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=-17.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 4D6C5C433E0 for ; Wed, 27 Jan 2021 12:25:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0C9C420739 for ; Wed, 27 Jan 2021 12:25:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235925AbhA0MZQ (ORCPT ); Wed, 27 Jan 2021 07:25:16 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:39225 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237853AbhA0MWC (ORCPT ); Wed, 27 Jan 2021 07:22:02 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1611750036; 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=wb6zepnLUfjQE6SpoSSqkOZ1CmRA5GSq31+ma+nKIb4=; b=jHCQgeIuRqn2K+3glkqj1DxidQExzuybhv7RwPkXzU43bcXTMu4Md7fF6eXqjakX4DbcpI 7tqfyrz9itbvMOO1W9MjU583TZ3aWHT3hQv2soZLYuQmVPLnySNNYaljhO51FT5Vb/0FUR oLuhqenI5+wxvrxxWmxVmsI+XPCmmSM= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-254-vUkMZCK3Mtq2CtLoziprjg-1; Wed, 27 Jan 2021 07:20:32 -0500 X-MC-Unique: vUkMZCK3Mtq2CtLoziprjg-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D7857107ACF6; Wed, 27 Jan 2021 12:20:29 +0000 (UTC) Received: from fuller.cnet (ovpn-112-2.gru2.redhat.com [10.97.112.2]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 655285C1C2; Wed, 27 Jan 2021 12:20:22 +0000 (UTC) Received: by fuller.cnet (Postfix, from userid 1000) id 8958B4178900; Wed, 27 Jan 2021 09:19:39 -0300 (-03) Date: Wed, 27 Jan 2021 09:19:39 -0300 From: Marcelo Tosatti To: Robin Murphy Cc: Nitesh Narayan Lal , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, frederic@kernel.org, juri.lelli@redhat.com, abelits@marvell.com, bhelgaas@google.com, linux-pci@vger.kernel.org, rostedt@goodmis.org, mingo@kernel.org, peterz@infradead.org, tglx@linutronix.de, davem@davemloft.net, akpm@linux-foundation.org, sfr@canb.auug.org.au, stephen@networkplumber.org, rppt@linux.vnet.ibm.com, jinyuqi@huawei.com, zhangshaokun@hisilicon.com Subject: Re: [Patch v4 1/3] lib: Restrict cpumask_local_spread to houskeeping CPUs Message-ID: <20210127121939.GA54725@fuller.cnet> References: <20200625223443.2684-1-nitesh@redhat.com> <20200625223443.2684-2-nitesh@redhat.com> <3e9ce666-c9cd-391b-52b6-3471fe2be2e6@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3e9ce666-c9cd-391b-52b6-3471fe2be2e6@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Wed, Jan 27, 2021 at 11:57:16AM +0000, Robin Murphy wrote: > Hi, > > On 2020-06-25 23:34, Nitesh Narayan Lal wrote: > > From: Alex Belits > > > > The current implementation of cpumask_local_spread() does not respect the > > isolated CPUs, i.e., even if a CPU has been isolated for Real-Time task, > > it will return it to the caller for pinning of its IRQ threads. Having > > these unwanted IRQ threads on an isolated CPU adds up to a latency > > overhead. > > > > Restrict the CPUs that are returned for spreading IRQs only to the > > available housekeeping CPUs. > > > > Signed-off-by: Alex Belits > > Signed-off-by: Nitesh Narayan Lal > > --- > > lib/cpumask.c | 16 +++++++++++----- > > 1 file changed, 11 insertions(+), 5 deletions(-) > > > > diff --git a/lib/cpumask.c b/lib/cpumask.c > > index fb22fb266f93..85da6ab4fbb5 100644 > > --- a/lib/cpumask.c > > +++ b/lib/cpumask.c > > @@ -6,6 +6,7 @@ > > #include > > #include > > #include > > +#include > > /** > > * cpumask_next - get the next cpu in a cpumask > > @@ -205,22 +206,27 @@ void __init free_bootmem_cpumask_var(cpumask_var_t mask) > > */ > > unsigned int cpumask_local_spread(unsigned int i, int node) > > { > > - int cpu; > > + int cpu, hk_flags; > > + const struct cpumask *mask; > > + hk_flags = HK_FLAG_DOMAIN | HK_FLAG_MANAGED_IRQ; > > + mask = housekeeping_cpumask(hk_flags); > > AFAICS, this generally resolves to something based on cpu_possible_mask > rather than cpu_online_mask as before, so could now potentially return an > offline CPU. Was that an intentional change? Robin, AFAICS online CPUs should be filtered. > I was just looking at the current code since I had the rare presence of mind > to check if something suitable already existed before I start open-coding > "any online CPU, but local node preferred" logic for handling IRQ affinity > in a driver - cpumask_local_spread() appears to be almost what I want (if a > bit more heavyweight), if only it would actually guarantee an online CPU as > the kerneldoc claims :( > > Robin. > > > /* Wrap: we always want a cpu. */ > > - i %= num_online_cpus(); > > + i %= cpumask_weight(mask); > > if (node == NUMA_NO_NODE) { > > - for_each_cpu(cpu, cpu_online_mask) > > + for_each_cpu(cpu, mask) { > > if (i-- == 0) > > return cpu; > > + } > > } else { > > /* NUMA first. */ > > - for_each_cpu_and(cpu, cpumask_of_node(node), cpu_online_mask) > > + for_each_cpu_and(cpu, cpumask_of_node(node), mask) { > > if (i-- == 0) > > return cpu; > > + } > > - for_each_cpu(cpu, cpu_online_mask) { > > + for_each_cpu(cpu, mask) { > > /* Skip NUMA nodes, done above. */ > > if (cpumask_test_cpu(cpu, cpumask_of_node(node))) > > continue; > >