Commit 101a5001 authored by Paul Jackson's avatar Paul Jackson Committed by Linus Torvalds
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[PATCH] cpuset memory spread slab cache implementation

Provide the slab cache infrastructure to support cpuset memory spreading.

See the previous patches, cpuset_mem_spread, for an explanation of cpuset
memory spreading.

This patch provides a slab cache SLAB_MEM_SPREAD flag.  If set in the
kmem_cache_create() call defining a slab cache, then any task marked with the
process state flag PF_MEMSPREAD will spread memory page allocations for that
cache over all the allowed nodes, instead of preferring the local (faulting)

On systems not configured with CONFIG_NUMA, this results in no change to the
page allocation code path for slab caches.

On systems with cpusets configured in the kernel, but the "memory_spread"
cpuset option not enabled for the current tasks cpuset, this adds a call to a
cpuset routine and failed bit test of the processor state flag PF_SPREAD_SLAB.

For tasks so marked, a second inline test is done for the slab cache flag
SLAB_MEM_SPREAD, and if that is set and if the allocation is not
in_interrupt(), this adds a call to to a cpuset routine that computes which of
the tasks mems_allowed nodes should be preferred for this allocation.

==> This patch adds another hook into the performance critical
    code path to allocating objects from the slab cache, in the
    ____cache_alloc() chunk, below.  The next patch optimizes this
    hook, reducing the impact of the combined mempolicy plus memory
    spreading hooks on this critical code path to a single check
    against the tasks task_struct flags word.

This patch provides the generic slab flags and logic needed to apply memory
spreading to a particular slab.

A subsequent patch will mark a few specific slab caches for this placement

Signed-off-by: default avatarPaul Jackson <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent fffb60f9
......@@ -46,6 +46,7 @@ typedef struct kmem_cache kmem_cache_t;
what is reclaimable later*/
#define SLAB_PANIC 0x00040000UL /* panic if kmem_cache_create() fails */
#define SLAB_DESTROY_BY_RCU 0x00080000UL /* defer freeing pages to RCU */
#define SLAB_MEM_SPREAD 0x00100000UL /* Spread some memory over cpuset */
/* flags passed to a constructor func */
#define SLAB_CTOR_CONSTRUCTOR 0x001UL /* if not set, then deconstructor */
......@@ -94,6 +94,7 @@
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/compiler.h>
#include <linux/cpuset.h>
#include <linux/seq_file.h>
#include <linux/notifier.h>
#include <linux/kallsyms.h>
......@@ -173,12 +174,12 @@
......@@ -2810,6 +2811,14 @@ static inline void *____cache_alloc(struct kmem_cache *cachep, gfp_t flags)
if (unlikely(current->mempolicy && !in_interrupt())) {
int nid = slab_node(current->mempolicy);
if (nid != numa_node_id())
return __cache_alloc_node(cachep, flags, nid);
if (unlikely(cpuset_do_slab_mem_spread() &&
(cachep->flags & SLAB_MEM_SPREAD) &&
!in_interrupt())) {
int nid = cpuset_mem_spread_node();
if (nid != numa_node_id())
return __cache_alloc_node(cachep, flags, nid);
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