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]) by smtp.lore.kernel.org (Postfix) with ESMTP id BEF87C369A2 for ; Mon, 14 Apr 2025 18:01:49 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B095D28006F; Mon, 14 Apr 2025 14:01:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AB6AF28005A; Mon, 14 Apr 2025 14:01:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9578528006F; Mon, 14 Apr 2025 14:01:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 723DC28005A for ; Mon, 14 Apr 2025 14:01:48 -0400 (EDT) Received: from smtpin24.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 10EE514054F for ; Mon, 14 Apr 2025 18:01:48 +0000 (UTC) X-FDA: 83333417496.24.61F07C9 Received: from mail-wr1-f44.google.com (mail-wr1-f44.google.com [209.85.221.44]) by imf15.hostedemail.com (Postfix) with ESMTP id 16DF1A000D for ; Mon, 14 Apr 2025 18:01:45 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=suse.com header.s=google header.b=Rriu1UtS; dmarc=pass (policy=quarantine) header.from=suse.com; spf=pass (imf15.hostedemail.com: domain of mkoutny@suse.com designates 209.85.221.44 as permitted sender) smtp.mailfrom=mkoutny@suse.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1744653706; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=nBLuWbdtMel6i38ax54FckIfRTO54jFDOdfOeU/b1uA=; b=lmu2vMyhtAx2DQGFrkArH5LEESLjZwHokPnz09v1JsSiNJmf8NeRsgIGHUEoGcVgLMr9DF iFcOVzbkTASkgHiJcZGlUFoOzrwdFGsUoukqXh6935k/SgI878EDQBapYWIlsvjGmmksGH BB2pBQmiKS5E6JSOHqhdsfuHIGdoMJU= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=suse.com header.s=google header.b=Rriu1UtS; dmarc=pass (policy=quarantine) header.from=suse.com; spf=pass (imf15.hostedemail.com: domain of mkoutny@suse.com designates 209.85.221.44 as permitted sender) smtp.mailfrom=mkoutny@suse.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1744653706; a=rsa-sha256; cv=none; b=QG7UjpanyWSYtR7WIkS5PHpy9TDV0NAyqrV0xKy8A8G2vcU47sMMJldEBlFVHLlCHMiW0/ DOUtWwTTaRRe0fspwEEvdSsolyKEeVhEHHAPZ4+Bg6FaPuEEgOyT55B6NYKNDwgmBlMvYk N49mQGC7J0BbG98/kzpOhQBhHSg7WeU= Received: by mail-wr1-f44.google.com with SMTP id ffacd0b85a97d-39c31e4c3e5so2917617f8f.0 for ; Mon, 14 Apr 2025 11:01:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=google; t=1744653704; x=1745258504; darn=kvack.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=nBLuWbdtMel6i38ax54FckIfRTO54jFDOdfOeU/b1uA=; b=Rriu1UtSJ7xONNafbPNtwADX1Y31p9sQOd+Ll//b0p6Yf4RSS/lFLHNUP6KQXRSvE1 fx4aX5dDRkTuJrVcHeCHdShoAw3ZaMSNlDH02zxgjtYL0IBwSmAz/iVsQ2LtWTdAdB9E v16bDsJ4DhABl5Zznjxp5UeFUxT6DlsgU6mb5HPYH/up7y6sZf2z4zUjHdooFQW+KA4e fm5LEImKVEteM7AnJByGfkK/QFflUoH2JriNPhLWOx+gsdRWNwWQU2fq8GeX/+R4HCWo rSB705+u8npO+LETBOF7m+f6vXWd/aH1CFIcJoxx16WhKRaKj2f8XOY2KeEBMgTf2gWH 5B2Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1744653704; x=1745258504; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=nBLuWbdtMel6i38ax54FckIfRTO54jFDOdfOeU/b1uA=; b=hKCiWMU0/9PW2TbrTP4VCp6hocX0fsPwxZ9gw3/92A3VgyZDhqLAKJ1guRQ9GiI6aQ 9hGXMuAPXi37pls9bX6ae3OpRewNpg1DVtgWdWQCQ9WdbaEn+AYlJUqESkbL6+6FFDoe o8hQBm+3p4Bo7eG3sJls80w6PLHLW8z4RYpjVcYfZ36Q/wi/iFpRQlIEIQSbdK3Lkz4C IhKOnG5K+0kflzO0BK8wa9k8wqPU6+QgCjyBFxB07f4QAuamTJ1msTggKwmpCWynSH3Q X1bQb3d2UOdV0M6sL5s8mDoacVZJ48W06UsHHM9sXAaWjLZWBOgXVlhyRLgXScOq/cfg NPfA== X-Forwarded-Encrypted: i=1; AJvYcCUXht8AdRDwUQLZQOsuBMJO2ZOYZHLi8t+5/z7rGByOBB7FHHcsAZ3arslkU/3uIt5zJ23DW04XXg==@kvack.org X-Gm-Message-State: AOJu0YyTe5toQ+Ju/Nv3W1l2q8NoHAKvV+WrDtm8kUx1D/TxeDzPZyVZ QQGXBVc5snvWVtiWbLxnoijzUF8YoTfWLIxU1gUIfFF3FQy43mcYfYeUBxWpjt4= X-Gm-Gg: ASbGncv3gNfTEX8ZFz6yexhddpocVQ75Hz9eXgFboFuOh9j1hlTLNk/52F9Ez5ytRwn