98 | ||||
| -rw-r--r-- | Documentation/vm/hugetlbpage.txt | 169 | ||||
| -rw-r--r-- | Documentation/vm/map_hugetlb.c | 8 | ||||
| -rw-r--r-- | Documentation/vm/numa | 186 | ||||
| -rw-r--r-- | Documentation/vm/numa_memory_policy.txt | 4 | ||||
| -rw-r--r-- | Documentation/vm/slub.txt | 1 |
9 files changed, 360 insertions, 215 deletions
diff --git a/Documentation/vm/00-INDEX b/Documentation/vm/00-INDEX index e57d6a9dd32b..dca82d7c83d8 100644 --- a/Documentation/vm/00-INDEX +++ b/Documentation/vm/00-INDEX @@ -4,23 +4,35 @@ active_mm.txt - An explanation from Linus about tsk->active_mm vs tsk->mm. balance - various information on memory balancing. +hugepage-mmap.c + - Example app using huge page memory with the mmap system call. +hugepage-shm.c + - Example app using huge page memory with Sys V shared memory system calls. hugetlbpage.txt - a brief summary of hugetlbpage support in the Linux kernel. +hwpoison.txt + - explains what hwpoison is ksm.txt - how to use the Kernel Samepage Merging feature. locking - info on how locking and synchronization is done in the Linux vm code. +map_hugetlb.c + - an example program that uses the MAP_HUGETLB mmap flag. numa - information about NUMA specific code in the Linux vm. numa_memory_policy.txt - documentation of concepts and APIs of the 2.6 memory policy support. overcommit-accounting - description of the Linux kernels overcommit handling modes. +page-types.c + - Tool for querying page flags page_migration - description of page migration in NUMA systems. +pagemap.txt + - pagemap, from the userspace perspective slabinfo.c - source code for a tool to get reports about slabs. slub.txt - a short users guide for SLUB. -map_hugetlb.c - - an example program that uses the MAP_HUGETLB mmap flag. +unevictable-lru.txt + - Unevictable LRU infrastructure diff --git a/Documentation/vm/Makefile b/Documentation/vm/Makefile index 5bd269b3731a..9dcff328b964 100644 --- a/Documentation/vm/Makefile +++ b/Documentation/vm/Makefile @@ -2,7 +2,7 @@ obj- := dummy.o # List of programs to build -hostprogs-y := slabinfo page-types +hostprogs-y := slabinfo page-types hugepage-mmap hugepage-shm map_hugetlb # Tell kbuild to always build the programs always := $(hostprogs-y) diff --git a/Documentation/vm/hugepage-mmap.c b/Documentation/vm/hugepage-mmap.c new file mode 100644 index 000000000000..db0dd9a33d54 --- /dev/null +++ b/Documentation/vm/hugepage-mmap.c @@ -0,0 +1,91 @@ +/* + * hugepage-mmap: + * + * Example of using huge page memory in a user application using the mmap + * system call. Before running this application, make sure that the + * administrator has mounted the hugetlbfs filesystem (on some directory + * like /mnt) using the command mount -t hugetlbfs nodev /mnt. In this + * example, the app is requesting memory of size 256MB that is backed by + * huge pages. + * + * For the ia64 architecture, the Linux kernel reserves Region number 4 for + * huge pages. That means that if one requires a fixed address, a huge page + * aligned address starting with 0x800000... will be required. If a fixed + * address is not required, the kernel will select an address in the proper + * range. + * Other architectures, such as ppc64, i386 or x86_64 are not so constrained. + */ + +#include <stdlib.h> +#include <stdio.h> +#include <unistd.h> +#include <sys/mman.h> +#include <fcntl.h> + +#define FILE_NAME "/mnt/hugepagefile" +#define LENGTH (256UL*1024*1024) +#define PROTECTION (PROT_READ | PROT_WRITE) + +/* Only ia64 requires this */ +#ifdef __ia64__ +#define ADDR (void *)(0x8000000000000000UL) +#define FLAGS (MAP_SHARED | MAP_FIXED) +#else +#define ADDR (void *)(0x0UL) +#define FLAGS (MAP_SHARED) +#endif + +static void check_bytes(char *addr) +{ + printf("First hex is %x\n", *((unsigned int *)addr)); +} + +static void write_bytes(char *addr) +{ + unsigned long i; + + for (i = 0; i < LENGTH; i++) + *(addr + i) = (char)i; +} + +static void read_bytes(char *addr) +{ + unsigned long i; + + check_bytes(addr); + for (i = 0; i < LENGTH; i++) + if (*(addr + i) != (char)i) { + printf("Mismatch at %lu\n", i); + break; + } +} + +int main(void) +{ + void *addr; + int fd; + + fd = open(FILE_NAME, O_CREAT | O_RDWR, 0755); + if (fd < 0) { + perror("Open failed"); + exit(1); + } + + addr = mmap(ADDR, LENGTH, PROTECTION, FLAGS, fd, 0); + if (addr == MAP_FAILED) { + perror("mmap"); + unlink(FILE_NAME); + exit(1); + } + + printf("Returned