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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id EA013C7619A for ; Fri, 31 Mar 2023 01:51:41 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6B9DD6B0071; Thu, 30 Mar 2023 21:51:41 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 66A206B0072; Thu, 30 Mar 2023 21:51:41 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 50B9A6B0074; Thu, 30 Mar 2023 21:51:41 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 3E0AF6B0071 for ; Thu, 30 Mar 2023 21:51:41 -0400 (EDT) Received: from smtpin19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 11EDC802CD for ; Fri, 31 Mar 2023 01:51:41 +0000 (UTC) X-FDA: 80627516802.19.628CBE5 Received: from mail-pj1-f51.google.com (mail-pj1-f51.google.com [209.85.216.51]) by imf27.hostedemail.com (Postfix) with ESMTP id 2C1DF40010 for ; Fri, 31 Mar 2023 01:51:38 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=JBYKiS09; spf=pass (imf27.hostedemail.com: domain of htejun@gmail.com designates 209.85.216.51 as permitted sender) smtp.mailfrom=htejun@gmail.com; dmarc=fail reason="SPF not aligned (relaxed), DKIM not aligned (relaxed)" header.from=kernel.org (policy=none) ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1680227499; h=from:from:sender:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=6XM31ZrRumkictGFOXR0ExRhhRTlkDKTwiG7dCR1Fgc=; b=gDmtGo9//LkxpYI/SJ75t1neMcSskomkvH5y6CdwcqvoO7/0izFNzCFx2cFiNTIvLtaORB vPJWUf66FIvYaF4N/jsuo6nHgdHLesgDcPPlItSMP+zr2EAlyRi1l+tm5zjBGqS/Kuas+b 2/Sn2zhkU78MnbitSsbIgqehGLOubqI= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=JBYKiS09; spf=pass (imf27.hostedemail.com: domain of htejun@gmail.com designates 209.85.216.51 as permitted sender) smtp.mailfrom=htejun@gmail.com; dmarc=fail reason="SPF not aligned (relaxed), DKIM not aligned (relaxed)" header.from=kernel.org (policy=none) ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1680227499; a=rsa-sha256; cv=none; b=WHacoEg61dXtNqk+olL28yn2waYE00xtnUZrmkElNX+7MqyUpNtqb6aRsvXUJoVgm2rBl6 SrmNjgrBhL5W9IPDenn+OqEDrSY9NXPKj4LJ3cWKCpNnUkYDAuyzB4C+0esdiMbJaHL91V Hifb04AaLiPw4QpRly1ldip3AAKgRfw= Received: by mail-pj1-f51.google.com with SMTP id p13-20020a17090a284d00b0023d2e945aebso7607352pjf.0 for ; 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=3KhIdN3deuBrJhROv52MXDi80u1C2pHCBmkjtvsYFp0VKSDthbb9vetWxCuT+MaE8O nSh6D79M8dIqBkzDkhLfB2DfDqhrrWGZBrWwj97X36LqPgzXXESZu3EFnU7WYkzdkj5U YcQf2kIbIXS6Ptjjwza3EP4G9z+9HmeSv+/g9i/W4+raartPao+lXtLyvYTRHDbT9qos DZl57LJCVOLoNrsGGjn4T8R42Mjyyk2ikvCZb4t8narI1X6NQGJfas/bpW7J/YyKgLnY +fw7TDOK0XJ2PVZ4TwlpBRekjqV4lxc74HMSsGfkwApYU3SQi2XEtoOwvktaQzv51W7G xHKw== X-Gm-Message-State: AO0yUKUuF++1LGSHV+QRwSO+9l6JfLt7A7VoGWzXNh7AQOgbxGBW4bHa 8hQGGxfn0ZlfK29jIFIwG6w= 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) 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> X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: snwa1d8cmzas84t4bip1id5mx4rer7tm X-Rspamd-Queue-Id: 2C1DF40010 X-HE-Tag: 1680227498-308925 X-HE-Meta: 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 U6izkjrQ mN9NViEjTx7Lt2ib2LQIlu/NitR3CaBh7RGt+jbzPX1LlX+mx/FMTMnS0bbpdg4eUkrgSvVfeWyuD02xGY0NQw8aIEW7IQw7A3sHWF3Kxyjq6g08fXaZ2JiEAfnZoAdgspoucaErfgm3b0siAHkj77KdfMvwnnUw9MXJtiKy4EAF7EF/iIc74KdS4sAtARWI1a8Es93c8cK+HjN5uQquRVxvBrqL3VRU3PreWtkaKjLdO5IaX0usNe5ItzEwDwHnIkXDbcRBRKbWt1c1C98epXOF4e9Y6PypxmCiH8pCQHsiCEU7e4ZjoOyzevrxLw0sd9E8uhKUmNL61c+Iost9jdM3468YphWYOkd8ULRxtY17mXhw6Bl/lG0BwMQ+skSzGeCvKff1RtvDKJAZZ/8gvP8lg+vnBdfMBjyCH+rgqHKeBnl41Bu9qL3HZR05pJt7UonKJJoEuKaxB4OM3AruT3hBHMYrNBiI2A9INDHg9+sjjLhHlUrUnmktf5Q== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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