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authorDavid Rientjes <rientjes@google.com>2017-09-09 02:13:41 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2017-09-09 04:26:47 +0300
commit14038302944a1ceda62a104c137d24a62604d98e (patch)
tree94ad493be1d804f812c5fb0729de9afcb8c1d7a5 /fs/proc/task_mmu.c
parent855d97657d4d335970622f0d95ca4966d3f77ee7 (diff)
downloadlinux-14038302944a1ceda62a104c137d24a62604d98e.tar.xz
fs, proc: unconditional cond_resched when reading smaps
If there are large numbers of hugepages to iterate while reading /proc/pid/smaps, the page walk never does cond_resched(). On archs without split pmd locks, there can be significant and observable contention on mm->page_table_lock which cause lengthy delays without rescheduling. Always reschedule in smaps_pte_range() if necessary since the pagewalk iteration can be expensive. Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1708211405520.131071@chino.kir.corp.google.com Signed-off-by: David Rientjes <rientjes@google.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/proc/task_mmu.c')
-rw-r--r--fs/proc/task_mmu.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index d671f1e350d8..7b40e11ede9b 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -611,11 +611,11 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
if (pmd_present(*pmd))
smaps_pmd_entry(pmd, addr, walk);
spin_unlock(ptl);
- return 0;
+ goto out;
}
if (pmd_trans_unstable(pmd))
- return 0;
+ goto out;
/*
* The mmap_sem held all the way back in m_start() is what
* keeps khugepaged out of here and from collapsing things
@@ -625,6 +625,7 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
for (; addr != end; pte++, addr += PAGE_SIZE)
smaps_pte_entry(pte, addr, walk);
pte_unmap_unlock(pte - 1, ptl);
+out:
cond_resched();
return 0;
}