address is %p\n", addr); + check_bytes(addr); + write_bytes(addr); + read_bytes(addr); + + munmap(addr, LENGTH); + close(fd); + unlink(FILE_NAME); + + return 0; +} diff --git a/Documentation/vm/hugepage-shm.c b/Documentation/vm/hugepage-shm.c new file mode 100644 index 000000000000..07956d8592c9 --- /dev/null +++ b/Documentation/vm/hugepage-shm.c @@ -0,0 +1,98 @@ +/* + * hugepage-shm: + * + * Example of using huge page memory in a user application using Sys V shared + * memory system calls. In this example the app is requesting 256MB of + * memory that is backed by huge pages. The application uses the flag + * SHM_HUGETLB in the shmget system call to inform the kernel that it is + * requesting huge pages. + * + * For the ia64 architecture, the Linux kernel reserves Region number 4 for + * huge pages. That means that if one requires a fixed address, a huge page + * aligned address starting with 0x800000... will be required. If a fixed + * address is not required, the kernel will select an address in the proper + * range. + * Other architectures, such as ppc64, i386 or x86_64 are not so constrained. + * + * Note: The default shared memory limit is quite low on many kernels, + * you may need to increase it via: + * + * echo 268435456 > /proc/sys/kernel/shmmax + * + * This will increase the maximum size per shared memory segment to 256MB. + * The other limit that you will hit eventually is shmall which is the + * total amount of shared memory in pages. To set it to 16GB on a system + * with a 4kB pagesize do: + * + * echo 4194304 > /proc/sys/kernel/shmall + */ + +#include <stdlib.h> +#include <stdio.h> +#include <sys/types.h> +#include <sys/ipc.h> +#include <sys/shm.h> +#include <sys/mman.h> + +#ifndef SHM_HUGETLB +#define SHM_HUGETLB 04000 +#endif + +#define LENGTH (256UL*1024*1024) + +#define dprintf(x) printf(x) + +/* Only ia64 requires this */ +#ifdef __ia64__ +#define ADDR (void *)(0x8000000000000000UL) +#define SHMAT_FLAGS (SHM_RND) +#else +#define ADDR (void *)(0x0UL) +#define SHMAT_FLAGS (0) +#endif + +int main(void) +{ + int shmid; + unsigned long i; + char *shmaddr; + + if ((shmid = shmget(2, LENGTH, + SHM_HUGETLB | IPC_CREAT | SHM_R | SHM_W)) < 0) { + perror("shmget"); + exit(1); + } + printf("shmid: 0x%x\n", shmid); + + shmaddr = shmat(shmid, ADDR, SHMAT_FLAGS); + if (shmaddr == (char *)-1) { + perror("Shared memory attach failure"); + shmctl(shmid, IPC_RMID, NULL); + exit(2); + } + printf("shmaddr: %p\n", shmaddr); + + dprintf("Starting the writes:\n"); + for (i = 0; i < LENGTH; i++) { + shmaddr[i] = (char)(i); + if (!(i % (1024 * 1024))) + dprintf("."); + } + dprintf("\n"); + + dprintf("Starting the Check..."); + for (i = 0; i < LENGTH; i++) + if (shmaddr[i] != (char)i) + printf("\nIndex %lu mismatched\n", i); + dprintf("Done.\n"); + + if (shmdt((const void *)shmaddr) != 0) { + perror("Detach failure"); + shmctl(shmid, IPC_RMID, NULL); + exit(3); + } + + shmctl(shmid, IPC_RMID, NULL); + + return 0; +} diff --git a/Documentation/vm/hugetlbpage.txt b/Documentation/vm/hugetlbpage.txt index bc31636973e3..457634c1e03e 100644 --- a/Documentation/vm/hugetlbpage.txt +++ b/Documentation/vm/hugetlbpage.txt @@ -299,176 +299,11 @@ map_hugetlb.c. ******************************************************************* /* - * Example of using huge page memory in a user application using Sys V shared - * memory system calls. In this example the app is requesting 256MB of - * memory that is backed by huge pages. The application uses the flag - * SHM_HUGETLB in the shmget system call to inform the kernel that it is - * requesting huge pages. - * - * For the ia64 architecture, the Linux kernel reserves Region number 4 for - * huge pages. That means that if one requires a fixed address, a huge page - * aligned address starting with 0x800000... will be required. If a fixed - * address is not required, the kernel will select an address in the proper - * range. - * Other architectures, such as ppc64, i386 or x86_64 are not so constrained. - * - * Note: The default shared memory limit is quite low on many kernels, - * you may need to increase it via: - * - * echo 268435456 > /proc/sys/kernel/shmmax - * - * This will increase the maximum size per shared memory segment to 256MB. - * The other limit that you will hit eventually is shmall which is the - * total amount of shared memory in pages. To set it to 16GB on a system - * with a 4kB pagesize do: - * - * echo 4194304 > /proc/sys/kernel/shmall + * hugepage-shm: see Documentation/vm/hugepage-shm.c */ -#include <stdlib.h> -#include <stdio.h> -#include <sys/types.h> -#include <sys/ipc.h> -#include <sys/shm.h> -#include <sys/mman.h> - -#ifndef SHM_HUGETLB -#define SHM_HUGETLB 04000 -#endif - -#define LENGTH (256UL*1024*1024) - -#define dprintf(x) printf(x) - -#define ADDR (void *)(0x0UL) /* let kernel choose address */ -#define SHMAT_FLAGS (0) - -int main(void) -{ - int shmid; - unsigned long i; - char *shmaddr; - - if ((shmid = shmget(2, LENGTH, - SHM_HUGETLB | IPC_CREAT | SHM_R | SHM_W)) < 0) { - perror("shmget"); - exit(1); - } - printf("shmid: 0x%x\n", shmid); - - shmaddr = shmat(shmid, ADDR, SHMAT_FLAGS); - if (shmaddr == (char *)-1) { - perror("Shared memory attach failure"); - shmctl(shmid, IPC_RMID, NULL); - exit(2); - } - printf("shmaddr: %p\n", shmaddr); - - dprintf("Starting the writes:\n"); - for (i = 0; i < LENGTH; i++) { - shmaddr[i] = (char)(i); - if (!(i % (1024 * 1024))) - dprintf("."); - } - dprintf("\n"); - - dprintf("Starting the Check..."); - for (i = 0; i < LENGTH; i++) - if (shmaddr[i] != (char)i) - printf("\nIndex %lu mismatched\n", i); - dprintf("Done.\n"); - - if (shmdt((const void *)shmaddr) != 0) { - perror("Detach failure"); - shmctl(shmid, IPC_RMID, NULL); - exit(3); - } - - shmctl(shmid, IPC_RMID, NULL); - - return 0; -} ******************************************************************* /* - * Example of using huge page memory in a user application using the mmap - * system call. Before running this application, make sure that the - * administrator has mounted the hugetlbfs filesystem (on some directory - * like /mnt) using the command mount -t hugetlbfs nodev /mnt. In this - * example, the app is requesting memory of size 256MB that is backed by - * huge pages. - * - * For the ia64 architecture, the Linux kernel reserves Region number 4 for - * huge pages. That means that if one requires a fixed address, a huge page - * aligned address starting with 0x800000... will be required. If a fixed - * address is not required, the kernel will select an address in the proper - * range. - * Other architectures, such as ppc64, i386 or x86_64 are not so constrained. + * hugepage-mmap: see Documentation/vm/hugepage-mmap.c */ -#include <stdlib.h> -#include <stdio.h> -#include <unistd.h> -#include <sys/mman.h> -#include <fcntl.h> - -#define FILE_NAME "/mnt/hugepagefile" -#define LENGTH (256UL*1024*1024) -#define PROTECTION (PROT_READ | PROT_WRITE) - -#define ADDR (void *)(0x0UL) /* let kernel choose address */ -#define FLAGS (MAP_SHARED) - -void check_bytes(char *addr) -{ - printf("First hex is %x\n", *((unsigned int *)addr)); -} - -void write_bytes(char *addr) -{ - unsigned long i; - - for (i = 0; i < LENGTH; i++) - *(addr + i) = (char)i; -} - -void read_bytes(char *addr) -{ - unsigned long i; - - check_bytes(addr); - for (i = 0; i < LENGTH; i++) - if (*(addr + i) != (char)i) { - printf("Mismatch at %lu\n", i); - break; - } -} - -int main(void) -{ - void *addr; - int fd; - - fd = open(FILE_NAME, O_CREAT | O_RDWR, 0755); - if (fd < 0) { - perror("Open failed"); - exit(1); - } - - addr = mmap(ADDR, LENGTH, PROTECTION, FLAGS, fd, 0); - if (addr == MAP_FAILED) { - perror("mmap"); - unlink(FILE_NAME); - exit(1); - } - - printf("Returned address is %p\n", addr); - check_bytes(addr); - write_bytes(addr); - read_bytes(addr); - - munmap(addr, LENGTH); - close(fd); - unlink(FILE_NAME); - - return 0; -} diff --git a/Documentation/vm/map_hugetlb.c b/Documentation/vm/map_hugetlb.c index e2bdae37f499..eda1a6d3578a 100644 --- a/Documentation/vm/map_hugetlb.c +++ b/Documentation/vm/map_hugetlb.c @@ -19,7 +19,7 @@ #define PROTECTION (PROT_READ | PROT_WRITE) #ifndef MAP_HUGETLB -#define MAP_HUGETLB 0x40 +#define MAP_HUGETLB 0x40000 /* arch specific */ #endif /* Only ia64 requires this */ @@ -31,12 +31,12 @@ #define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB) #endif -void check_bytes(char *addr) +static void check_bytes(char *addr) { printf("First hex is %x\n", *((unsigned int *)addr)); } -void write_bytes(char *addr) +static void write_bytes(char *addr) { unsigned long i; @@ -44,7 +44,7 @@ void write_bytes(char *addr) *(addr + i) = (char)i; } -void read_bytes(char *addr) +static void read_bytes(char *addr) { unsigned long i; diff --git a/Documentation/vm/numa