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 413D2C3601E for ; Mon, 7 Apr 2025 14:36:19 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B8E8E6B0008; Mon, 7 Apr 2025 10:36:17 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B3DD26B000C; Mon, 7 Apr 2025 10:36:17 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9DC166B000D; Mon, 7 Apr 2025 10:36:17 -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 815716B0008 for ; Mon, 7 Apr 2025 10:36:17 -0400 (EDT) Received: from smtpin09.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 22B71C061E for ; Mon, 7 Apr 2025 14:36:18 +0000 (UTC) X-FDA: 83307498036.09.A4FA87F Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf18.hostedemail.com (Postfix) with ESMTP id BB8A51C0006 for ; Mon, 7 Apr 2025 14:36:15 +0000 (UTC) Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b="ekZe/U02"; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf18.hostedemail.com: domain of llong@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=llong@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1744036575; 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=x5DJg/Yndiod0rCSXdIIJltN9dcYDMLjV18CCekaRB0=; b=SOtCeGrq1XdYmtJN76Nmd2KcrFohwRndnnln54dCu31ctc110hG9cR9mIRG/XK2fvzSGG3 CpJW44dWfo/RMbCv3jGblUJc7z0aL5fndqp0JCn75f7Wn4u++F+GEYa1NvOWS919MrtEi5 k6r6Yao+SGqqBL219BirvPOryhMYh3A= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b="ekZe/U02"; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf18.hostedemail.com: domain of llong@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=llong@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1744036575; a=rsa-sha256; cv=none; b=gpXjUJ0UeWUou/gZR8GNh7Fd0IITX2wYBbMTXAzZuK9TQqAy2MwihIuC5NBa7Zd36JuQkz rKXpj9bOrquGqKuVIwr0sX+pnExLzMpKCvECqT6fH2PWFr2Nf7KBHG5h6W4ugnvQa+aXhN fJlv1ljHgbImsXpfUatH3RfNEQyUUL8= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1744036575; 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=x5DJg/Yndiod0rCSXdIIJltN9dcYDMLjV18CCekaRB0=; b=ekZe/U02PBCisSWVvVqMB215fNSHdWW+L+mWhGQKfpbCcDHnBNjXHoaV92fnMIZJeloE/x 1TBBuyWDKskN7TdpyGslWW2MgeNRhoa+84IvH6TIt2Mr7ilV6z7WH1/VfwFPNBM1EcrvY0 NjKkmuxvQg5GJ36GAY+HmEK0r9Z7qQ8= Received: from mail-qv1-f72.google.com (mail-qv1-f72.google.com [209.85.219.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-368-AH5JUfxHMpObQ9gwxLqsvw-1; Mon, 07 Apr 2025 10:36:11 -0400 X-MC-Unique: AH5JUfxHMpObQ9gwxLqsvw-1 X-Mimecast-MFC-AGG-ID: AH5JUfxHMpObQ9gwxLqsvw_1744036571 Received: by mail-qv1-f72.google.com with SMTP id 6a1803df08f44-6e8f9057432so91153086d6.1 for ; Mon, 07 Apr 2025 07:36:11 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1744036571; x=1744641371; h=content-transfer-encoding:in-reply-to:content-language:references :cc:to:subject:user-agent:mime-version:date:message-id:from :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=x5DJg/Yndiod0rCSXdIIJltN9dcYDMLjV18CCekaRB0=; b=rrcgLiKIC/HzO7uNjNqwoe6dbVyV7H8Br6HySutNHqOVshptu+liriZlUQCDNA6V/U Wv0d+4jRwSechfO+fvfi6jkqAWLo92Ltxs9JuOdV6AIrDP54CJBNza7vksnxodIl0fXz zu5oiKOGMSf37M+P3h6GRKcGvtneCgq447VFnfFTd//bTAex10o7H9OU68SUt8jcM3kG Vrh8IavQhx6bJAbjNgz/BgTWYSvYI4uaOsjIpZoKmuXDZXEhDcbPyorIiBao1eXo44iJ KMVuk/vrXcY29CzjALEjlnvlFp7NCl/d7Wq9YZ/Fk5DQEr7Wjs4iOMVAMZ2NGdXlL4yS dDTQ== X-Forwarded-Encrypted: i=1; AJvYcCXGAu1gcHHhh5e4aEoyMTEfws4L5JFy3LdIGry8UAsdBjySG5VBLOo6PFHaD3m5j0ukm/nP5cC1GA==@kvack.org X-Gm-Message-State: AOJu0Yw1yrHcoDyWJZQuxHNisYp4lvSp5TKGBns+CAfvEGhERe2BCua9 pXiRBNTIwmaL/12fRUjpuzq6oO8fYaVjvAkbATPe9SXztT64xxOHZyAOZgO3O83ElwKhy4fzeBy BU2Z6q4Wt0LeF6QG6T3hEnXYoXOizqUKPbl56vcEeLkO9fNJ9 X-Gm-Gg: ASbGnctHEJmfyKCVWZbC8hntylajYygCKtl/WOWNqGKlxN94VVjaNfVPt+Hz51IeKpf 9LL5a5eTt/LCgGQgphphWUkhLaDHW8ZuLSHMU+pfixDXIm3rOYwJPy7PYQMDBqtk+p58Jzj+FOc AVBjeBAs99wzTYT03RhpCko0m7z1DKw+NEKP4yJg8eJi89pqnUKsWcmdj5ZzTagPKNQ4rsGBryO gMWvkmLINBKeN5cQ+Qz3xQJauqOnedyn31grE145mSVWLAX2WxCW/+8c/pOdRUB3g1zCJtp4Nio aGl34zD0UjCQ4k91nrxtZQjDuaVK3CUfRUUWnlhuKE4vc0SfZQZuQX6eaxjUTA== X-Received: by 2002:a05:6214:5189:b0:6e8:fb92:dffa with SMTP id 6a1803df08f44-6f012e1adf0mr219540316d6.25.1744036571317; Mon, 07 Apr 2025 07:36:11 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEBjeFW6/Zy3PCGjK+e4ng1QFrOqWTfMoNnO69ymICNu5TBJyk/4flMbpzGbuBr1A3OzyWJBA== X-Received: by 2002:a05:6214:5189:b0:6e8:fb92:dffa with SMTP id 6a1803df08f44-6f012e1adf0mr219539506d6.25.1744036570672; Mon, 07 Apr 2025 07:36:10 -0700 (PDT) Received: from ?IPV6:2601:188:c100:5710:315f:57b3:b997:5fca? ([2601:188:c100:5710:315f:57b3:b997:5fca]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6ef0f14cf41sm58909196d6.105.2025.04.07.07.36.