From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 746B3C44512 for ; Mon, 20 Jul 2026 02:28:03 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 458E46B0093; Sun, 19 Jul 2026 22:28:02 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3E2CB6B0095; Sun, 19 Jul 2026 22:28:02 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 31F756B0096; Sun, 19 Jul 2026 22:28:02 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 089026B0093 for ; Sun, 19 Jul 2026 22:28:01 -0400 (EDT) Received: from smtpin22.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 60DB5160735 for ; Mon, 20 Jul 2026 02:28:01 +0000 (UTC) X-FDA: 85007569962.22.2B8C1AF Received: from out-176.mta1.migadu.com (out-176.mta1.migadu.com [95.215.58.176]) by imf27.hostedemail.com (Postfix) with ESMTP id 1C49140006 for ; Mon, 20 Jul 2026 02:27:58 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=eNR5XIKw; spf=pass (imf27.hostedemail.com: domain of qi.zheng@linux.dev designates 95.215.58.176 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1784514479; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=AlNhtQCquztP9G9X9Z8iMtH1eSwOYMw8dTp0ZlM181c=; b=5DjSoO9Cdl46sbaItS4zlIAobi4knf7m5D3aumSqINxLxLbR6k9aFwrhJCDPNJ0Gyul0n9 yhRRTDlQzCO7LJq3lfwGaxyp7C8IawdC7tgnmEzOqaGtsWfMrwmiU85zvBPB0LHIAKNEUg dHhgo8ysSiWZx8oE2waPfRahA7nZsRw= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=eNR5XIKw; spf=pass (imf27.hostedemail.com: domain of qi.zheng@linux.dev designates 95.215.58.176 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1784514479; b=6zqXio7crNQSLnxtE+ykAMMO6awv3G7vqeEHQBNvaBvDInr38XUnviLLGuOIjFaLtDtkNK gLuRWcUVEsPkgPoD5pqxcD6W+TOg5eJNYB+2AYvzXdt+2000pV0Y6Las0y10/qXPtptCMN iLGLFTLtqyxLAom6kSLHczYEe+Tm2j8= Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1784514477; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=AlNhtQCquztP9G9X9Z8iMtH1eSwOYMw8dTp0ZlM181c=; b=eNR5XIKwOUOOp9+tzPCT94JJoXfglAFyTLkEo6lbTOBL7ZmigdZfbK5O+mg/9ghIFh9eBs PW6Mv+3DKHv2p3XIvxukoaCbKBlc0/6zNPw7hJrLWoMq27RNj4Bqk5zw9RYzX1dUUVPpi4 763PxCA35hA5D2IQaHJMS9Q+06zHa3Y= Date: Mon, 20 Jul 2026 10:27:43 +0800 MIME-Version: 1.0 Subject: Re: [PATCH v2 1/4] mm/vmscan: fix anon-only reclaim evicting file pages when swappiness=max To: Ridong Chen , akpm@linux-foundation.org Cc: hannes@cmpxchg.org, david@kernel.org, mhocko@kernel.org, shakeel.butt@linux.dev, ljs@kernel.org, kasong@tencent.com, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, hezhongkun.hzk@bytedance.com, muchun.song@linux.dev, dave@stgolabs.net, roman.gushchin@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Ridong Chen References: <20260718095251.82937-1-ridong.chen@linux.dev> <20260718095251.82937-2-ridong.chen@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Qi Zheng In-Reply-To: <20260718095251.82937-2-ridong.chen@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 1C49140006 X-Stat-Signature: tuy7gsoq8uerwztrocsuc8kudpxori7x X-HE-Tag: 1784514478-666688 X-HE-Meta: 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 QZEfVZFS 