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| author | David Rientjes <rientjes@google.com> | 2017-09-08 16:13:41 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-09-08 18:26:47 -0700 |
| commit | 14038302944a1ceda62a104c137d24a62604d98e (patch) | |
| tree | 94ad493be1d804f812c5fb0729de9afcb8c1d7a5 | |
| parent | 855d97657d4d335970622f0d95ca4966d3f77ee7 (diff) | |
| download | linux-14038302944a1ceda62a104c137d24a62604d98e.tar.gz | |
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>
| -rw-r--r-- | fs/proc/task_mmu.c | 5 |
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; } |