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 X-Spam-Level: X-Spam-Status: No, score=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 58A97C433B4 for ; Wed, 7 Apr 2021 09:50:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 18B23611C0 for ; Wed, 7 Apr 2021 09:50:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346113AbhDGJuK (ORCPT ); Wed, 7 Apr 2021 05:50:10 -0400 Received: from mx2.suse.de ([195.135.220.15]:34386 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346088AbhDGJuJ (ORCPT ); Wed, 7 Apr 2021 05:50:09 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 815FAAE06; Wed, 7 Apr 2021 09:49:59 +0000 (UTC) To: Zheng Yongjun Cc: Hulk Robot , kent.overstreet@gmail.com, linux-kernel@vger.kernel.org, linux-bcache@vger.kernel.org References: <20210407093848.567720-1-zhengyongjun3@huawei.com> From: Coly Li Subject: Re: [PATCH -next v2] bcache: use DEFINE_MUTEX() for mutex lock Message-ID: <7037a34e-988e-dbf5-9bed-e40f5e11c36b@suse.de> Date: Wed, 7 Apr 2021 17:49:56 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.9.0 MIME-Version: 1.0 In-Reply-To: <20210407093848.567720-1-zhengyongjun3@huawei.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-bcache@vger.kernel.org On 4/7/21 5:38 PM, Zheng Yongjun wrote: > mutex lock can be initialized automatically with DEFINE_MUTEX() rather > than explicitly calling mutex_init(). > > this patch will reduce the size of bcache.ko about 64 bytes, the reason > as follows: > > though this patch will increase the size of .data segment about 32 bytes, > it will also reduce the size of .init.text and .rodata.str1.1(at x86_64), > .rodata_str1.8(at arm64) and .bss segment total about 96 bytes which reduce > the size more than .data segment; > Thanks for the following information. BTW, the bss section should be ignored, because they don't take physical file size. It seems although the patched code has larger .data section, but the generated code in .init.text and .rodata.str1.1(or 8) are much lesser than the increased size. This is really interesting :-) Your data is convinced, it is fair to take this patch in. Could you please post a v3 version which removes the .bss information ? Coly Li > here is the statistics: > Sections: (arm64 platform) > Idx name size > -.init.text 00000240 > +.init.text 00000228 > > -.rodata.str1.8 000012cd > +.rodata.str1.8 000012b5 > > -.data 00000c60 > +.data 00000c80 > > -.bss 00000080 > +.bss 00000060 > > Sections: (x86 platform) > Idx name size > -.init.text 000001d9 > +.init.text 000001bf > > -.rodata.str1.1 00000c80 > +.rodata.str1.1 00000c6d > > -.data 00000cc0 > +.data 00000ce0 > > -.bss 00000080 > +.bss 00000070 > > Reported-by: Hulk Robot > Signed-off-by: Zheng Yongjun > --- > drivers/md/bcache/super.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c > index 03e1fe4de53d..3635f454309e 100644 > --- a/drivers/md/bcache/super.c > +++ b/drivers/md/bcache/super.c > @@ -40,7 +40,7 @@ static const char invalid_uuid[] = { > }; > > static struct kobject *bcache_kobj; > -struct mutex bch_register_lock; > +DEFINE_MUTEX(bch_register_lock); > bool bcache_is_reboot; > LIST_HEAD(bch_cache_sets); > static LIST_HEAD(uncached_devices); > @@ -2869,7 +2869,6 @@ static int __init bcache_init(void) > > check_module_parameters(); > > - mutex_init(&bch_register_lock); > init_waitqueue_head(&unregister_wait); > register_reboot_notifier(&reboot); > >