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mm, mempolicy: don't check cpuset seqlock where it doesn't matter 

Two wrappers of __alloc_pages_nodemask() are checking
task->mems_allowed_seq themselves to retry allocation that has raced
with a cpuset update.

This has been shown to be ineffective in preventing premature OOM's
which can happen in __alloc_pages_slowpath() long before it returns back
to the wrappers to detect the race at that level.

Previous patches have made __alloc_pages_slowpath() more robust, so we
can now simply remove the seqlock checking in the wrappers to prevent
further wrong impression that it can actually help.

Link: http://lkml.kernel.org/r/20170517081140.30654-7-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dimitri Sivanich <sivanich@sgi.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
zero-colors
Vlastimil Babka 2017-07-06 15:40:13 -07:00 committed by Linus Torvalds
parent 5f155f27cb
commit e0dd7d53a6
1 changed files with 0 additions and 16 deletions
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16
mm/mempolicy.c
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@ -1898,12 +1898,9 @@ alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
struct mempolicy *pol;
struct page *page;
int preferred_nid;
unsigned int cpuset_mems_cookie;
nodemask_t *nmask;
retry_cpuset:
pol = get_vma_policy(vma, addr);
cpuset_mems_cookie = read_mems_allowed_begin();
if (pol->mode == MPOL_INTERLEAVE) {
unsigned nid;
@ -1945,8 +1942,6 @@ retry_cpuset:
page = __alloc_pages_nodemask(gfp, order, preferred_nid, nmask);
mpol_cond_put(pol);
out:
if (unlikely(!page && read_mems_allowed_retry(cpuset_mems_cookie)))
goto retry_cpuset;
return page;
}
@ -1964,23 +1959,15 @@ out:
* Allocate a page from the kernel page pool. When not in
* interrupt context and apply the current process NUMA policy.
* Returns NULL when no page can be allocated.
*
* Don't call cpuset_update_task_memory_state() unless
* 1) it's ok to take cpuset_sem (can WAIT), and
* 2) allocating for current task (not interrupt).
*/
struct page *alloc_pages_current(gfp_t gfp, unsigned order)
{
struct mempolicy *pol = &default_policy;
struct page *page;
unsigned int cpuset_mems_cookie;
if (!in_interrupt() && !(gfp & __GFP_THISNODE))
pol = get_task_policy(current);
retry_cpuset:
cpuset_mems_cookie = read_mems_allowed_begin();
/*
* No reference counting needed for current->mempolicy
* nor system default_policy
@ -1992,9 +1979,6 @@ retry_cpuset:
policy_node(gfp, pol, numa_node_id()),
policy_nodemask(gfp, pol));
if (unlikely(!page && read_mems_allowed_retry(cpuset_mems_cookie)))
goto retry_cpuset;
return page;
}
EXPORT_SYMBOL(alloc_pages_current);