From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f198.google.com (mail-qk0-f198.google.com [209.85.220.198]) by kanga.kvack.org (Postfix) with ESMTP id E1E796B025F for ; Mon, 20 Nov 2017 13:28:44 -0500 (EST) Received: by mail-qk0-f198.google.com with SMTP id 78so5193657qkz.13 for ; Mon, 20 Nov 2017 10:28:44 -0800 (PST) Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com. [148.163.156.1]) by mx.google.com with ESMTPS id v23si3579432qkl.430.2017.11.20.10.28.43 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 20 Nov 2017 10:28:43 -0800 (PST) Received: from pps.filterd (m0098410.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id vAKIPX3h009905 for ; Mon, 20 Nov 2017 13:28:42 -0500 Received: from e15.ny.us.ibm.com (e15.ny.us.ibm.com [129.33.205.205]) by mx0a-001b2d01.pphosted.com with ESMTP id 2ec16qbjqv-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 20 Nov 2017 13:28:42 -0500 Received: from localhost by e15.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 20 Nov 2017 13:28:41 -0500 Date: Mon, 20 Nov 2017 10:28:38 -0800 From: "Paul E. McKenney" Subject: Re: [PATCH 1/2] mm,vmscan: Kill global shrinker lock. Reply-To: paulmck@linux.vnet.ibm.com References: <20171117173521.GA21692@infradead.org> <20171120092526.llj2q3lqbbxwn4g4@dhcp22.suse.cz> <20171120093309.GA19627@infradead.org> <20171120094237.z6h3kx3ne5ld64pl@dhcp22.suse.cz> <20171120104129.GA25042@infradead.org> <201711201956.IIB86978.OFMVFFOJLtOSHQ@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201711201956.IIB86978.OFMVFFOJLtOSHQ@I-love.SAKURA.ne.jp> Message-Id: <20171120182838.GU3624@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Tetsuo Handa Cc: hch@infradead.org, mhocko@kernel.org, minchan@kernel.org, ying.huang@intel.com, mgorman@techsingularity.net, vdavydov.dev@gmail.com, hannes@cmpxchg.org, akpm@linux-foundation.org, shakeelb@google.com, gthelen@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org On Mon, Nov 20, 2017 at 07:56:28PM +0900, Tetsuo Handa wrote: > Christoph Hellwig wrote: > > On Mon, Nov 20, 2017 at 10:42:37AM +0100, Michal Hocko wrote: > > > The patch has been dropped because allnoconfig failed to compile back > > > then http://lkml.kernel.org/r/CAP=VYLr0rPWi1aeuk4w1On9CYRNmnEWwJgGtaX=wEvGaBURtrg@mail.gmail.com > > > I have problem to find the follow up discussion though. The main > > > argument was that SRC is not generally available and so the core > > > kernel should rely on it. > > > > Paul, > > > > isthere any good reason to not use SRCU in the core kernel and > > instead try to reimplement it using atomic counters? > > CONFIG_SRCU was added in order to save system size. There are users who run Linux on very > small systems ( https://www.elinux.org/images/5/52/Status-of-embedded-Linux-2017-09-JJ62.pdf ). > > Also, atomic counters are not mandatory for shrinker case; e.g. > http://lkml.kernel.org/r/201711161956.EBF57883.QFFMOLOVSOHJFt@I-love.SAKURA.ne.jp . CONFIG_SRCU was indeed added in order to shrink single-CPU systems. But many architectures are now requiring SRCU for one reason or another, in more and more situations. So I recently implemented a UP-only Tiny SRCU, which is quite a bit smaller than its scalable counterpart, Tree SRCU: text data bss dec hex filename 983 64 0 1047 417 /tmp/c/kernel/rcu/srcutiny.o text data bss dec hex filename 6844 193 0 7037 1b7d /tmp/b/kernel/rcu/srcutree.o So perhaps it is time to unconditionally enable SRCU? Thanx, Paul -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org