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mm: avoid unconditional one-tick sleep when swapcache_prepare fails

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Commit 13ddaf26be ("mm/swap: fix race when skipping swapcache")
introduced an unconditional one-tick sleep when `swapcache_prepare()`
fails, which has led to reports of UI stuttering on latency-sensitive
Android devices.  To address this, we can use a waitqueue to wake up tasks
that fail `swapcache_prepare()` sooner, instead of always sleeping for a
full tick.  While tasks may occasionally be woken by an unrelated
`do_swap_page()`, this method is preferable to two scenarios: rapid
re-entry into page faults, which can cause livelocks, and multiple
millisecond sleeps, which visibly degrade user experience.

Oven's testing shows that a single waitqueue resolves the UI stuttering
issue.  If a 'thundering herd' problem becomes apparent later, a waitqueue
hash similar to `folio_wait_table[PAGE_WAIT_TABLE_SIZE]` for page bit
locks can be introduced.

[v-songbaohua@oppo.com: wake_up only when swapcache_wq waitqueue is active]
  Link: https://lkml.kernel.org/r/20241008130807.40833-1-21cnbao@gmail.com
Link: https://lkml.kernel.org/r/20240926211936.75373-1-21cnbao@gmail.com
Fixes: 13ddaf26be ("mm/swap: fix race when skipping swapcache")
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Reported-by: Oven Liyang <liyangouwen1@oppo.com>
Tested-by: Oven Liyang <liyangouwen1@oppo.com>
Cc: Kairui Song <kasong@tencent.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Barry Song 2024-09-27 09:19:36 +12:00 committed by Andrew Morton
parent 1834300798
commit 01626a1823
1 changed files with 13 additions and 2 deletions
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15
mm/memory.c
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@ -4187,6 +4187,8 @@ static struct folio *alloc_swap_folio(struct vm_fault *vmf)
} }
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
static DECLARE_WAIT_QUEUE_HEAD(swapcache_wq);
/* /*
* We enter with non-exclusive mmap_lock (to exclude vma changes, * We enter with non-exclusive mmap_lock (to exclude vma changes,
* but allow concurrent faults), and pte mapped but not yet locked. * but allow concurrent faults), and pte mapped but not yet locked.
@ -4199,6 +4201,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
{ {
struct vm_area_struct *vma = vmf->vma; struct vm_area_struct *vma = vmf->vma;
struct folio *swapcache, *folio = NULL; struct folio *swapcache, *folio = NULL;
DECLARE_WAITQUEUE(wait, current);
struct page *page; struct page *page;
struct swap_info_struct *si = NULL; struct swap_info_struct *si = NULL;
rmap_t rmap_flags = RMAP_NONE; rmap_t rmap_flags = RMAP_NONE;
@ -4297,7 +4300,9 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
* Relax a bit to prevent rapid * Relax a bit to prevent rapid
* repeated page faults. * repeated page faults.
*/ */
add_wait_queue(&swapcache_wq, &wait);
schedule_timeout_uninterruptible(1); schedule_timeout_uninterruptible(1);
remove_wait_queue(&swapcache_wq, &wait);
goto out_page; goto out_page;
} }
need_clear_cache = true; need_clear_cache = true;
@ -4604,8 +4609,11 @@ unlock:
pte_unmap_unlock(vmf->pte, vmf->ptl); pte_unmap_unlock(vmf->pte, vmf->ptl);
out: out:
/* Clear the swap cache pin for direct swapin after PTL unlock */ /* Clear the swap cache pin for direct swapin after PTL unlock */
if (need_clear_cache) if (need_clear_cache) {
swapcache_clear(si, entry, nr_pages); swapcache_clear(si, entry, nr_pages);
if (waitqueue_active(&swapcache_wq))
wake_up(&swapcache_wq);
}
if (si) if (si)
put_swap_device(si); put_swap_device(si);
return ret; return ret;
@ -4620,8 +4628,11 @@ out_release:
folio_unlock(swapcache); folio_unlock(swapcache);
folio_put(swapcache); folio_put(swapcache);
} }
if (need_clear_cache) if (need_clear_cache) {
swapcache_clear(si, entry, nr_pages); swapcache_clear(si, entry, nr_pages);
if (waitqueue_active(&swapcache_wq))
wake_up(&swapcache_wq);
}
if (si) if (si)
put_swap_device(si); put_swap_device(si);
return ret; return ret;