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 1C8E9C43458 for ; Tue, 7 Jul 2026 09:22:08 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D81566B00A2; Tue, 7 Jul 2026 05:22:06 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D317C6B00A4; Tue, 7 Jul 2026 05:22:06 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C22C16B00A5; Tue, 7 Jul 2026 05:22:06 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 882D86B00A2 for ; Tue, 7 Jul 2026 05:22:06 -0400 (EDT) Received: from smtpin16.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 12A6F120397 for ; Tue, 7 Jul 2026 09:22:06 +0000 (UTC) X-FDA: 84961439052.16.81A8927 Received: from mail-pj1-f50.google.com (mail-pj1-f50.google.com [209.85.216.50]) by imf28.hostedemail.com (Postfix) with ESMTP id 37CC7C000C for ; Tue, 7 Jul 2026 09:22:04 +0000 (UTC) Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=gmail.com header.s=20251104 header.b=BEtP+4bc; spf=pass (imf28.hostedemail.com: domain of eddyz87@gmail.com designates 209.85.216.50 as permitted sender) smtp.mailfrom=eddyz87@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1783416124; 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=czp6DDn3Tg1L7Caksu341JziUocBqKvToENHXSg/2y4=; b=7WsWYszwqCiIVbrQu/tlWtmaG3MGV8nK3UOSh6f1J/lquPRjGYkNB4f24RpaePl9XE/Kl1 mvouhEYwI89CKAxopxhS3+q6/+lEJSXkfe+Ub03z7FXu+l2MdqcfkaCr1sMjBvtNdEj+wi mmIHd7ig9TbSbZKrTf8Kg8Jmak9LOv8= ARC-Authentication-Results: i=1; imf28.hostedemail.com; dkim=pass header.d=gmail.com header.s=20251104 header.b=BEtP+4bc; spf=pass (imf28.hostedemail.com: domain of eddyz87@gmail.com designates 209.85.216.50 as permitted sender) smtp.mailfrom=eddyz87@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1783416124; b=NyBz/mkhFKvBJX7e2xChq3RNPVA/QCfDwHY18++Ky/ZfuQqKL+VeEpWoGgQqBu9Qg2EsTM zvKWir6B/ttV9geryvtVqLI+eYAkffmn3imurBEtQRJGusPyVrJtoKN/4pOMBVXruaNcSP XnSR1wC7cPOtpdGFXTZhS9Zolq1J7UM= Received: by mail-pj1-f50.google.com with SMTP id 98e67ed59e1d1-3856d6fbcb3so1816513a91.2 for ; Tue, 07 Jul 2026 02:22:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1783416123; x=1784020923; darn=kvack.org; h=mime-version:user-agent:content-transfer-encoding:content-type :references:in-reply-to:date:cc:to:from:subject:message-id:from:to :cc:subject:date:message-id:reply-to:content-type; bh=czp6DDn3Tg1L7Caksu341JziUocBqKvToENHXSg/2y4=; b=BEtP+4bcW85VIwOMz7LFmXMYqB2G68hlpntswD98+ZvbNSB3a+krs2HjaOQYsFGAib miWEd8q2QwFk/AEXBMRpguyzjrhdX9NHWxpJbKs5PVglo6t6gGd0TM+pfeAZXpRHkYOI HGBFNFlM7YMRLDXvpSSSQ/c1+UwyKgJYDaSr104mIMvdyTPzsMoS4UWNdfZWY3wPEEsS uOOpvRps8ilUsHPtjwR2nfByarCLgRoPPViUqxIbCcX43eWvABwnK/gmCtkV2UVZRHGm 8NWNXsqtDsLCa05utso98mr/Fyt8kD4cXt/Fly7ejDEkjlQqr7hmy57MoOYkhjq4xBG4 TB3Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1783416123; x=1784020923; h=mime-version:user-agent:content-transfer-encoding:content-type :references:in-reply-to:date:cc:to:from:subject:message-id:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=czp6DDn3Tg1L7Caksu341JziUocBqKvToENHXSg/2y4=; b=c8Padg8GuXC61jJNzcN4H1xP8bxrKWvJQfozOr4fUb4ieXB4VFKrzpBWXYqf8/TEEc