hcEbzgVC85Xp5DBYNv++qaFpfziOsWd/iPBoB1c+6BQ0NbC1ZcAHPH/U5ChxFqEieepZ1vTCGLb PW6+RAKKWJ73tK+YAbkkvO0vYokK8fpZbug6P5blcIUgfWC/WEMOplHvXJhHk6IukxHJA61tE4u 69HXD32w0w+wRpowDYpfVAEiKhyM9d3PJ3EG8wPvmnEUN5WeCiIjIogT0GoQhKnS29oeS8UbcEn AD+1vfn3gwCsTbl4ACEwh0Xc66crWfFl561Wh5lSFJ4= X-Google-Smtp-Source: AGHT+IEtQycgr4S3+PgCeHikW/Hyvr38HbspTFMfglvu/9qnMU6MbIV/XlhPDnBnlVxtCbAFfxNM+w== X-Received: by 2002:a5d:598e:0:b0:39c:3122:ad55 with SMTP id ffacd0b85a97d-39ea51f5b0dmr9250849f8f.18.1744653704398; Mon, 14 Apr 2025 11:01:44 -0700 (PDT) Received: from blackdock.suse.cz ([193.86.92.181]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-39eae978023sm11710271f8f.47.2025.04.14.11.01.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Apr 2025 11:01:43 -0700 (PDT) Date: Mon, 14 Apr 2025 20:01:42 +0200 From: Michal =?utf-8?Q?Koutn=C3=BD?= To: Johannes Weiner Cc: Waiman Long , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Tejun Heo , Shuah Khan , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v6 1/2] mm/vmscan: Skip memcg with !usage in shrink_node_memcgs() Message-ID: References: <20250414021249.3232315-1-longman@redhat.com> <20250414021249.3232315-2-longman@redhat.com> <6572da04-d6d6-4f5e-9f17-b22d5a94b9fa@redhat.com> <20250414164721.GA741145@cmpxchg.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="s2v2mxjanhgmijod" Content-Disposition: inline In-Reply-To: <20250414164721.GA741145@cmpxchg.org> X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 16DF1A000D X-Stat-Signature: os3krxk7k34i457c9t3mqygkpq7r7myz X-Rspam-User: X-HE-Tag: 1744653705-319100 X-HE-Meta: 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 IqUwJnSz 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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: --s2v2mxjanhgmijod Content-Type: text/plain; protected-headers=v1; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH v6 1/2] mm/vmscan: Skip memcg with !usage in shrink_node_memcgs() MIME-Version: 1.0 On Mon, Apr 14, 2025 at 12:47:21PM -0400, Johannes Weiner wrote: > It's not a functional change to the protection semantics or the > reclaim behavior. Yes, that's how I understand it, therefore I'm wondering what does it change. If this is taken: if (!mem_cgroup_usage(memcg, false)) continue; this would've been taken too: if (mem_cgroup_below_min(target_memcg, memcg)) continue; (unless target_memcg =3D=3D memcg but that's not interesting for the events here) > The problem is if we go into low_reclaim and encounter an empty group, > we'll issue "low-protected group is being reclaimed" events, How can this happen when page_counter_read(&memcg->memory) <=3D memcg->memory.emin ? (I.e. in this case 0 <=3D emin and emin >=3D 0.) > which is kind of absurd (nothing will be reclaimed) and thus confusing > to users (I didn't even configure any protection!) Yes. =20 > I suggested, instead of redefining the protection definitions for that > special case, to bypass all the checks and the scan count calculations > when we already know the group is empty and none of this applies. >=20 > https://lore.kernel.org/linux-mm/20250404181308.GA300138@cmpxchg.org/ Is this non-functional change to make shrink_node_memcgs() robust against possible future redefinitions of mem_cgroup_below_*()? Michal --s2v2mxjanhgmijod Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQTd6mfF2PbEZnpdoAkt3Wney77BSQUCZ/1NhAAKCRAt3Wney77B SRqTAP9ceEwBCy9asOHNELiBKAgokXBXGmLAsJ7NOFiKLG7XAgD/WuDqfbDSlDL8 jqWttQx7fV7ktBUPZ6qqN4+sjbp5fgE= =UgxG -----END PGP SIGNATURE----- --s2v2mxjanhgmijod--