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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 CE607C433DB for ; Tue, 9 Feb 2021 12:57:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7B94564D9D for ; Tue, 9 Feb 2021 12:57:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230229AbhBIM5G (ORCPT ); Tue, 9 Feb 2021 07:57:06 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49644 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229745AbhBIM5D (ORCPT ); Tue, 9 Feb 2021 07:57:03 -0500 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D09A9C061786 for ; Tue, 9 Feb 2021 04:56:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; 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=qMo2zzG12R0jprXXUVbuB3AdsfkG8WclBYk1eMYjOHg=; b=cYQeruhV1G3HXBPsODeVEnF9O6 6/1H7jrbyLdd0LbkyiWluwK3vBui0b3Pk8jTdjtJS5Lpl0p49bTIm+hLBsTgga/ktzFZvZ9QqXtf/ hRJbYvFjDZD4vOQRobHuf3eyr3RjESRBbPHn0oU/BJhxrLzBbPHDGum8BXzMi/II9AMd56+fijwSw XpXsuW8MmDQIhFVn3dkmdT57e6a+QRXdY6AWspJM2VyWNa8eMHGXqMKaf3ESDLzS5xeGsSKIBGsRA QZCqtHTuCVC43a0mvVjRW3KJ0up2uTh/7iicmzW4SUDheM5gAqopRjlcT4yqPy3HMh3LjNrj0xc04 ofuhoS/A==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1l9SYZ-0003kU-Dp; Tue, 09 Feb 2021 12:55:51 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id F21B6301324; Tue, 9 Feb 2021 13:55:48 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id BA2BA20568EA3; Tue, 9 Feb 2021 13:55:48 +0100 (CET) Date: Tue, 9 Feb 2021 13:55:48 +0100 From: Peter Zijlstra To: Barry Song Cc: valentin.schneider@arm.com, vincent.guittot@linaro.org, mgorman@suse.de, mingo@kernel.org, dietmar.eggemann@arm.com, morten.rasmussen@arm.com, linux-kernel@vger.kernel.org, linuxarm@openeuler.org, xuwei5@huawei.com, liguozhu@hisilicon.com, tiantao6@hisilicon.com, wanghuiqiang@huawei.com, prime.zeng@hisilicon.com, jonathan.cameron@huawei.com, guodong.xu@linaro.org, Meelis Roos Subject: Re: [PATCH v2] sched/topology: fix the issue groups don't span domain->span for NUMA diameter > 2 Message-ID: References: <20210203111201.20720-1-song.bao.hua@hisilicon.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210203111201.20720-1-song.bao.hua@hisilicon.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 04, 2021 at 12:12:01AM +1300, Barry Song wrote: > As long as NUMA diameter > 2, building sched_domain by sibling's child > domain will definitely create a sched_domain with sched_group which will > span out of the sched_domain: > > +------+ +------+ +-------+ +------+ > | node | 12 |node | 20 | node | 12 |node | > | 0 +---------+1 +--------+ 2 +-------+3 | > +------+ +------+ +-------+ +------+ > > domain0 node0 node1 node2 node3 > > domain1 node0+1 node0+1 node2+3 node2+3 > + > domain2 node0+1+2 | > group: node0+1 | > group:node2+3 <-------------------+ > > when node2 is added into the domain2 of node0, kernel is using the child > domain of node2's domain2, which is domain1(node2+3). Node 3 is outside > the span of the domain including node0+1+2. > > This will make load_balance() run based on screwed avg_load and group_type > in the sched_group spanning out of the sched_domain, and it also makes > select_task_rq_fair() pick an idle CPU out of the sched_domain. > > Real servers which suffer from this problem include Kunpeng920 and 8-node > Sun Fire X4600-M2, at least. > > Here we move to use the *child* domain of the *child* domain of node2's > domain2 as the new added sched_group. At the same time, we re-use the > lower level sgc directly. > > +------+ +------+ +-------+ +------+ > | node | 12 |node | 20 | node | 12 |node | > | 0 +---------+1 +--------+ 2 +-------+3 | > +------+ +------+ +-------+ +------+ > > domain0 node0 node1 +- node2 node3 > | > domain1 node0+1 node0+1 | node2+3 node2+3 > | > domain2 node0+1+2 | > group: node0+1 | > group:node2 <-------------------+ > I've finally had a moment to think about this, would it make sense to also break up group: node0+1, such that we then end up with 3 groups of equal size? > w/ patch, we don't get "groups don't span domain->span" any more: > [ 1.486271] CPU0 attaching sched-domain(s): > [ 1.486820] domain-0: span=0-1 level=MC > [ 1.500924] groups: 0:{ span=0 cap=980 }, 1:{ span=1 cap=994 } > [ 1.515717] domain-1: span=0-3 level=NUMA > [ 1.515903] groups: 0:{ span=0-1 cap=1974 }, 2:{ span=2-3 cap=1989 } > [ 1.516989] domain-2: span=0-5 level=NUMA > [ 1.517124] groups: 0:{ span=0-3 cap=3963 }, 4:{ span=4-5 cap=1949 } groups: 0:{ span=0-1 cap=1974 }, 2:{ span=2-3, cap=1989 }, 4:{ span=4-5, cap=1949 } > [ 1.517369] domain-3: span=0-7 level=NUMA > [ 1.517423] groups: 0:{ span=0-5 mask=0-1 cap=5912 }, 6:{ span=4-7 mask=6-7 cap=4054 } Let me continue to think about this... it's been a while :/