b/Documentation/vm/numa index e93ad9425e2a..a200a386429d 100644 --- a/Documentation/vm/numa +++ b/Documentation/vm/numa @@ -1,41 +1,149 @@ Started Nov 1999 by Kanoj Sarcar <kanoj@sgi.com> -The intent of this file is to have an uptodate, running commentary -from different people about NUMA specific code in the Linux vm. - -What is NUMA? It is an architecture where the memory access times -for different regions of memory from a given processor varies -according to the "distance" of the memory region from the processor. -Each region of memory to which access times are the same from any -cpu, is called a node. On such architectures, it is beneficial if -the kernel tries to minimize inter node communications. Schemes -for this range from kernel text and read-only data replication -across nodes, and trying to house all the data structures that -key components of the kernel need on memory on that node. - -Currently, all the numa support is to provide efficient handling -of widely discontiguous physical memory, so architectures which -are not NUMA but can have huge holes in the physical address space -can use the same code. All this code is bracketed by CONFIG_DISCONTIGMEM. - -The initial port includes NUMAizing the bootmem allocator code by -encapsulating all the pieces of information into a bootmem_data_t -structure. Node specific calls have been added to the allocator. -In theory, any platform which uses the bootmem allocator should -be able to put the bootmem and mem_map data structures anywhere -it deems best. - -Each node's page allocation data structures have also been encapsulated -into a pg_data_t. The bootmem_data_t is just one part of this. To -make the code look uniform between NUMA and regular UMA platforms, -UMA platforms have a statically allocated pg_data_t too (contig_page_data). -For the sake of uniformity, the function num_online_nodes() is also defined -for all platforms. As we run benchmarks, we might decide to NUMAize -more variables like low_on_memory, nr_free_pages etc into the pg_data_t. - -The NUMA aware page allocation code currently tries to allocate pages -from different nodes in a round robin manner. This will be changed to -do concentratic circle search, starting from current node, once the -NUMA port achieves more maturity. The call alloc_pages_node has been -added, so that drivers can make the call and not worry about whether -it is running on a NUMA or UMA platform. +What is NUMA? + +This question can be answered from a couple of perspectives: the +hardware view and the Linux software view. + +From the hardware perspective, a NUMA system is a computer platform that +comprises multiple components or assemblies each of which may contain 0 +or more CPUs, local memory, and/or IO buses. For brevity and to +disambiguate the hardware view of these physical components/assemblies +from the software abstraction thereof, we'll call the components/assemblies +'cells' in this document. + +Each of the 'cells' may be viewed as an SMP [symmetric multi-processor] subset +of the system--although some components necessary for a stand-alone SMP system +may not be populated on any given cell. The cells of the NUMA system are +connected together with some sort of system interconnect--e.g., a crossbar or +point-to-point link are common types of NUMA system interconnects. Both of +these types of interconnects can be aggregated to create NUMA platforms with +cells at multiple distances from other cells. + +For Linux, the NUMA platforms of interest are primarily what is known as Cache +Coherent NUMA or ccNUMA systems. With ccNUMA systems, all memory is visible +to and accessible from any CPU attached to any cell and cache coherency +is handled in hardware by the processor caches and/or the system interconnect. + +Memory access time and effective memory bandwidth varies depending on how far +away the cell containing the CPU or IO bus making the memory access is from the +cell containing the target memory. For example, access to memory by CPUs +attached to the same cell will experience faster access times and higher +bandwidths than accesses to memory on other, remote cells. NUMA platforms +can have cells at multiple remote distances from any given cell. + +Platform vendors don't build NUMA systems just to make software developers' +lives interesting. Rather, this architecture is a means to provide scalable +memory