The patch titled
Subject: fs, proc: unconditional cond_resched when reading smaps
has been added to the -mm tree. Its filename is
fs-proc-unconditional-cond_resched-when-reading-smaps.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/fs-proc-unconditional-cond_resched-when-reading-smaps.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/fs-proc-unconditional-cond_resched-when-reading-smaps.patch
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------------------------------------------------------
From: David Rientjes <rientjes@xxxxxxxxxx>
Subject: 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@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/task_mmu.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff -puN fs/proc/task_mmu.c~fs-proc-unconditional-cond_resched-when-reading-smaps fs/proc/task_mmu.c
--- a/fs/proc/task_mmu.c~fs-proc-unconditional-cond_resched-when-reading-smaps
+++ a/fs/proc/task_mmu.c
@@ -611,11 +611,11 @@ static int smaps_pte_range(pmd_t *pmd, u
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, u
for (; addr != end; pte++, addr += PAGE_SIZE)
smaps_pte_entry(pte, addr, walk);
pte_unmap_unlock(pte - 1, ptl);
+out:
cond_resched();
return 0;
}
_
Patches currently in -mm which might be from rientjes@xxxxxxxxxx are
mm-oom-let-oom_reap_task-and-exit_mmap-to-run-concurrently-fix-2.patch
mm-compaction-kcompactd-should-not-ignore-pageblock-skip.patch
mm-compaction-persistently-skip-hugetlbfs-pageblocks.patch
mm-compaction-persistently-skip-hugetlbfs-pageblocks-fix.patch
fs-proc-unconditional-cond_resched-when-reading-smaps.patch
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