H8VMjyVzSh34T9pX1h3U9YJesPWUfxmFcOk6jqWR4mYW78SI/DRFBpA8Q/f1dDOXn7Zs lv2V6X8EBuYjCHYva3XEAGX83NIQ7pjaGVbZEj2Cz4RY1Xh57Bj/SYLVJJ4X8rpbcR/u RMPdkvdUu261CTLrAX8ItETeHj/mzVX1U9pnTZ+y+JKT3nHBy6Xd1cKDnYtykGXh15aF 3iN36oqdiUR/w+WDiNmMDluSELAdRBDIH0g20OOxkXzkZAELzKkcWhxmPdCBtwVej8m+ 0qaA== X-Forwarded-Encrypted: i=1; AHgh+Rqzzvf5om6ZJfJDVDcxxBSOOAHEcwZXoR8YsRUsxcLLpbihlyCyhMXbPcf/VI1ZiCeRZ88s8L+2rQ==@kvack.org X-Gm-Message-State: AOJu0YxSl1kTuvG9q1eTRdCrjVAXd8qmLKq3KyQ9909USRueBBLHPpyP Os6yFBSCOGbalguWtFwQBGoTeCJdI8ei9EQGAOUSbJY+1crX4b00Q09G X-Gm-Gg: AfdE7ckUQWP1/Xor2P9ILgiLQOI8jb6hHzWFS6mW9X3ehk8luyrwDx+Ha9+DpTRt19v q8A4+RIMjTphBd4bWqYEkATPjKec+ii/TiLQ2fXYFqQiqVg2HLstukMVZzkdVV+UfYoU33pu0rm +JXkkVNirDY5WJuAn0xSzx4X+jhfkSXLrGCMdJs7+HfXGk07v1JfvWC3bSJ3FKKtMJPwwndaetT w0JymfhsYOKXgEpVKqnxtMAvFzDfm5lDw9hozPcpSu35Q96DDmNyUz9zlB0+hzUFQKDYeQHWHqs RJDaS6zuUvfwuS8WKircaRGtb9CBcTGDg2kKaPEn8IcqXFlfJliA/NQDu/zTzQnld2vmGqb/wbX 45zn4BTPS7KPDRmGsiN1DkfNHLMOvS0pj9di97OocOvZsEq/nUW4FD6MxxlgWyqVUQcBro7On16 5BKbMOqTGal4TNKBkwet+bukyHnbPKZc2M6ZXm33D0Ha18qYCINpo= X-Received: by 2002:a17:90b:5350:b0:37f:9cdf:f03d with SMTP id 98e67ed59e1d1-38757894fc7mr4396669a91.32.1783416123050; Tue, 07 Jul 2026 02:22:03 -0700 (PDT) Received: from [192.168.0.13] ([38.34.87.7]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-387d36676easm759200a91.9.2026.07.07.02.22.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Jul 2026 02:22:02 -0700 (PDT) Message-ID: Subject: Re: [PATCH 0/3] selftests/bpf: compare BPF and memory.stat memcg stat readers From: Eduard Zingerman To: Shakeel Butt Cc: Ziyang Men , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Kumar Kartikeya Dwivedi , bpf@vger.kernel.org, Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Shuah Khan , Roman Gushchin , kernel-team@meta.com, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Date: Tue, 07 Jul 2026 02:21:59 -0700 In-Reply-To: References: <20260704045617.487664-1-ziyang.meme@gmail.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2-10 MIME-Version: 1.0 X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 37CC7C000C X-Stat-Signature: 8wyftunagmuak81qqzca8jupkwufz3ck X-HE-Tag: 1783416124-59772 X-HE-Meta: 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 4y9iWwJ+ k1Ich/25+tvjZx5ngQmCzdonN9fru3kpUJfK9yh2LdLn2RnRPs8Ofqi0v+YSbFzQGMzQmiRrHzXDLsJP3A0g+tty9hEZ4aFkWwxMkvan/U2Ylel8mbj/rW/aeUKdDrDq4MODzUErZVncClFraLgIeXvxJSA1lYHMcRNnb+I7KmyZ3D5mxUTwrRuK65BCwGNvSdMrop1Sm2+JBpZmx9xCFwc8/vYdUAvc3I4BIFVu0JbNsqlm6YxkS12+xpvyhE2EC+mK8RHvpv3+Ef5pWmiHFxuOa4UpJgmAFM3Hm2IzLHaM8CgaaJhnUqrYb9ngTxIajEw8QRQWy0EWVzHBZHbiN0YDk44qfiBsaCVz0N3pXGe7rAYkmZmlQ50zBglDYVKmBy1pLcXIPU7LnhR3Up7RA8H3rfUbNRzeaB2N7BaTC6/4zaU0v2J2IHUMPpoCSbo6xsHlYqQsrcLoYuPPiBqT2dn7wehA3D42/RHI0 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 2026-07-06 at 18:50 -0700, Shakeel Butt wrote: > On Mon, Jul 06, 2026 