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 946B2EB64DC for ; Tue, 11 Jul 2023 11:42:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229591AbjGKLmb (ORCPT ); Tue, 11 Jul 2023 07:42:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59522 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230204AbjGKLm1 (ORCPT ); Tue, 11 Jul 2023 07:42:27 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1C20B1A3 for ; Tue, 11 Jul 2023 04:42:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=L73mcy0Md2qNt/m5THUnP4reYmzK9kp8si4mB9+1g1M=; b=kK50fljVE/YG+D1BO+YSkNPLG9 rrrQ2QFDf5X/HZvVpGkAqDblIT8Wf3us5T+ip+4L5N8sgJEgYYR0yn1wr7LJojNe1IZ1+pnJ/aE+b SPkwqaw0wOlPo5wGyt6JS5I7qWAGks7fvUXfYAhntDWXNiODRP4cpTM36MpkYi4JRcop88kbbwfkw HxqeLz/qCkDahhUB0Y4AA42qsTANkb6utzNSrqFZ7Llfw+38jDui+wfG2XtcSlf4ndvq2jEsIwOC1 QOcnHgna41F3hwzNp2ysJhEow/pCWH7ha4hsGiu6ZycDL149C4y4IRAD3hiDbCKRYNxXT4M0VLmFm WJ6E23fQ==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1qJBku-002NuK-2q; Tue, 11 Jul 2023 11:42:09 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 2091030036B; Tue, 11 Jul 2023 13:42:08 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 08DBF240EBDA8; Tue, 11 Jul 2023 13:42:08 +0200 (CEST) Date: Tue, 11 Jul 2023 13:42:07 +0200 From: Peter Zijlstra To: David Vernet Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, gautham.shenoy@amd.com, kprateek.nayak@amd.com, aaron.lu@intel.com, clm@meta.com, tj@kernel.org, roman.gushchin@linux.dev, kernel-team@meta.com Subject: Re: [PATCH v2 0/7] sched: Implement shared runqueue in CFS Message-ID: <20230711114207.GK3062772@hirez.programming.kicks-ass.net> References: <20230710200342.358255-1-void@manifault.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230710200342.358255-1-void@manifault.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 10, 2023 at 03:03:35PM -0500, David Vernet wrote: > Difference between shared_runq and SIS_NODE > =========================================== > > In [0] Peter proposed a patch that addresses Tejun's observations that > when workqueues are targeted towards a specific LLC on his Zen2 machine > with small CCXs, that there would be significant idle time due to > select_idle_sibling() not considering anything outside of the current > LLC. > > This patch (SIS_NODE) is essentially the complement to the proposal > here. SID_NODE causes waking tasks to look for idle cores in neighboring > LLCs on the same die, whereas shared_runq causes cores about to go idle > to look for enqueued tasks. That said, in its current form, the two > features at are a different scope as SIS_NODE searches for idle cores > between LLCs, while shared_runq enqueues tasks within a single LLC. > > The patch was since removed in [1], and we compared the results to > shared_runq (previously called "swqueue") in [2]. SIS_NODE did not > outperform shared_runq on any of the benchmarks, so we elect to not > compare against it again for this v2 patch set. Right, so SIS is search-idle-on-wakeup, while you do search-task-on-newidle, and they are indeed complentary actions. As to SIS_NODE, I really want that to happen, but we need a little more work for the Epyc things, they have a few too many CCXs per node :-) Anyway, the same thing that moticated SIS_NODE should also be relevant here, those Zen2 things have only 3/4 cores per LLC, would it not also make sense to include multiple of them into the shared runqueue thing? (My brain is still processing the shared_runq name...)