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 2CE08C6FD1D for ; Fri, 31 Mar 2023 01:51:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229495AbjCaBvk (ORCPT ); Thu, 30 Mar 2023 21:51:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58452 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229475AbjCaBvj (ORCPT ); Thu, 30 Mar 2023 21:51:39 -0400 Received: from mail-pj1-x102b.google.com (mail-pj1-x102b.google.com [IPv6:2607:f8b0:4864:20::102b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7D663C4; Thu, 30 Mar 2023 18:51:38 -0700 (PDT) Received: by mail-pj1-x102b.google.com with SMTP id l9-20020a17090a3f0900b0023d32684e7fso7327637pjc.1; Thu, 30 Mar 2023 18:51:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; t=1680227498; x=1682819498; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:from:to:cc:subject:date:message-id :reply-to; bh=6XM31ZrRumkictGFOXR0ExRhhRTlkDKTwiG7dCR1Fgc=; b=JBYKiS094xTcv4zZS7qtqmMLeJJI3CBby4kLAUuMziXHD4GQX8kl0rVXktvDBOeoyg kE039cqtRpT4ykTduffb4U40BvtNgW7zV0FAZz2WV0BqlSt5QYJpN8xupFHalEgYBWe2 Mcsh414OYAuBY4FJEwUvve3aBfy2EszbwJEObj//xKUmnHYc/UwK6WW03t6iLjufAyn2 ssTRNhrXIek059u92KiSZc+dkINIxwv0V3n+b0U3qPZgOYecnTJr8KDPd568UBe+Om+Y JRzenMRK0Ov48J93rRexsFGKtXgwJ4lg877M0D9vxz9Zn9cUrB6aoYizchAGUP6OU+k8 mySQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1680227498; x=1682819498; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=6XM31ZrRumkictGFOXR0ExRhhRTlkDKTwiG7dCR1Fgc=; b=Uu4kLQFVfW8/YOQHC61hjDkn8UFrpE091wKQ8D/5jl8vfA4afcDiJQwh1o007IN0Oj 13Q0/7/kLaaVqpuUlRT1yka8IblIyILK7ooQiHGSSYCIO1MjkdWFq933Phi5ABpzzpSj bbwOXUYKPkIlg/8SHIWnhOsli5l/8gavcdvm1W+BrnT+fU5lABOxHVVRsZ/JkSugUJJj iWXNYxDazy0zl9VSkW2vnLbJEr4v7Dud2BlJzqN0l4bzepWBU4cyzmPt12yhesdygC0b rJ/gt9osChXO19nNEsGrfzVXXyr0YLdgTloFFdmUEGw79PalB+20xTRttiIHKp1UX8I6 dGcw== X-Gm-Message-State: AO0yUKWB8Ii21XFQ7+0jCC+/PAJCJ0uDtPzEUm3eZLkDDo+ag5E9uSxk za1SquZxFXX1L6kEPBJe8K8= X-Google-Smtp-Source: AK7set+UsxaaL85PLpysrGl07KRn5Za7qkDJ8HMzgvL3jq6cxWJYGFqxj4m0ugsbcUIAh+0HWFj1QQ== X-Received: by 2002:a05:6a20:b291:b0:ce:ca9:ab56 with SMTP id ei17-20020a056a20b29100b000ce0ca9ab56mr23322786pzb.34.1680227497775; Thu, 30 Mar 2023 18:51:37 -0700 (PDT) Received: from localhost (2603-800c-1a02-1bae-a7fa-157f-969a-4cde.res6.spectrum.com. [2603:800c:1a02:1bae:a7fa:157f:969a:4cde]) by smtp.gmail.com with ESMTPSA id i17-20020aa787d1000000b00627ed4e23e0sm497016pfo.101.2023.03.30.18.51.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Mar 2023 18:51:37 -0700 (PDT) Sender: Tejun Heo Date: Thu, 30 Mar 2023 15:51:35 -1000 From: Tejun Heo To: Hugh Dickins Cc: Yosry Ahmed , Shakeel Butt , Josef Bacik , Jens Axboe , Zefan Li , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Andrew Morton , Vasily Averin , cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org Subject: Re: [RFC PATCH 1/7] cgroup: rstat: only disable interrupts for the percpu lock Message-ID: References: <98cb3ce-7ed9-3d17-9015-ef7193d6627@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <98cb3ce-7ed9-3d17-9015-ef7193d6627@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Hello, Hugh. On Wed, Mar 29, 2023 at 01:38:48PM -0700, Hugh Dickins wrote: > > So, in general, there's a trade off between local irq service latency and > > inducing global lock contention when using unprotected locks. With more and > > more CPUs, the balance keeps shifting. The balance still very much depends > > on the specifics of a given lock but yeah I think it's something we need to > > be a lot more careful about now. > > And this looks a very plausible argument to me: I'll let it sink in. Another somewhat relevant change is that flipping irq on/off used to be relatively expensive on older x86 cpus. I forget all details about when and how much but they should be a lot cheaper now. No idea about !x86 cpus tho. > But I hadn't heard that the RT folks were clamouring for more irq disabling: > perhaps they partition their machines with more care, and are not devotees > of high CPU counts. I think RT folks care a lot more about raw IRQ disables. These shouldn't actually disable IRQs on RT kernels. Thanks. -- tejun