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 X-Spam-Level: X-Spam-Status: No, score=-18.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1036CC433ED for ; Fri, 14 May 2021 18:50:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E042761454 for ; Fri, 14 May 2021 18:50:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231336AbhENSvg (ORCPT ); Fri, 14 May 2021 14:51:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54570 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231330AbhENSvf (ORCPT ); Fri, 14 May 2021 14:51:35 -0400 Received: from mail-yb1-xb30.google.com (mail-yb1-xb30.google.com [IPv6:2607:f8b0:4864:20::b30]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 56BDCC06174A for ; Fri, 14 May 2021 11:50:18 -0700 (PDT) Received: by mail-yb1-xb30.google.com with SMTP id c14so315108ybr.5 for ; Fri, 14 May 2021 11:50:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=+muSPPrBFQS9BSc0XLvqjbGXmXt1qzS3v/wikaP3SFA=; b=cwimqVsxRhMfLl3BUVdKOfBuVUWCAaEwy2N+oSpdJihUEyOv8KKE9wmrwBugETu4Cj kAd6i6KkaTWyq3+xAesgB78ZLsomdzHKjUXLyq8QjJWV699jE//SYZ5t+qj9oGmbQb+l /n4+uqQtvp119b5o+bzYd/ZXfdyUDJG+tfJgKObJvZlSWmIdFo+ClW8Zq1X1gXgYIiZO pvabe/l9/8HvLZVMbg6T53jeQfdupvP/ZLB10YmnZHUQm3ezR7yNEk1WsBfSTKa668k0 36W1W3jvk4s0ju35RM4z7N7RkN8ipSFlYIkFzc6G1ssd60DJm0j9WY1TXAmzJgNqcTeE 7m0w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=+muSPPrBFQS9BSc0XLvqjbGXmXt1qzS3v/wikaP3SFA=; b=aiToNOA6IuX7ElIXqlodqhug0ZWYXUDLiYglO43w9MxrIzgCjHZsckEMUm64QLa0J7 eu1IalvzDbfrBW449brIn8YxXAsdUPBym49RuF3iW6Y9Fz7qjfsjqak+RAl42QVF3ovO 5RmQGbpkVTpKI5cSOYd6RLLNCOkG26v2M8w/Sr4MSIebv80M7BDluc9O0mryw9e4PYHh WUGbtU3p5VWkwEDUri6U7bl6YkF86ikgW7ydg5oaKyfmPzksIk3QtsvpsN0mxz7qFCtj 7h+TNqJG0SztwPE3LUJw260tmTFt28NbSR344K/ncSFx11UQTpHyibjJng2sp0Y2mqhD ls8w== X-Gm-Message-State: AOAM532NojJQnhUWDNLoN/E++3W8Bfyn8n4vFRzwzLdY22bMnd6vReAu iPwvktycJyKtnNC4lKGzdCsie4yO6Wg7zyg9pQXr7g== X-Google-Smtp-Source: ABdhPJwd0ZOJ0DFc9TcGosPgVAj7cAqy5VJcgtZUeB7uah2zixr3YhHvLRDXWA6ib6hjGxoRb2Bd05VAzx+Iyg03QvU= X-Received: by 2002:a25:bd7:: with SMTP id 206mr4989095ybl.23.1621018217331; Fri, 14 May 2021 11:50:17 -0700 (PDT) MIME-Version: 1.0 References: <20210513175349.959661-1-surenb@google.com> In-Reply-To: From: Suren Baghdasaryan Date: Fri, 14 May 2021 11:50:06 -0700 Message-ID: Subject: Re: [PATCH 1/1] cgroup: make per-cgroup pressure stall tracking configurable To: Peter Zijlstra Cc: Tejun Heo , Johannes Weiner , lizefan.x@bytedance.com, Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Benjamin Segall , mgorman@suse.de, Minchan Kim , Jonathan Corbet , bristot@redhat.com, "Paul E . McKenney" , rdunlap@infradead.org, Andrew Morton , Thomas Gleixner , macro@orcam.me.uk, Viresh Kumar , mike.kravetz@oracle.com, linux-doc@vger.kernel.org, LKML , cgroups mailinglist , kernel-team Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Fri, May 14, 2021 at 11:20 AM Suren Baghdasaryan wrote: > > On Fri, May 14, 2021 at 10:52 AM Peter Zijlstra wrote: > > > > On Fri, May 14, 2021 at 08:54:47AM -0700, Suren Baghdasaryan wrote: > > > > > Correct, for this function CONFIG_CGROUPS=n and > > > cgroup_disable=pressure are treated the same. True, from the code it's > > > not very obvious. Do you have some refactoring in mind that would make > > > it more explicit? > > > > Does this make sense? > > > > --- a/kernel/sched/psi.c > > +++ b/kernel/sched/psi.c > > @@ -744,24 +744,26 @@ static void psi_group_change(struct psi_ > > > > static struct psi_group *iterate_groups(struct task_struct *task, void **iter) > > { > > + if (cgroup_psi_enabled()) { > > #ifdef CONFIG_CGROUPS > > - struct cgroup *cgroup = NULL; > > + struct cgroup *cgroup = NULL; > > > > - if (!*iter) > > - cgroup = task->cgroups->dfl_cgrp; > > - else if (*iter == &psi_system) > > - return NULL; > > - else > > - cgroup = cgroup_parent(*iter); > > + if (!*iter) > > + cgroup = task->cgroups->dfl_cgrp; > > + else if (*iter == &psi_system) > > + return NULL; > > + else > > + cgroup = cgroup_parent(*iter); > > > > - if (cgroup && cgroup_parent(cgroup)) { > > - *iter = cgroup; > > - return cgroup_psi(cgroup); > > - } > > -#else > > - if (*iter) > > - return NULL; > > + if (cgroup && cgroup_parent(cgroup)) { > > + *iter = cgroup; > > + return cgroup_psi(cgroup); > > + } > > #endif > > + } else { > > + if (*iter) > > + return NULL; > > + } > > *iter = &psi_system; > > return &psi_system; > > } > > Hmm. Looks like the case when cgroup_psi_enabled()==true and > CONFIG_CGROUPS=n would miss the "if (*iter) return NULL;" condition. > Effectively with CONFIG_CGROUPS=n this becomes: > > if (cgroup_psi_enabled()) { <== assume this is true > #ifdef CONFIG_CGROUPS <== compiled out > #endif > } else { > if (*iter) <== this > statement will never execute > return NULL; > } > *iter = &psi_system; > return &psi_system; > Ah, sorry. I forgot that CONFIG_CGROUPS=n would force cgroup_psi_enabled()==false (the way function is defined in cgroup.h), so (CONFIG_CGROUPS=n && cgroup_psi_enabled()==true) is an invalid configuration. I think adding a comment to your suggestion would make it more clear. So your suggestion seems to work. I'll test it and include it in the next revision. Thanks! > > > > -- > > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com. > >