From: David Rientjes Date: Fri, 8 Sep 2017 23:13:41 +0000 (-0700) Subject: fs, proc: unconditional cond_resched when reading smaps X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=14038302944a1ceda62a104c137d24a62604d98e;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git 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 Cc: Minchan Kim Cc: Hugh Dickins Cc: "Kirill A. Shutemov" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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; }