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 D3325C4332F for ; Wed, 14 Dec 2022 00:24:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237328AbiLNAY5 (ORCPT ); Tue, 13 Dec 2022 19:24:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49762 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236780AbiLNAYx (ORCPT ); Tue, 13 Dec 2022 19:24:53 -0500 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A5B1EB1C1; Tue, 13 Dec 2022 16:24:52 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1670977492; x=1702513492; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=BLlZbzmH6uKjXZKh08qdpfS+kNsRZLagHkkibALfGyw=; b=TqrHchrU3qe9u0L4dS+RC6jYUM/sze7vQrXMsumMwZby8EpmThFzPanx 5Zwj5f9TF3eBCZXl8nocL6uPaGSbiCqm6wARwe5f+6CNGEWG3jgwj2fLf 3715nXtSO/LvSBHAgQPBoUSiBEO2X4R09VONegEFwjBUiY/8p0zbdvG8B MBWXXIEI6Axzu2J7yfnGUfOOoC1SqEqE1kw4jybauJwdmnRwgYVv4+kl6 aBWSSVyXBfpfgyXhz4H9NEWwMWINpSXXl1BepGtpUIOv6m9I+ocTGzVmQ 2plF6SVf2Kdh4iGljkPX7oqmPmj2Xu6gmxduduUrLvHAAwR7xzP4qqLUe Q==; X-IronPort-AV: E=McAfee;i="6500,9779,10560"; a="298619820" X-IronPort-AV: E=Sophos;i="5.96,242,1665471600"; d="scan'208";a="298619820" Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Dec 2022 16:24:32 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6500,9779,10560"; a="977619192" X-IronPort-AV: E=Sophos;i="5.96,242,1665471600"; d="scan'208";a="977619192" Received: from ranerica-svr.sc.intel.com ([172.25.110.23]) by fmsmga005.fm.intel.com with ESMTP; 13 Dec 2022 16:24:32 -0800 Date: Tue, 13 Dec 2022 16:32:43 -0800 From: Ricardo Neri To: Ionela Voinescu Cc: "Peter Zijlstra (Intel)" , Juri Lelli , Vincent Guittot , Ricardo Neri , "Ravi V. Shankar" , Ben Segall , Daniel Bristot de Oliveira , Dietmar Eggemann , Len Brown , Mel Gorman , "Rafael J. Wysocki" , Srinivas Pandruvada , Steven Rostedt , Tim Chen , Valentin Schneider , x86@kernel.org, "Joel Fernandes (Google)" , linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, "Tim C . Chen" Subject: Re: [PATCH v2 09/22] sched/fair: Use IPC class score to select a busiest runqueue Message-ID: <20221214003243.GC30234@ranerica-svr.sc.intel.com> References: <20221128132100.30253-1-ricardo.neri-calderon@linux.intel.com> <20221128132100.30253-10-ricardo.neri-calderon@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 08, 2022 at 08:51:03AM +0000, Ionela Voinescu wrote: > Hi, > > On Monday 28 Nov 2022 at 05:20:47 (-0800), Ricardo Neri wrote: > > For two runqueues of equal priority and equal number of running of tasks, > > select the one whose current task would have the highest IPC class score > > if placed on the destination CPU. > > > [..] > > +static int ipcc_score_delta(struct task_struct *p, int alt_cpu) > > +{ > > + unsigned long ipcc = p->ipcc; > > + > > + if (!sched_ipcc_enabled()) > > + return INT_MIN; > > + > > + return arch_get_ipcc_score(ipcc, alt_cpu) - > > + arch_get_ipcc_score(ipcc, task_cpu(p)); > > Nit: arch_get_ipcc_score() return values are never checked for error. Fair point. I will handle error values. > > > +} > > + > > #else /* CONFIG_IPC_CLASSES */ > > static void update_sg_lb_ipcc_stats(struct sg_lb_ipcc_stats *sgcs, > > struct rq *rq) > > @@ -9258,6 +9276,11 @@ static bool sched_asym_ipcc_pick(struct sched_group *a, > > return false; > > } > > > > +static int ipcc_score_delta(struct task_struct *p, int alt_cpu) > > +{ > > + return INT_MIN; > > +} > > + > > #endif /* CONFIG_IPC_CLASSES */ > > > > /** > > @@ -10419,8 +10442,8 @@ static struct rq *find_busiest_queue(struct lb_env *env, > > { > > struct rq *busiest = NULL, *rq; > > unsigned long busiest_util = 0, busiest_load = 0, busiest_capacity = 1; > > + int i, busiest_ipcc_delta = INT_MIN; > > unsigned int busiest_nr = 0; > > - int i; > > > > for_each_cpu_and(i, sched_group_span(group), env->cpus) { > > unsigned long capacity, load, util; > > @@ -10526,8 +10549,37 @@ static struct rq *find_busiest_queue(struct lb_env *env, > > > > case migrate_task: > > if (busiest_nr < nr_running) { > > + struct task_struct *curr; > > + > > busiest_nr = nr_running; > > busiest = rq; > > + > > + /* > > + * Remember the IPC score delta of busiest::curr. > > + * We may need it to break a tie with other queues > > + * with equal nr_running. > > + */ > > + curr = rcu_dereference(busiest->curr); > > + busiest_ipcc_delta = ipcc_score_delta(curr, > > + env->dst_cpu); > > + /* > > + * If rq and busiest have the same number of running > > + * tasks, pick rq if doing so would give rq::curr a > > + * bigger IPC boost on dst_cpu. > > + */ > > + } else if (sched_ipcc_enabled() && > > + busiest_nr == nr_running) { > > + struct task_struct *curr; > > + int delta; > > + > > + curr = rcu_dereference(rq->curr); > > + delta = ipcc_score_delta(curr, env->dst_cpu); > > + > > + if (busiest_ipcc_delta < delta) { > > + busiest_ipcc_delta = delta; > > + busiest_nr = nr_running; > > + busiest = rq; > > + } > > } > > break; > > > > While in the commit message you describe this as breaking a tie for > asym_packing, Are you referring to the overall series or this specific patch? I checked commit message and I do not see references to asym_packing. > the code here does not only affect asym_packing. If > another architecture would have sched_ipcc_enabled() it would use this > as generic policy, and that might not be desired. Indeed, the patchset implements support to use IPCC classes for asym_packing, but it is not limited to it. It is true that I don't check here for asym_packing, but it should not be a problem, IMO. I compare two runqueues with equal nr_running, either runqueue is a good choice. This tie breaker is an overall improvement, no? Thanks and BR, Ricardo