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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0DA9AC04A6A for ; Fri, 4 Aug 2023 16:37:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230192AbjHDQhX (ORCPT ); Fri, 4 Aug 2023 12:37:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48712 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229815AbjHDQhV (ORCPT ); Fri, 4 Aug 2023 12:37:21 -0400 Received: from mail-qv1-xf29.google.com (mail-qv1-xf29.google.com [IPv6:2607:f8b0:4864:20::f29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 18FFC195 for ; Fri, 4 Aug 2023 09:37:19 -0700 (PDT) Received: by mail-qv1-xf29.google.com with SMTP id 6a1803df08f44-63cfa3e564eso13786736d6.0 for ; Fri, 04 Aug 2023 09:37:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cmpxchg-org.20221208.gappssmtp.com; s=20221208; t=1691167038; x=1691771838; 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=iUJy9CxyJyDezGa57jwVulgOP6Mhmh9lxMHoUFNxQOg=; b=N8zywGIpRTGhPC/hd5Uaa9XnP65QfObz3MOaQDHYBSgg96x0lu4ubKHgZyvQjRg+92 VimNYt6Qi+T2OSX2whxjKdAwU5/KjPFJAJ8FQDdIS6jXwklryXprXrKQGXj9+OlCaDkz 3BPikSVV1zG++16OImjNF+EnR6jfDlpZjFzRRbEI2TKM1ALXkZgWSYisS9iRkCf9uPpL wBCvyMsghryoppGBxdYYnIv8JITuv327O30KANkFj9SkQRGLPKdUnIYxkMPnuCb+6MV2 utPvzU/Zd0n7b7YmTIV2gNEhgfjpPjenS3EcryRbLfQHd44dgYs/kyhVn6CXzmHTcpuN jP0w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1691167038; x=1691771838; 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=iUJy9CxyJyDezGa57jwVulgOP6Mhmh9lxMHoUFNxQOg=; b=Q38IVRCl6brupI/d2wXFri/VvyhrrWp6nPqafCmgrqQVkxzbosVSLRsbtyLNvIXWe5 BaE7TVuyChGdjlC5xQn1NwUXx3Njbi+q+hO0G4FaKzxwSIWUjwPawICJ3mpMuzeKlVxC WHEgDZukEz2uq+hisIdzWQqR+er5zYBjZ8q6MMZjjpxKzntPQvpA1QchatJg4ZhEnrC4 OYnPyDTF+pQCGAYDWtDgAbDTMdEYn2oV8DOJnHx4AmJ9rhapIgNeiGNMDnzrGy5Tq9On V0FHUuFgrINbBcfAxqmHlVIHHiYvJLzC2QzZcvknWObDyLFX7gSFR8tbotazbhO8/zB1 aGjg== X-Gm-Message-State: AOJu0YwAInqmTZ+M2pZuXebXsQsQKUg6Vdzu1q6S19qA06XCOEL+bpo9 UiycLbsJIefHxPCWH/imdslKcA== X-Google-Smtp-Source: AGHT+IGvEQu5HgCOytuEIOWYX6CR56Y/2e5JSlxsagFnROkz1i4u6xSjaOns8WHVi48AGsOpTahDqQ== X-Received: by 2002:a0c:e10a:0:b0:62d:f806:7f80 with SMTP id w10-20020a0ce10a000000b0062df8067f80mr2235164qvk.13.1691167038197; Fri, 04 Aug 2023 09:37:18 -0700 (PDT) Received: from localhost ([2620:10d:c091:400::5:9910]) by smtp.gmail.com with ESMTPSA id e29-20020a0cb45d000000b00632266b569esm782221qvf.87.2023.08.04.09.37.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Aug 2023 09:37:17 -0700 (PDT) Date: Fri, 4 Aug 2023 12:37:16 -0400 From: Johannes Weiner To: Lucas Karpinski Cc: Andrew Morton , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Tejun Heo , Zefan Li , Shuah Khan , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] selftests: cgroup: fix test_kmem_memcg_deletion false positives Message-ID: <20230804163716.GA337691@cmpxchg.org> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 04, 2023 at 11:37:33AM -0400, Lucas Karpinski wrote: > The test allocates dcache inside a cgroup, then destroys the cgroups and > then checks the sanity of numbers on the parent level. The reason it > fails is because dentries are freed with an RCU delay - a debugging > sleep shows that usage drops as expected shortly after. > > Insert a 1s sleep after completing the cgroup creation/deletions. This > should be good enough, assuming that machines running those tests are > otherwise not very busy. This commit is directly inspired by Johannes > over at the link below. > > Link: https://lore.kernel.org/all/20230801135632.1768830-1-hannes@cmpxchg.org/ > > Signed-off-by: Lucas Karpinski Maybe I'm missing something, but there isn't a limit set anywhere that would cause the dentries to be reclaimed and freed, no? When the subgroups are deleted, the objects are just moved to the parent. The counters inside the parent (which are hierarchical) shouldn't change. So this seems to be a different scenario than test_kmem_basic. If the test is failing for you, I can't quite see why.