The patch titled
Subject: mm/munlock: add lru_add_drain() to fix memcg_stat_test
has been added to the -mm tree. Its filename is
mm-munlock-add-lru_add_drain-to-fix-memcg_stat_test.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-munlock-add-lru_add_drain-to-fix-memcg_stat_test.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-munlock-add-lru_add_drain-to-fix-memcg_stat_test.patch
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------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: mm/munlock: add lru_add_drain() to fix memcg_stat_test
Mike reports that LTP memcg_stat_test usually leads to...
memcg_stat_test 3 TINFO: Test unevictable with MAP_LOCKED
memcg_stat_test 3 TINFO: Running memcg_process --mmap-lock1 -s 135168
memcg_stat_test 3 TINFO: Warming up pid: 3460
memcg_stat_test 3 TINFO: Process is still here after warm up: 3460
memcg_stat_test 3 TFAIL: unevictable is 122880, 135168 expected
...but may lead to...
memcg_stat_test 4 TINFO: Test unevictable with mlock
memcg_stat_test 4 TINFO: Running memcg_process --mmap-lock2 -s 135168
memcg_stat_test 4 TINFO: Warming up pid: 4271
memcg_stat_test 4 TINFO: Process is still here after warm up: 4271
memcg_stat_test 4 TFAIL: unevictable is 122880, 135168 expected
...or both. A wee bit flaky.
follow_page_pte() used to have an lru_add_drain() per each page mlocked,
and the test came to rely on accurate stats. The pagevec to be drained is
different now, but still covered by lru_add_drain(); and, never mind the
test, I believe it's in everyone's interest that a bulk faulting interface
like populate_vma_page_range() or faultin_vma_page_range() should drain
its local pagevecs at the end, to save others sometimes needing the much
more expensive lru_add_drain_all(). This does not absolutely guarantee
exact stats - the mlocking task can be migrated between CPUs as it
proceeds - but it's good enough and the tests pass.
Link: https://lkml.kernel.org/r/47f6d39c-a075-50cb-1cfb-26dd957a48af@xxxxxxxxxx
Fixes: b67bf49ce7aa ("mm/munlock: delete FOLL_MLOCK and FOLL_POPULATE")
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Reported-by: Mike Galbraith <efault@xxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/gup.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
--- a/mm/gup.c~mm-munlock-add-lru_add_drain-to-fix-memcg_stat_test
+++ a/mm/gup.c
@@ -1404,6 +1404,7 @@ long populate_vma_page_range(struct vm_a
struct mm_struct *mm = vma->vm_mm;
unsigned long nr_pages = (end - start) / PAGE_SIZE;
int gup_flags;
+ long ret;
VM_BUG_ON(!PAGE_ALIGNED(start));
VM_BUG_ON(!PAGE_ALIGNED(end));
@@ -1438,8 +1439,10 @@ long populate_vma_page_range(struct vm_a
* We made sure addr is within a VMA, so the following will
* not result in a stack expansion that recurses back here.
*/
- return __get_user_pages(mm, start, nr_pages, gup_flags,
+ ret = __get_user_pages(mm, start, nr_pages, gup_flags,
NULL, NULL, locked);
+ lru_add_drain();
+ return ret;
}
/*
@@ -1471,6 +1474,7 @@ long faultin_vma_page_range(struct vm_ar
struct mm_struct *mm = vma->vm_mm;
unsigned long nr_pages = (end - start) / PAGE_SIZE;
int gup_flags;
+ long ret;
VM_BUG_ON(!PAGE_ALIGNED(start));
VM_BUG_ON(!PAGE_ALIGNED(end));
@@ -1498,8 +1502,10 @@ long faultin_vma_page_range(struct vm_ar
if (check_vma_flags(vma, gup_flags))
return -EINVAL;
- return __get_user_pages(mm, start, nr_pages, gup_flags,
+ ret = __get_user_pages(mm, start, nr_pages, gup_flags,
NULL, NULL, locked);
+ lru_add_drain();
+ return ret;
}
/*
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
mm-munlock-remove-fields-to-fix-htmldocs-warnings.patch
mm-munlock-add-lru_add_drain-to-fix-memcg_stat_test.patch
