From: Yang Shi <yang.shi@linux.alibaba.com>
To: mhocko@suse.com, vbabka@suse.cz, rientjes@google.com,
kirill@shutemov.name, akpm@linux-foundation.org
Cc: yang.shi@linux.alibaba.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: [v2 PATCH] mm: thp: fix false negative of shmem vma's THP eligibility
Date: Wed, 24 Apr 2019 00:43:01 +0800 [thread overview]
Message-ID: <1556037781-57869-1-git-send-email-yang.shi@linux.alibaba.com> (raw)
The commit 7635d9cbe832 ("mm, thp, proc: report THP eligibility for each
vma") introduced THPeligible bit for processes' smaps. But, when checking
the eligibility for shmem vma, __transparent_hugepage_enabled() is
called to override the result from shmem_huge_enabled(). It may result
in the anonymous vma's THP flag override shmem's. For example, running a
simple test which create THP for shmem, but with anonymous THP disabled,
when reading the process's smaps, it may show:
7fc92ec00000-7fc92f000000 rw-s 00000000 00:14 27764 /dev/shm/test
Size: 4096 kB
...
[snip]
...
ShmemPmdMapped: 4096 kB
...
[snip]
...
THPeligible: 0
And, /proc/meminfo does show THP allocated and PMD mapped too:
ShmemHugePages: 4096 kB
ShmemPmdMapped: 4096 kB
This doesn't make too much sense. The anonymous THP flag should not
intervene shmem THP. Calling shmem_huge_enabled() with checking
MMF_DISABLE_THP sounds good enough. And, we could skip stack and
dax vma check since we already checked if the vma is shmem already.
Fixes: 7635d9cbe832 ("mm, thp, proc: report THP eligibility for each vma")
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
---
v2: Check VM_NOHUGEPAGE per Michal Hocko
mm/huge_memory.c | 4 ++--
mm/shmem.c | 3 +++
2 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 165ea46..5881e82 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -67,8 +67,8 @@ bool transparent_hugepage_enabled(struct vm_area_struct *vma)
{
if (vma_is_anonymous(vma))
return __transparent_hugepage_enabled(vma);
- if (vma_is_shmem(vma) && shmem_huge_enabled(vma))
- return __transparent_hugepage_enabled(vma);
+ if (vma_is_shmem(vma))
+ return shmem_huge_enabled(vma);
return false;
}
diff --git a/mm/shmem.c b/mm/shmem.c
index 2275a0f..6f09a31 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -3873,6 +3873,9 @@ bool shmem_huge_enabled(struct vm_area_struct *vma)
loff_t i_size;
pgoff_t off;
+ if ((vma->vm_flags & VM_NOHUGEPAGE) ||
+ test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
+ return false;
if (shmem_huge == SHMEM_HUGE_FORCE)
return true;
if (shmem_huge == SHMEM_HUGE_DENY)
--
1.8.3.1
next reply other threads:[~2019-04-23 16:43 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-23 16:43 Yang Shi [this message]
2019-04-23 17:52 ` [v2 PATCH] mm: thp: fix false negative of shmem vma's THP eligibility Michal Hocko
2019-04-23 18:34 ` Yang Shi
2019-04-24 0:22 ` Yang Shi
2019-04-24 7:58 ` Michal Hocko
2019-04-28 19:13 ` Yang Shi
2019-05-06 23:37 ` Yang Shi
2019-05-07 10:47 ` Michal Hocko
2019-05-07 17:10 ` Yang Shi
2019-06-06 18:59 ` Yang Shi
2019-06-07 10:57 ` Hugh Dickins
2019-06-07 14:25 ` Michal Hocko
2019-06-07 18:51 ` Yang Shi
2019-04-24 13:10 ` Vlastimil Babka
2019-04-24 15:47 ` Yang Shi
2019-04-24 16:17 ` Vlastimil Babka
2019-04-25 16:44 ` Yang Shi
2019-06-08 3:58 ` Hugh Dickins
2019-06-10 17:33 ` Yang Shi
2019-06-12 18:44 ` Hugh Dickins
2019-06-12 19:59 ` Yang Shi
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