bandwidth. However, to achieve scalable memory bandwidth, system and +application software must arrange for a large majority of the memory references +[cache misses] to be to "local" memory--memory on the same cell, if any--or +to the closest cell with memory. + +This leads to the Linux software view of a NUMA system: + +Linux divides the system's hardware resources into multiple software +abstractions called "nodes". Linux maps the nodes onto the physical cells +of the hardware platform, abstracting away some of the details for some +architectures. As with physical cells, software nodes may contain 0 or more +CPUs, memory and/or IO buses. And, again, memory accesses to memory on +"closer" nodes--nodes that map to closer cells--will generally experience +faster access times and higher effective bandwidth than accesses to more +remote cells. + +For some architectures, such as x86, Linux will "hide" any node representing a +physical cell that has no memory attached, and reassign any CPUs attached to +that cell to a node representing a cell that does have memory. Thus, on +these architectures, one cannot assume that all CPUs that Linux associates with +a given node will see the same local memory access times and bandwidth. + +In addition, for some architectures, again x86 is an example, Linux supports +the emulation of additional nodes. For NUMA emulation, linux will carve up +the existing nodes--or the system memory for non-NUMA platforms--into multiple +nodes. Each emulated node will manage a fraction of the underlying cells' +physical memory. NUMA emluation is useful for testing NUMA kernel and +application features on non-NUMA platforms, and as a sort of memory resource +management mechanism when used together with cpusets. +[see Documentation/cgroups/cpusets.txt] + +For each node with memory, Linux constructs an independent memory management +subsystem, complete with its own free page lists, in-use page lists, usage +statistics and locks to mediate access. In addition, Linux constructs for +each memory zone [one or more of DMA, DMA32, NORMAL, HIGH_MEMORY, MOVABLE], +an ordered "zonelist". A zonelist specifies the zones/nodes to visit when a +selected zone/node cannot satisfy the allocation request. This situation, +when a zone has no available memory to satisfy a request, is called +"overflow" or "fallback". + +Because some nodes contain multiple zones containing different types of +memory, Linux must decide whether to order the zonelists such that allocations +fall back to the same zone type on a different node, or to a different zone +type on the same node. This is an important consideration because some zones, +such as DMA or DMA32, represent relatively scarce resources. Linux chooses +a default zonelist order based on the sizes of the various zone types relative +to the total memory of the node and the total memory of the system. The +default zonelist order may be overridden using the numa_zonelist_order kernel +boot parameter or sysctl. [see Documentation/kernel-parameters.txt and +Documentation/sysctl/vm.txt] + +By default, Linux will attempt to satisfy memory allocation requests from the +node to which the CPU that executes the request is assigned. Specifically, +Linux will attempt to allocate from the first node in the appropriate zonelist +for the node where the request originates. This is called "local allocation." +If the "local" node cannot satisfy the request, the kernel will examine other +nodes' zones in the selected zonelist looking for the first zone in the list +that can satisfy the request. + +Local allocation will tend to keep subsequent access to the allocated memory +"local" to the underlying physical resources and off the system interconnect-- +as long as the task on whose behalf the kernel allocated some memory does not +later migrate away from that memory. The Linux scheduler is aware of the +NUMA topology of the platform--embodied in the "scheduling domains" data +structures [see Documentation/scheduler/sched-domains.txt]--and the scheduler +attempts to minimize task migration to distant scheduling domains. However, +the scheduler does not take a task's NUMA footprint into account directly. +Thus, under sufficient imbalance, tasks can migrate between nodes, remote +from their initial node and kernel data structures. + +System administrators and application designers can restrict a task's migration +to improve NUMA locality using various CPU affinity command line interfaces, +such as taskset(1) and numactl(1), and program interfaces such as +sched_setaffinity(2). Further, one can modify the kernel's default local +allocation behavior using Linux NUMA memory policy. +[see Documentation/vm/numa_memory_policy.] + +System administrators can restrict the CPUs and nodes' memories that a non- +privileged user can specify in the scheduling or NUMA commands and functions +using control groups and CPUsets. [see Documentation/cgroups/CPUsets.txt] + +On architectures that do not hide memoryless nodes, Linux will include only +zones [nodes] with memory in the zonelists. This means that for a memoryless +node the "local memory node"--the node of the first zone in CPU's node's +zonelist--will not be the node itself. Rather, it will be the node that the +kernel selected as the nearest node with memory when it built the zonelists. +So, default, local allocations will succeed with the kernel supplying the +closest available memory. This is a consequence of the same mechanism that +allows such allocations to fallback to other nearby nodes when a node that +does contain memory overflows. + +Some kernel allocations do not want or cannot tolerate this allocation fallback +behavior. Rather they want to be sure they get memory from the specified node +or get notified that the node has no free memory. This is usually the case when +a subsystem allocates per CPU memory resources, for example. + +A typical model for making such an allocation is to obtain the node id of the +node to which the "current CPU" is attached using one of the kernel's +numa_node_id() or CPU_to_node() functions and then request memory from only +the node id returned. When such an allocation fails, the requesting subsystem +may revert to its own fallback path. The slab kernel memory allocator is an +example of this. Or, the subsystem may choose to disable or not to enable +itself on allocation failure. The kernel profiling subsystem is an example of +this. + +If the architecture supports--does not hide--memoryless nodes, then CPUs +attached to memoryless nodes would always incur the fallback path overhead +or some subsystems would fail to initialize if they attempted to allocated +memory exclusively from a node without memory. To support such +architectures transparently, kernel subsystems can use the numa_mem_id() +or cpu_to_mem() function to locate the "local memory node" for the calling or +specified CPU. Again, this is the same node from which default, local page +allocations will be attempted. diff --git a/Documentation/vm/numa_memory_policy.txt b/Documentation/vm/numa_memory_policy.txt index be45dbb9d7f2..6690fc34ef6d 100644 --- a/Documentation/vm/numa_memory_policy.txt +++ b/Documentation/vm/numa_memory_policy.txt @@ -45,7 +45,7 @@ most general to most specific: to establish the task policy for a child task exec()'d from an executable image that has no awareness of memory policy. See the MEMORY POLICY APIS section, below, for an overview of the system call - that a task may use to set/change it's task/process policy. + that a task may use to set/change its task/process policy. In a multi-threaded task, task policies apply only to the thread [Linux kernel task] that installs the policy and any threads @@ -301,7 +301,7 @@ decrement this reference count, respectively. mpol_put() will only free the structure back to the mempolicy kmem cache when the reference count goes to zero. -When a new memory policy is allocated, it's reference count is initialized +When a new memory policy is allocated, its reference count is initialized to '1', representing the reference held by the task that is installing the new policy. When a pointer to a memory policy structure is stored in another structure, another reference is added, as the task's reference will be dropped diff --git a/Documentation/vm/slub.txt b/Documentation/vm/slub.txt index b37300edf27c..07375e73981a 100644 --- a/Documentation/vm/slub.txt +++ b/Documentation/vm/slub.txt @@ -41,6 +41,7 @@ Possible debug options are P Poisoning (object and padding) U User tracking (free and alloc) T Trace (please only use on single slabs) + A Toggle failslab filter mark for the cache O Switch debugging off for caches that would have caused higher minimum slab orders - Switch all debugging off (useful if the kernel is |
