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BACKPORT: mm: avoid unconditional one-tick sleep when swapcache_prepare fails

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Commit 13ddaf26be32 ("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: 13ddaf26be32 ("mm/swap: fix race when skipping swapcache")
Change-Id: I6cd3d6ef318d660ee6290554b5e864d90a70b920
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>
(cherry picked from commit 01626a18230246efdcea322aa8f067e60ffe5ccd)
Bug: 313807618
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
Signed-off-by: Oven <liyangouwen1@oppo.com>
This commit is contained in:
Barry Song
2024-09-27 09:19:36 +12:00
committed by Isaac Manjarres
parent 9e207186c7
commit db710ea87c
1 changed files with 13 additions and 2 deletions
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15
mm/memory.c
View File

@@ -3838,6 +3838,8 @@ static vm_fault_t handle_pte_marker(struct vm_fault *vmf)
return VM_FAULT_SIGBUS;
}
static DECLARE_WAIT_QUEUE_HEAD(swapcache_wq);
/*
* We enter with non-exclusive mmap_lock (to exclude vma changes,
* but allow concurrent faults), and pte mapped but not yet locked.
@@ -3850,6 +3852,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
struct folio *swapcache, *folio = NULL;
DECLARE_WAITQUEUE(wait, current);
struct page *page;
struct swap_info_struct *si = NULL;
rmap_t rmap_flags = RMAP_NONE;
@@ -3933,7 +3936,9 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
*/
if (swapcache_prepare(entry)) {
/* Relax a bit to prevent rapid repeated page faults */
add_wait_queue(&swapcache_wq, &wait);
schedule_timeout_uninterruptible(1);
remove_wait_queue(&swapcache_wq, &wait);
goto out;
}
need_clear_cache = true;
@@ -4189,8 +4194,11 @@ unlock:
pte_unmap_unlock(vmf->pte, vmf->ptl);
out:
/* Clear the swap cache pin for direct swapin after PTL unlock */
if (need_clear_cache)
if (need_clear_cache) {
swapcache_clear(si, entry);
if (waitqueue_active(&swapcache_wq))
wake_up(&swapcache_wq);
}
if (si)
put_swap_device(si);
return ret;
@@ -4204,8 +4212,11 @@ out_release:
folio_unlock(swapcache);
folio_put(swapcache);
}
if (need_clear_cache)
if (need_clear_cache) {
swapcache_clear(si, entry);
if (waitqueue_active(&swapcache_wq))
wake_up(&swapcache_wq);
}
if (si)
put_swap_device(si);
return ret;