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 2CEFBC4345F for ; Fri, 19 Apr 2024 10:17:04 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 44D116B0082; Fri, 19 Apr 2024 06:17:03 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3FC686B0085; Fri, 19 Apr 2024 06:17:03 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2C35A6B0087; Fri, 19 Apr 2024 06:17:03 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 0DDD66B0082 for ; Fri, 19 Apr 2024 06:17:03 -0400 (EDT) Received: from smtpin05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 972BA1C10B2 for ; Fri, 19 Apr 2024 10:17:02 +0000 (UTC) X-FDA: 82025878284.05.E7C052F Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by imf18.hostedemail.com (Postfix) with ESMTP id 9704F1C000D for ; Fri, 19 Apr 2024 10:17:00 +0000 (UTC) Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=tNIPxI5H; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf18.hostedemail.com: domain of hawk@kernel.org designates 145.40.73.55 as permitted sender) smtp.mailfrom=hawk@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1713521821; h=from:from: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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=quM63crfd1qy+ADizxnvgIVenMyXIvAEX0e83769e3g=; b=4gozK7RpHtoDibev+zhHH/7REykfscA09XzaGqjoeQ01isrnKBZzI8DsQQ671B6gtnWVJX usO8DyZwUbeT3M6Bc9NQyoAEBmRdotc3lDL0vX6tsNAmKNYZHUsBsOicmZ9FeWPRwDcaJz JRZUWJv2zwU5Qa49RSj2grahDWUdbTA= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=tNIPxI5H; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf18.hostedemail.com: domain of hawk@kernel.org designates 145.40.73.55 as permitted sender) smtp.mailfrom=hawk@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1713521821; a=rsa-sha256; cv=none; b=gcz9UsNHZESwrGkBQmCuo9ILOpTubDOEOmbBv8sLfLplGkLvA6xMP78AYb05nuUdy/smXA MgZTd8HznADDPDfFJ4lOY+Ll/SvnzQ/+ojq0C+lvJMe1b+Ku8hLDNLyMUpZbTFOhZrUwuG x61j3/MPKb71UxHeODoPNqV4QGmmLlY= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sin.source.kernel.org (Postfix) with ESMTP id 2D661CE1A46; Fri, 19 Apr 2024 10:16:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A9E1AC072AA; Fri, 19 Apr 2024 10:16:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1713521816; bh=aC+QA5rjhgsuTqn2kdyip+wg1YmdpSU1U1t0y/JyVB4=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=tNIPxI5HOVILSTXuczGUDtJGoDhmBpJGSxMEqBFvHNc2zXK33PEiKk4HM+8mTjKo/ bu1QPvghvyq31zosBe16/stXNcEqYWg5NdaCyQQ+0r0jpOYs1k0v8NDfk93oso4wyk 3jIMkkHrA7DgSmPunJ14oE0XNCHPHd0btuepG1tf77WZG83xIcjHaeL1Gzdw/tFMp1 Dau3NJVvA9W6sTlorR3yNNq/IyMUo29+AmiNyDXYRERCMv0FSe56YLuG2ErpFVxtuG o8+arByas5NQ5ha1eVk7zFPlQHUct8n2jtqpmfHIuwRBE2lZiVWcAn6bP2VSZQrscQ qR9DgG4w1BvVg== Message-ID: <33295077-e969-427a-badb-3e29698f5cfb@kernel.org> Date: Fri, 19 Apr 2024 12:16:52 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 3/3] cgroup/rstat: introduce ratelimited rstat flushing To: Yosry Ahmed Cc: tj@kernel.org, hannes@cmpxchg.org, lizefan.x@bytedance.com, cgroups@vger.kernel.org, longman@redhat.com, netdev@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, shakeel.butt@linux.dev, kernel-team@cloudflare.com, Arnaldo Carvalho de