8QflF3T0HLGaEk3gQwurGovLkkQSXIVPJuyEc0QRoLwyg0pCgIPjgkxJ6RW0WrKPzINX9iXtBI8oUuD/gHeJU0tBQq46VyU0tXm/2w1ue1OXk7UOi8NdkD5qxyVBlmtoaSymSVep+GX+OH/OP5lQ4o3inUnIHQzhRT/LEug5Hxke0ZHAW3///m7shwffg1XZCxCrwnODgMaXygsg5RDGxgft6fRKIpTIaXV/ndeqKt55/HunoUuWlO6FMNU6cLuoDjm4oEeFwtOx2BfdsAnxnKMN1reuhuM7ogPHfuk45LTEMw9lAuVx1vz7+aIhSkf6Y7U47 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/18/26 5:52 PM, Ridong Chen wrote: > From: Ridong Chen > > As Qi mentioned [1], when swappiness=max (SWAPPINESS_ANON_ONLY) is set, > the reclaim logic is expected to reclaim anonymous pages exclusively. > However, due to the current ordering of checks in get_scan_count(), > file pages may still be evicted if can_reclaim_anon_pages() returns > false, which contradicts the semantics of SWAPPINESS_ANON_ONLY. > > Reproducer in a cgroup holding 64M of file cache, with no swap configured: > > Before (file cache is wrongly evicted): > # cat memory.stat > anon 196608 > file 67178496 > pgscan_proactive 0 > # echo "64M swappiness=max" > memory.reclaim > # cat memory.stat > anon 208896 > file 4096 <- page cache evicted > pgsteal_proactive 16400 > pgscan_proactive 16400 > > After (file cache is left intact): > # cat memory.stat > anon 200704 > file 67178496 > pgscan_proactive 0 > # echo "64M swappiness=max" > memory.reclaim > -bash: echo: write error: Resource temporarily unavailable > # cat memory.stat > anon 208896 > file 67178496 <- page cache untouched > pgsteal_proactive 0 > pgscan_proactive 0 > > Fix this by bailing out early when SWAPPINESS_ANON_ONLY is set and no > anonymous pages are reclaimable, before falling back to file reclaim. > > [1] https://lore.kernel.org/cgroups/7ddf3eee-5fe2-45f7-8614-c8936a039e04@linux.dev/ > > Fixes: 68a1436bde00 ("mm: add swappiness=max arg to memory.reclaim for only anon reclaim") > Suggested-by: Qi Zheng > Acked-by: Shakeel Butt > Acked-by: Johannes Weiner > Reviewed-by: Muchun Song > Signed-off-by: Ridong Chen > --- > mm/vmscan.c | 18 +++++++++++------- > 1 file changed, 11 insertions(+), 7 deletions(-) Thanks for the fix! Reviewed-by: Qi Zheng > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 35c3bb15ae96..d6b383d96a0c 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2501,6 +2501,17 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc, > enum scan_balance scan_balance; > enum lru_list lru; > > + /* Proactive reclaim initiated by userspace for anonymous memory only */ > + if (swappiness == SWAPPINESS_ANON_ONLY) { > + WARN_ON_ONCE(!sc->proactive); > + if (!can_reclaim_anon_pages(memcg, pgdat->node_id, sc)) { > + memset(nr, 0, sizeof(*nr) * NR_LRU_LISTS); > + return; > + } > + scan_balance = SCAN_ANON; > + goto out; > + } > + > /* If we have no swap space, do not bother scanning anon folios. */ > if (!sc->may_swap || !can_reclaim_anon_pages(memcg, pgdat->node_id, sc)) { > scan_balance = SCAN_FILE; > @@ -2519,13 +2530,6 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc, > goto out; > } > > - /* Proactive reclaim initiated by userspace for anonymous memory only */ > - if (swappiness == SWAPPINESS_ANON_ONLY) { > - WARN_ON_ONCE(!sc->proactive); > - scan_balance = SCAN_ANON; > - goto out; > - } > - > /* > * Do not apply any pressure balancing cleverness when the > * system is close to OOM, scan both anon and file equally