From mboxrd@z Thu Jan 1 00:00:00 1970 From: Juri Lelli Subject: Re: [RFC PATCH 0/3] sched/deadline: cpuset: Rework DEADLINE bandwidth restoration Date: Wed, 15 Mar 2023 17:10:54 +0000 Message-ID: References: <20230315121812.206079-1-juri.lelli@redhat.com> <20230315145514.vjoypwadprvpgwam@airbuntu> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1678900260; 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: in-reply-to:in-reply-to:references:references; bh=shMiUju0CLJ7Dpi4MvVas/gIt/IesSMILI0VOCkmlZA=; b=dDQ7u9b7gdCU13FJnFPiVpb5t4aA/6VnC8hi7UZSqmA3JerqqVGJaDAk1Lyvq/jyu+h2Tt Tnv6Q/TUSxh3MxZ5nx0fAruGWhLkSGb7OAL4qgWL7Toq/WwLDqJrJvJN8OHWcjYiQbRwuc LbqBigDdvkFtI2kOLIzj4wxnvVTk4Fs= Content-Disposition: inline In-Reply-To: <20230315145514.vjoypwadprvpgwam@airbuntu> List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Qais Yousef Cc: Peter Zijlstra , Ingo Molnar , Waiman Long , Tejun Heo , Zefan Li , Johannes Weiner , Hao Luo , Dietmar Eggemann , Steven Rostedt , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, luca.abeni-5rdYK369eBLQB0XuIGIEkQ@public.gmane.org, claudio-YOzL5CV4y4YG1A2ADO40+w@public.gmane.org, tommaso.cucinotta-5rdYK369eBLQB0XuIGIEkQ@public.gmane.org, bristot-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, mathieu.poirier-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Vincent Guittot , Wei Wang , Rick Yiu , Quentin Perret , Heiko Carstens , Vasily Gorbik , Alexander Gordeev On 15/03/23 14:55, Qais Yousef wrote: > On 03/15/23 12:18, Juri Lelli wrote: > > Qais reported [1] that iterating over all tasks when rebuilding root > > domains for finding out which ones are DEADLINE and need their bandwidth > > correctly restored on such root domains can be a costly operation (10+ > > ms delays on suspend-resume). He proposed we skip rebuilding root > > domains for certain operations, but that approach seemed arch specific > > and possibly prone to errors, as paths that ultimately trigger a rebuild > > might be quite convoluted (thanks Qais for spending time on this!). > > Thanks a lot for this! And sorry I couldn't provide something better. Ah, no worries. Actually still have to convice myself what I have it's actually better. :) > > > > To fix the problem I instead would propose we > > > > 1 - Bring back cpuset_mutex (so that we have write access to cpusets > > from scheduler operations - and we also fix some problems > > associated to percpu_cpuset_rwsem) > > 2 - Keep track of the number of DEADLINE tasks belonging to each cpuset > > 3 - Use this information to only perform the costly iteration if > > DEADLINE tasks are actually present in the cpuset for which a > > corresponding root domain is being rebuilt > > nit: > > Would you consider adding another patch to rename the functions? > rebuild_root_domains() and update_tasks_root_domain() are deadline accounting > specific functions and don't actually rebuild root domains. Yep, can do. Thanks, Juri