The patch titled
Subject: mm, mempolicy: don't check cpuset seqlock where it doesn't matter
has been added to the -mm tree. Its filename is
mm-mempolicy-dont-check-cpuset-seqlock-where-it-doesnt-matter.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-mempolicy-dont-check-cpuset-seqlock-where-it-doesnt-matter.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-mempolicy-dont-check-cpuset-seqlock-where-it-doesnt-matter.patch
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------------------------------------------------------
From: Vlastimil Babka <vbabka@xxxxxxx>
Subject: 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@xxxxxxx
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Anshuman Khandual <khandual@xxxxxxxxxxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Dimitri Sivanich <sivanich@xxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Li Zefan <lizefan@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mempolicy.c | 16 ----------------
1 file changed, 16 deletions(-)
diff -puN mm/mempolicy.c~mm-mempolicy-dont-check-cpuset-seqlock-where-it-doesnt-matter mm/mempolicy.c
--- a/mm/mempolicy.c~mm-mempolicy-dont-check-cpuset-seqlock-where-it-doesnt-matter
+++ a/mm/mempolicy.c
@@ -1898,12 +1898,9 @@ alloc_pages_vma(gfp_t gfp, int order, st
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);
_
Patches currently in -mm which might be from vbabka@xxxxxxx are
mm-page_alloc-fix-more-premature-oom-due-to-race-with-cpuset-update.patch
mm-mempolicy-stop-adjusting-current-il_next-in-mpol_rebind_nodemask.patch
mm-page_alloc-pass-preferred-nid-instead-of-zonelist-to-allocator.patch
mm-mempolicy-simplify-rebinding-mempolicies-when-updating-cpusets.patch
mm-cpuset-always-use-seqlock-when-changing-tasks-nodemask.patch
mm-mempolicy-dont-check-cpuset-seqlock-where-it-doesnt-matter.patch
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