Melo , Sebastian Andrzej Siewior , mhocko@kernel.org, Wei Xu References: <171328983017.3930751.9484082608778623495.stgit@firesoul> <171328990014.3930751.10674097155895405137.stgit@firesoul> <72e4a55e-a246-4e28-9d2e-d4f1ef5637c2@kernel.org> Content-Language: en-US From: Jesper Dangaard Brouer In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 9704F1C000D X-Stat-Signature: 4w6ieumedyroyqkgownaoswuuwpqhadg X-HE-Tag: 1713521820-396960 X-HE-Meta: U2FsdGVkX18msZsHbxjTLoNuM/6SfMFePYc9UaiZFpGrdJVYdktK+atXFwnIwd4rIJ0/AfOyrVwnRoelIgi51AZUiKyIEmhsD20ttvyJbaD2m1Nepu9VraxZANsNaSs0oBofVJvb1drSusI8W6ea/dhuPOSHZhJPmVO0eulhp929NR6XIEvhz2DSZWJNN1nKfJ/Y14VEjOgYdOo4xuN5U4WKrMHfSoM0XLdqcUnBDm40L+01keuSbMb+C3K3bqZ/bfNAf5rTOBYdwA44FzjMeyv6fVwdZJ+xsnxuuPMeCDtjlsICwaOO13L78YRyFpC1SbabvahrJM3NwDtIJeHEYPIKB+y0bhLm5h9+bj1lhg5lGjOy3o5LjDaq1t/v17pbE/lY4WvX4ZxFN1egTu6Qv14akdJTbs2JpY7hHJ8gmx17kKCgcyKLXShTywykdG3rjW3/23bTWK+5wxPoJyEQx1WfLgDfuIOog6vlx335Mw0T7DTchvWqt2keLwmVNcMNTgbu/0wMjS7e0qEMd/3/g8ps+SWmYPT+6ILqmGjavpv5gkFJZIeRTUxPNWqtT7JBs77Rr6CJc8QDRiIFy1O3qQN+J7/yVWBkM7JORrKwIzQ+tXsUqwicxEMaiamG0jz3b/C/tlXBtLalrW3FbTOswuZekaOYryZgm+Hw+a3MtvfRNgpvsyEemNpsEHd4yX/8EH4Z26kdgWWeX7tnpRKi6Sjs/I6ioWCnGkhnN4gXDybHRDsvJ7708yKhL+3OXZETkwmrPu20dOqAqnK0WwpCZU/WAc2+Wl9Lghzyow9zLuJ/Nl9XHaivDUHKWZ+BCPhsHOKf4avWUJQ0dzjdkJMgv5kJ3/AzXV0uJx86FKUy095Id+RmR6brI4A9H7eEQ/97kH0o77FUythV08c7Hd3mZWk5FXqJS8w1lqEEJjAvIvj/N1/xWJ5ABQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000519, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 18/04/2024 23.00, Yosry Ahmed wrote: > On Thu, Apr 18, 2024 at 4:00 AM Jesper Dangaard Brouer wrote: >> On 18/04/2024 04.21, Yosry Ahmed wrote: >>> On Tue, Apr 16, 2024 at 10:51 AM Jesper Dangaard Brouer wrote: >>>> This patch aims to reduce userspace-triggered pressure on the global >>>> cgroup_rstat_lock by introducing a mechanism to limit how often reading >>>> stat files causes cgroup rstat flushing. >>>> [...] > Taking a step back, I think this series is trying to address two > issues in one go: interrupt handling latency and lock contention. Yes, patch 2 and 3 are essentially independent and address two different aspects. > While both are related because reducing flushing reduces irq > disablement, I think it would be better if we can fix that issue > separately with a more fundamental solution (e.g. using a mutex or > dropping the lock at each CPU boundary). > > After that, we can more clearly evaluate the lock contention problem > with data purely about flushing latency, without taking into > consideration the irq handling problem. > > Does this make sense to you? Yes, make sense. So, you are suggesting we start with the mutex change? (patch 2) (which still needs some adjustments/tuning) This make sense to me, as there are likely many solutions to reducing the pressure on the lock. With the tracepoint patch in-place, I/we can measure the pressure on the lock, and I plan to do this across our CF fleet. Then we can slowly work on improving lock contention and evaluate this on our fleets. --Jesper p.s. Setting expectations: - Going on vacation today, so will resume work after 29th April.