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b=pifckaH2MyFug5eITCsVdAEQW7HTOfYaFa55sYQ+RG2VgbNJVnT6tZSxdUhh/Uf5G fr4Tgzia8OwcuiqlXdbo/wuBa/ssTLl/Kpz6qoRjvs+0h6gg5Ib7b96YNwPXzvOiKp hQJxD6FLUGTqzkywv4Nj9aDVmp1/amCSOsC5ZKOAsVQcMovSmQywKnfCvAoQEDaE+K dKsP6LYPHECIiNr/uzMKUiMp+D+JZphCmoaGYeKEZom0LNLDG/+E+hJqVsqHWwCOv/ N0mNwAzY7qKtBHMIAX2J92Pqjx6J1Fk/j1vL0lLfdBHkM3N4pVv4LGfMj2PQ5q7KnL MI39rZZqTO9tw== From: Sasha Levin To: stable@vger.kernel.org, baohua@kernel.org Cc: Barry Song , Oven Liyang , Kairui Song , "Huang, Ying" , Yu Zhao , David Hildenbrand , Chris Li , Hugh Dickins , Johannes Weiner , Matthew Wilcox , Michal Hocko , Minchan Kim , Yosry Ahmed , SeongJae Park , Kalesh Singh , Suren Baghdasaryan , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: FAILED: Patch "mm: avoid unconditional one-tick sleep when swapcache_prepare fails" failed to apply to v6.6-stable tree Date: Tue, 5 Nov 2024 21:09:35 -0500 Message-ID: <20241106020936.168308-1-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 X-Patchwork-Hint: ignore X-stable: review Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 58216C0007 X-Stat-Signature: tyc1g9iwst564p8yot56667t3q5gpwd8 X-HE-Tag: 1730858967-747813 X-HE-Meta: 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 zp/xB69I 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: The patch below does not apply to the v6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From 01626a18230246efdcea322aa8f067e60ffe5ccd Mon Sep 17 00:00:00 2001 From: Barry Song Date: Fri, 27 Sep 2024 09:19:36 +1200 Subject: [PATCH] mm: avoid unconditional one-tick sleep when swapcache_prepare fails 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") Signed-off-by: Barry Song Reported-by: Oven Liyang Tested-by: Oven Liyang Cc: Kairui Song Cc: "Huang, Ying" Cc: Yu Zhao Cc: David Hildenbrand Cc: Chris Li Cc: Hugh Dickins Cc: Johannes Weiner Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Minchan Kim Cc: Yosry Ahmed Cc: SeongJae Park Cc: Kalesh Singh Cc: Suren Baghdasaryan Cc: Signed-off-by: Andrew Morton --- mm/memory.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 3ccee51adfbbd..bdf77a3ec47bc 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4187,6 +4187,8 @@ static struct folio *alloc_swap_folio(struct vm_fault *vmf) } #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ +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. @@ -4199,6 +4201,7 @@ 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; @@ -4297,7 +4300,9 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) * 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_page; } need_clear_cache = true; @@ -4604,8 +4609,11 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) 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, nr_pages); + if (waitqueue_active(&swapcache_wq)) + wake_up(&swapcache_wq); + } if (si) put_swap_device(si); return ret; @@ -4620,8 +4628,11 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) folio_unlock(swapcache); folio_put(swapcache); } - if (need_clear_cache) + if (need_clear_cache) { swapcache_clear(si, entry, nr_pages); + if (waitqueue_active(&swapcache_wq)) + wake_up(&swapcache_wq); + } if (si) put_swap_device(si); return ret; -- 2.43.0