at 05:17:50PM -0700, Eduard Zingerman wrote: > > On Fri, 2026-07-03 at 21:56 -0700, Ziyang Men wrote: > >=20 > > [...] > >=20 > > Hi Ziyang, > >=20 > > I'm a bit hesitant adding 2.5K lines of code to the BPF selftests, > > as this code would need to be (a) maintained, (b) run at each CI invoca= tion. > > Hence, the tests added need to be relevant for the BPF sub-system. > >=20 > > Regarding the benchmarking part, as you state yourself: > >=20 > > =C2=A0 > In my testing (a 60-CPU VM) the BPF path is roughly an order o= f magnitude > > =C2=A0 > faster than the per-cgroup memory.stat parse for a whole-tree = scan, mainly > > =C2=A0 > because it avoids the per-cgroup open/read and string parsing. > >=20 > > With this, I think the benchmarking code can be dropped altogether. > >=20 > > Next, the three memcg_stat_{reader,churn,churn_percpu}.c files share a > > lot of utility code almost verbatim (e.g. tree definition/construction)= . > > Such duplication should be avoided. > >=20 > > Finally, from the BPF point of view the test exercises the following fu= nctionality: > > - kfuncs: > > =C2=A0 - bpf_mem_cgroup_page_state > > =C2=A0 - bpf_mem_cgroup_vm_events > > =C2=A0 - bpf_put_mem_cgroup > > =C2=A0 - bpf_get_mem_cgroup > > - main iterator logic. > >=20 > > All kfuncs but bpf_get_mem_cgroup() are thin wrappers around mm/memcont= rol.c code, > > all kfuncs including the bpf_get_mem_cgroup() are already exercised in = the selftests. > > The iterator logic itself is covered by 8 sub-tests in the prog_tests/c= group_iter.c. > > Hence two questions: > > - What do these new tests add in terms of tests coverage? > > - Why do BPF selftests need to exercise the churn and churn_percpu scen= arios? > >=20 > > Shakeel, could you please comment as well? >=20 > Hi Eduard, >=20 > Thanks a lot for taking a look. The main motivation I had behind requesti= ng > Ziyang to send this series (beside making him learn the tooling and proce= ss of > sending patches to lkml) was to have a reference implementation and perfo= rmance > comparison for BPF based cgroup/memcg stats collection. >=20 > However you have correctly pointed out that selftests might not be the ri= ght > place for such kind of code as selftests are more focused on functional t= ests > and run by a lot of CIs while this is a performance benchmarking code. >=20 > I am wondering if there is a place for this benchmarking code in kernel u= nder > tools folder but archiving it on lkml might be good enough and should be = easily > searchable. Anyways thanks again for your time. Hi Shakeel, We do have bpf benchmarks in the kernel tree, the entry point is tools/testing/selftests/bpf/bench.c. These are supposed to be performance measurements and are executed manually from time to time (quite rarely, as far as I understand), not by CI. However, if I understand Ziyang's assessment correctly, this code is not really a performance test, but kind of a load test. Thanks, Eduard