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 07 Apr 2025 07:36:10 -0700 (PDT) From: Waiman Long X-Google-Original-From: Waiman Long Message-ID: <2d50bccb-9cb9-4f28-a8a6-116b2003acd2@redhat.com> Date: Mon, 7 Apr 2025 10:36:09 -0400 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 1/2] mm/vmscan: Skip memcg with !usage in shrink_node_memcgs() To: Johannes Weiner Cc: Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Tejun Heo , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Shuah Khan , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org References: <20250407014159.1291785-1-longman@redhat.com> <20250407014159.1291785-2-longman@redhat.com> <20250407142455.GA827@cmpxchg.org> In-Reply-To: <20250407142455.GA827@cmpxchg.org> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: N8THBewCf5fwyHGh9Q3XZM10GgEwsJup6FHWdq89apU_1744036571 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam01 X-Stat-Signature: pyjd8ietfp3k1g1a3eengwougakxdu8s X-Rspam-User: X-Rspamd-Queue-Id: BB8A51C0006 X-HE-Tag: 1744036575-439726 X-HE-Meta: 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 lFeOOdvG 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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: On 4/7/25 10:24 AM, Johannes Weiner wrote: > On Sun, Apr 06, 2025 at 09:41:58PM -0400, Waiman Long wrote: >> The test_memcontrol selftest consistently fails its test_memcg_low >> sub-test due to the fact that two of its test child cgroups which >> have a memmory.low of 0 or an effective memory.low of 0 still have low >> events generated for them since mem_cgroup_below_low() use the ">=" >> operator when comparing to elow. >> >> The two failed use cases are as follows: >> >> 1) memory.low is set to 0, but low events can still be triggered and >> so the cgroup may have a non-zero low event count. I doubt users are >> looking for that as they didn't set memory.low at all. >> >> 2) memory.low is set to a non-zero value but the cgroup has no task in >> it so that it has an effective low value of 0. Again it may have a >> non-zero low event count if memory reclaim happens. This is probably >> not a result expected by the users and it is really doubtful that >> users will check an empty cgroup with no task in it and expecting >> some non-zero event counts. >> >> In the first case, even though memory.low isn't set, it may still have >> some low protection if memory.low is set in the parent. So low event may >> still be recorded. The test_memcontrol.c test has to be modified to >> account for that. >> >> For the second case, it really doesn't make sense to have non-zero >> low event if the cgroup has 0 usage. So we need to skip this corner >> case in shrink_node_memcgs() by skipping the !usage case. The >> "#ifdef CONFIG_MEMCG" directive is added to avoid problem with the >> non-CONFIG_MEMCG case. >> >> With this patch applied, the test_memcg_low sub-test finishes >> successfully without failure in most cases. Though both test_memcg_low >> and test_memcg_min sub-tests may still fail occasionally if the >> memory.current values fall outside of the expected ranges. >> >> Suggested-by: Johannes Weiner >> Signed-off-by: Waiman Long >> --- >> mm/vmscan.c | 10 ++++++++++ >> tools/testing/selftests/cgroup/test_memcontrol.c | 7 ++++++- >> 2 files changed, 16 insertions(+), 1 deletion(-) >> >> diff --git a/mm/vmscan.c b/mm/vmscan.c >> index b620d74b0f66..65dee0ad6627 100644 >> --- a/mm/vmscan.c >> +++ b/mm/vmscan.c >> @@ -5926,6 +5926,7 @@ static inline bool should_continue_reclaim(struct pglist_data *pgdat, >> return inactive_lru_pages > pages_for_compaction; >> } >> >> +#ifdef CONFIG_MEMCG >> static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc) >> { >> struct mem_cgroup *target_memcg = sc->target_mem_cgroup; >> @@ -5963,6 +5964,10 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc) >> >> mem_cgroup_calculate_protection(target_memcg, memcg); >> >> + /* Skip memcg with no usage */ >> + if (!page_counter_read(&memcg->memory)) >> + continue; > Please use mem_cgroup_usage() like I had originally suggested. > > The !CONFIG_MEMCG case can be done like its root cgroup branch. Will do that. > >> if (mem_cgroup_below_min(target_memcg, memcg)) { >> /* >> * Hard protection. >> @@ -6004,6 +6009,11 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc) >> } >> } while ((memcg = mem_cgroup_iter(target_memcg, memcg, partial))); >> } >> +#else >> +static inline void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc) >> +{ >> +} >> +#endif /* CONFIG_MEMCG */ > You made the entire reclaim path a nop for !CONFIG_MEMCG. Yes, that is probably not right. Will fix that. Cheers, Longman