From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7A59E1D9679 for ; Tue, 5 Nov 2024 16:36:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730824594; cv=none; b=qQg5QeOeIcilc5Nr+52GqqEhsdlJMy6xOPTFk8ps7T6AAMjiwUqwLqHR4BY8uJQr8ijDy7br2S0xor6fEiYkEL4L1fwkBzq8Dp4rhpWFy9rC8/quo2zl67KSjGRqHkmNroRrPX3hrR8+6JKbbEpAWQ9qCTGuPD/S7NsXkhIP+Us= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730824594; c=relaxed/simple; bh=60Kw1/W8TtGHXCxcTg5g2AJabXaSCzUdVyj27q490xs=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=Pt1tpiyT9Ofyt6I7mDIyiThj32wUtIMmn4VgJmX+w1Kd6wtz8FyigaSfU8rb7JlJhC/AIgjSLt5d1JgAjLnu91lCOn2oh5NE2mc9VFz5FP/6L3We9O1+4ryekqdLQJTug+/0l+o5wqmF0zp2YsCv+xUt1EL6lDTvF+HFp0KfbRc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=V7Aedqzz; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="V7Aedqzz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A0369C4CECF; Tue, 5 Nov 2024 16:36:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1730824594; bh=60Kw1/W8TtGHXCxcTg5g2AJabXaSCzUdVyj27q490xs=; h=Subject:To:Cc:From:Date:From; b=V7AedqzzmjcueWcHMTNQEamShV5iyWxwjwuDemOuKCys4mS5OXDJaldYqrVwwVWWO yDkVRCguUIEqM6/8ochuT7G2ewP8xOxAfhjQtUj/majGWoi7bxQgcF1j0qxJLcPtIa dz/FS8nj6p40dx30XHP9HuQawRZKyBNLbNT7d3MA= Subject: FAILED: patch "[PATCH] mm: avoid unconditional one-tick sleep when swapcache_prepare" failed to apply to 6.1-stable tree To: baohua@kernel.org,akpm@linux-foundation.org,chrisl@kernel.org,david@redhat.com,hannes@cmpxchg.org,hughd@google.com,kaleshsingh@google.com,kasong@tencent.com,liyangouwen1@oppo.com,mhocko@suse.com,minchan@kernel.org,sj@kernel.org,stable@vger.kernel.org,surenb@google.com,v-songbaohua@oppo.com,willy@infradead.org,ying.huang@intel.com,yosryahmed@google.com,yuzhao@google.com Cc: From: Date: Tue, 05 Nov 2024 17:36:07 +0100 Message-ID: <2024110506-octane-phosphate-f084@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.1-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 . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x 01626a18230246efdcea322aa8f067e60ffe5ccd # git commit -s git send-email --to '' --in-reply-to '2024110506-octane-phosphate-f084@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ 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 diff --git a/mm/memory.c b/mm/memory.c index 3ccee51adfbb..bdf77a3ec47b 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;