From dc644a073769dd8949a75691eb4a5bdeb70a7d51 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Mon, 12 Dec 2016 16:44:44 -0800 Subject: [PATCH] mm: add three more cond_resched() in swapoff Add a cond_resched() in the unuse_pmd_range() loop (so as to call it even when pmd none or trans_huge, like zap_pmd_range() does); and in the unuse_mm() loop (since that might skip over many vmas). shmem_unuse() and radix_tree_locate_item() look good enough already. Those were the obvious places, but in fact the stalls came from find_next_to_unuse(), which sometimes scans through many unused entries. Apply scan_swap_map()'s LATENCY_LIMIT of 256 there too; and only go off to test frontswap_map when a used entry is found. Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1612052155140.13021@eggly.anvils Signed-off-by: Hugh Dickins Reported-by: Eric Dumazet Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/swapfile.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/mm/swapfile.c b/mm/swapfile.c index f30438970cd1..1c6e0321205d 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1234,6 +1234,7 @@ static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud, pmd = pmd_offset(pud, addr); do { + cond_resched(); next = pmd_addr_end(addr, end); if (pmd_none_or_trans_huge_or_clear_bad(pmd)) continue; @@ -1313,6 +1314,7 @@ static int unuse_mm(struct mm_struct *mm, for (vma = mm->mmap; vma; vma = vma->vm_next) { if (vma->anon_vma && (ret = unuse_vma(vma, entry, page))) break; + cond_resched(); } up_read(&mm->mmap_sem); return (ret < 0)? ret: 0; @@ -1350,15 +1352,12 @@ static unsigned int find_next_to_unuse(struct swap_info_struct *si, prev = 0; i = 1; } - if (frontswap) { - if (frontswap_test(si, i)) - break; - else - continue; - } count = READ_ONCE(si->swap_map[i]); if (count && swap_count(count) != SWAP_MAP_BAD) - break; + if (!frontswap || frontswap_test(si, i)) + break; + if ((i % LATENCY_LIMIT) == 0) + cond_resched(); } return i; } -- 2.20.1