From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f200.google.com (mail-qt0-f200.google.com [209.85.216.200]) by kanga.kvack.org (Postfix) with ESMTP id 5ACA86B000E for ; Wed, 8 Aug 2018 12:30:24 -0400 (EDT) Received: by mail-qt0-f200.google.com with SMTP id b8-v6so2163611qto.16 for ; Wed, 08 Aug 2018 09:30:24 -0700 (PDT) Received: from EUR04-VI1-obe.outbound.protection.outlook.com (mail-eopbgr80122.outbound.protection.outlook.com. [40.107.8.122]) by mx.google.com with ESMTPS id s66-v6si4530772qkb.305.2018.08.08.09.30.23 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 08 Aug 2018 09:30:23 -0700 (PDT) Subject: Re: [PATCH RFC 01/10] rcu: Make CONFIG_SRCU unconditionally enabled From: Kirill Tkhai References: <153365347929.19074.12509495712735843805.stgit@localhost.localdomain> <153365625652.19074.8434946780002619802.stgit@localhost.localdomain> <20180808072040.GC27972@dhcp22.suse.cz> <20180808161330.GA22863@localhost> Message-ID: Date: Wed, 8 Aug 2018 19:30:13 +0300 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Josh Triplett Cc: Michal Hocko , akpm@linux-foundation.org, gregkh@linuxfoundation.org, rafael@kernel.org, viro@zeniv.linux.org.uk, darrick.wong@oracle.com, paulmck@linux.vnet.ibm.com, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, hughd@google.com, shuah@kernel.org, robh@kernel.org, ulf.hansson@linaro.org, aspriel@gmail.com, vivek.gautam@codeaurora.org, robin.murphy@arm.com, joe@perches.com, heikki.krogerus@linux.intel.com, sfr@canb.auug.org.au, vdavydov.dev@gmail.com, chris@chris-wilson.co.uk, penguin-kernel@I-love.SAKURA.ne.jp, aryabinin@virtuozzo.com, willy@infradead.org, ying.huang@intel.com, shakeelb@google.com, jbacik@fb.com, mingo@kernel.org, mhiramat@kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org On 08.08.2018 19:23, Kirill Tkhai wrote: > On 08.08.2018 19:13, Josh Triplett wrote: >> On Wed, Aug 08, 2018 at 01:17:44PM +0300, Kirill Tkhai wrote: >>> On 08.08.2018 10:20, Michal Hocko wrote: >>>> On Tue 07-08-18 18:37:36, Kirill Tkhai wrote: >>>>> This patch kills all CONFIG_SRCU defines and >>>>> the code under !CONFIG_SRCU. >>>> >>>> The last time somebody tried to do this there was a pushback due to >>>> kernel tinyfication. So this should really give some numbers about the >>>> code size increase. Also why can't we make this depend on MMU. Is >>>> anybody else than the reclaim asking for unconditional SRCU usage? >>> >>> I don't know one. The size numbers (sparc64) are: >>> >>> $ size image.srcu.disabled >>> text data bss dec hex filename >>> 5117546 8030506 1968104 15116156 e6a77c image.srcu.disabled >>> $ size image.srcu.enabled >>> text data bss dec hex filename >>> 5126175 8064346 1968104 15158625 e74d61 image.srcu.enabled >>> The difference is: 15158625-15116156 = 42469 ~41Kb >> >> 41k is a *substantial* size increase. However, can you compare >> tinyconfig with and without this patch? That may have a smaller change. > > $ size image.srcu.disabled > text data bss dec hex filename > 1105900 195456 63232 1364588 14d26c image.srcu.disabled > > $ size image.srcu.enabled > text data bss dec hex filename > 1106960 195528 63232 1365720 14d6d8 image.srcu.enabled > > 1365720-1364588 = 1132 ~ 1Kb 1Kb is not huge size. It looks as not a big price for writing generic code for only case (now some places have CONFIG_SRCU and !CONFIG_SRCU variants, e.g. drivers/base/core.c). What do you think?