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 28BFBC433FE for ; Thu, 3 Nov 2022 10:11:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230329AbiKCKLa (ORCPT ); Thu, 3 Nov 2022 06:11:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45334 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229523AbiKCKL2 (ORCPT ); Thu, 3 Nov 2022 06:11:28 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DE2F4B75 for ; Thu, 3 Nov 2022 03:11:27 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 9B0C21F890; Thu, 3 Nov 2022 10:11:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1667470286; h=from:from:reply-to: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=gIbn6Jdny57DgvpWIdnJozO9qB7X5TWdsi4aX7H7iv8=; b=ehzIkwZa+O9DsxbLL9MRsGmkXcdHWo4t7jYzAOBmeX6PnIux5PBgf85ILX4bg1qy3IKtrT e2ErdGPVKQN8waLS7HBrpRPKd4YXf1uSVnEwfMR7FupMI2m3WAiWijIF/mdeEvTKEJLiz5 r+GUPSmbetSkE+c0gwYMy0zakiWjcOA= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 60B0913AAF; Thu, 3 Nov 2022 10:11:26 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id cxyjFs6TY2MDcAAAMHmgww (envelope-from ); Thu, 03 Nov 2022 10:11:26 +0000 Date: Thu, 3 Nov 2022 11:11:24 +0100 From: Michal =?iso-8859-1?Q?Koutn=FD?= To: Josh Don Cc: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Valentin Schneider , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] sched: async unthrottling for cfs bandwidth Message-ID: <20221103101124.GD10591@blackbody.suse.cz> References: <20221026224449.214839-1-joshdon@google.com> <20221102165922.GA31833@blackbody.suse.cz> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="wULyF7TL5taEdwHz" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --wULyF7TL5taEdwHz Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, Nov 02, 2022 at 05:10:08PM -0700, Josh Don wrote: > Without my patch, distribute_cfs_runtime() will unthrottle the > cfs_rq's, and as you point out, it doesn't actually give them any real > quota, it lets assign_cfs_rq_runtime() take care of that. But this > happens asynchronously on those cpus. If they are idle, they wait for > an IPI from the resched_curr() in unthrottled_cfs_rq(), otherwise they > simply wait until potentially the next rescheduling point. So we are > currently far from ever being guaranteed that the order the cpus pull > actual quota via assign_cfs_rq_runtime() matches the order they were > unthrottled from the list. Thanks for breaking it down, I agree your change won't affect the fairness substantially and my other points are clarified too. Michal --wULyF7TL5taEdwHz Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- iHUEARYIAB0WIQTrXXag4J0QvXXBmkMkDQmsBEOquQUCY2OTugAKCRAkDQmsBEOq uR3pAQDo5+2d5zDKYrRDoKurRMR240+Jnvbif9Y21KaDfIpEKAEA5mv0PJFfF0z9 JH+NhJC7BFmoXqzJyiZ5KYTCl/YWAgg= =AKaU -----END PGP SIGNATURE----- --wULyF7TL5taEdwHz--