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 DB8F0C433EF for ; Fri, 18 Feb 2022 16:09:51 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 21E0E6B0073; Fri, 18 Feb 2022 11:09:51 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 1CE2C6B0075; Fri, 18 Feb 2022 11:09:51 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 06EF96B0078; Fri, 18 Feb 2022 11:09:51 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0166.hostedemail.com [216.40.44.166]) by kanga.kvack.org (Postfix) with ESMTP id EE30C6B0073 for ; Fri, 18 Feb 2022 11:09:50 -0500 (EST) Received: from smtpin23.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id AD425998B7 for ; Fri, 18 Feb 2022 16:09:50 +0000 (UTC) X-FDA: 79156386540.23.A8DC6F3 Received: from mail-lf1-f41.google.com (mail-lf1-f41.google.com [209.85.167.41]) by imf11.hostedemail.com (Postfix) with ESMTP id 2F0BC40007 for ; Fri, 18 Feb 2022 16:09:50 +0000 (UTC) Received: by mail-lf1-f41.google.com with SMTP id j15so6326091lfe.11 for ; Fri, 18 Feb 2022 08:09:49 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=8gUAABA3j3f1FRh38YxGuqY86VzPDifyEVw8iwRRkpw=; b=cyWkAO0iWWXZ5RX3hmvLYfEnD4qtbZcgGTUs/I4Eg1grFIrrB5/Wd595bPPNN8gV75 4uLVzqdO6mgrPtNahiDzECg+2hz2mpA/jll0Uz1e9vE3/dEfS2cHeJ7a6ELdiCq72hDx gBhiBpg+mRkGjwza4EY6K7UOBZ7+u69+V0AUR9zA02dO0T0bJB2yvtXHpZGOfELslWYp Jqzrp1aTYcHK5wKyzEHcIraox5zejrYEfvGtu64Lluf3xQcg3piCrWRqWf56z/DTi0f8 VKyGAm8RBs2yYcH8wVnBOGwrQZiC8x90T/EmeljJ9eCVe24yF5+2EKiUZuBwMHqhtcB/ TQzg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=8gUAABA3j3f1FRh38YxGuqY86VzPDifyEVw8iwRRkpw=; b=qG6K9M2SFL+FbZWZAtdqjiuGeLweqf/UTOntyonwcHAz1VTdiCVEO6Ne5Z4RQK1NIg 0LbmS3KYadn5AegpP9noWMayJeUyKgSZUcYDJK8EFYtaggSPr5uREY+desEfM38mUCwk h5nIovY1ZrX377bwZkw1SHZCzjp4uxSn9n7Fogv2QgComngMxhuZrKG6G/VxrtbngjvT 13iCET3XrhpsO9fFEql9ZigMlTWYL4YIbet8xgs2jBtiMbkzqmBR83177w9k7sBLAP9Y kfnTtxgCpySQZHCz5z3zQ/p2Zesl103RQuCFFsRbjWCPtQaOBrH+13pj3jaI8JXXSZ2g S09Q== X-Gm-Message-State: AOAM530Q9sCRs3TQaZI5EsNklGUhc7FCYDJZ48Ko1jX/5CQCJVw74bSF lkpQjidTCW+I43Q3/2kzxRIHg6k+ovDowTlTDz57KQ== X-Google-Smtp-Source: ABdhPJxC+0P6mzNCudfOUmF2+1/m+DdL2qJoJkzkh8QVFxs+1WMA6P8RW8xTZO0FEIIgGs78tI0REqWRCuF2q1wdq30= X-Received: by 2002:a05:6512:388d:b0:443:6066:2c8d with SMTP id n13-20020a056512388d00b0044360662c8dmr5730000lft.184.1645200588394; Fri, 18 Feb 2022 08:09:48 -0800 (PST) MIME-Version: 1.0 References: <20220217094802.3644569-1-bigeasy@linutronix.de> <20220217094802.3644569-2-bigeasy@linutronix.de> In-Reply-To: <20220217094802.3644569-2-bigeasy@linutronix.de> From: Shakeel Butt Date: Fri, 18 Feb 2022 08:09:36 -0800 Message-ID: Subject: Re: [PATCH v3 1/5] mm/memcg: Revert ("mm/memcg: optimize user context object stock access") To: Sebastian Andrzej Siewior Cc: Cgroups , Linux MM , Andrew Morton , Johannes Weiner , Michal Hocko , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Peter Zijlstra , Thomas Gleixner , Vladimir Davydov , Waiman Long , Michal Hocko , Roman Gushchin Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=cyWkAO0i; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf11.hostedemail.com: domain of shakeelb@google.com designates 209.85.167.41 as permitted sender) smtp.mailfrom=shakeelb@google.com X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 2F0BC40007 X-Stat-Signature: 3hma6ek5tnynpf6b33hzpo9m96dqxcoo X-HE-Tag: 1645200590-299649 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000234, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Feb 17, 2022 at 1:48 AM Sebastian Andrzej Siewior wrote: > > From: Michal Hocko > > The optimisation is based on a micro benchmark where local_irq_save() is > more expensive than a preempt_disable(). There is no evidence that it is > visible in a real-world workload and there are CPUs where the opposite is > true (local_irq_save() is cheaper than preempt_disable()). > > Based on micro benchmarks, the optimisation makes sense on PREEMPT_NONE > where preempt_disable() is optimized away. There is no improvement with > PREEMPT_DYNAMIC since the preemption counter is always available. > > The optimization makes also the PREEMPT_RT integration more complicated > since most of the assumption are not true on PREEMPT_RT. > > Revert the optimisation since it complicates the PREEMPT_RT integration > and the improvement is hardly visible. > > [ bigeasy: Patch body around Michal's diff ] > > Link: https://lore.kernel.org/all/YgOGkXXCrD%2F1k+p4@dhcp22.suse.cz > Link: https://lkml.kernel.org/r/YdX+INO9gQje6d0S@linutronix.de > Signed-off-by: Michal Hocko > Signed-off-by: Sebastian Andrzej Siewior > Acked-by: Roman Gushchin > Acked-by: Johannes Weiner Reviewed-by: Shakeel Butt