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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 2169FC433F5 for ; Sat, 11 Sep 2021 21:47:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E9A1B611AD for ; Sat, 11 Sep 2021 21:47:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231441AbhIKVsz (ORCPT ); Sat, 11 Sep 2021 17:48:55 -0400 Received: from mail-pj1-f54.google.com ([209.85.216.54]:51058 "EHLO mail-pj1-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231415AbhIKVsz (ORCPT ); Sat, 11 Sep 2021 17:48:55 -0400 Received: by mail-pj1-f54.google.com with SMTP id k23so3724767pji.0 for ; Sat, 11 Sep 2021 14:47:42 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=duU6elpbWThTuSplJOTkl7u0agKkufdEWYuSm3PD6iU=; b=S+Rah8ErYG5K33CGhdmWaA/sm1eqRh7p2mkzVDvvT2ntyw0VuD3Qmtp9OQ+T+XeUrA fpwWvXB5fISYjLT6GP5Wrr1ZUbeKFTW7xBco0DgO8XgNBjAaRDS3+5C5LuYRLH4rufiJ avF1PX+aIE82hv27jg3reHHWo/5afpR5Wo5PHoyk1qg1yHUEorIWjDQVHN87UgMhEbzT 2hi2vxpzdgYehwZyud9qASfvjGwKzzdcCcm9yswO4o1M2x/tbov86AgRcaL87j3FWZAV ePwEmdEmmwJJzFPKZ5xMNfjtDZCpEZKymDB/7WjhESjgpguqsl2glpYD0x/txnfJO1zT B34g== X-Gm-Message-State: AOAM530zNpHju8Q/iRo0G9nTK1O9gjPGcybztPum5FdyrUObws25X2L0 Z2yo+iKFUYngxfVxwAKNxxg= X-Google-Smtp-Source: ABdhPJwTQ9i0VaPluB/gHgtcNMlDBwu//uTOJOgVcH/IMXLCXQVaCNMdyhv3wEnW8m518cCzeStUXA== X-Received: by 2002:a17:902:ce84:b0:138:9422:512e with SMTP id f4-20020a170902ce8400b001389422512emr3964235plg.12.1631396861554; Sat, 11 Sep 2021 14:47:41 -0700 (PDT) Received: from asus.hsd1.ca.comcast.net ([2601:647:4000:d7:8e23:83c0:a404:a54f]) by smtp.gmail.com with ESMTPSA id d3sm2577786pjc.49.2021.09.11.14.47.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 11 Sep 2021 14:47:40 -0700 (PDT) From: Bart Van Assche To: Jens Axboe Cc: linux-block@vger.kernel.org, Christoph Hellwig , Bart Van Assche Subject: [PATCH] block: Optimize bio_init() Date: Sat, 11 Sep 2021 14:47:34 -0700 Message-Id: <20210911214734.4692-1-bvanassche@acm.org> X-Mailer: git-send-email 2.33.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org The following test: sudo taskset -c 0 t/io_uring -b512 -d128 -c32 -s32 -p1 -F1 -B1 /dev/nullb0 reports 1366 K IOPS on my test setup without this patch and 1380 K IOPS with this patch applied. In other words, this patch realizes a 1% performance improvement. I think this is because this patch makes the compiler generate better code. See also commit da521626ac62 ("bio: optimize initialization of a bio"). The assembler code generated by gcc without this patch is as follows: 0x0000000000000000 <+0>: call 0x5 0x0000000000000005 <+5>: xor %eax,%eax 0x0000000000000007 <+7>: xor %ecx,%ecx 0x0000000000000009 <+9>: movl $0x1,0x1c(%rdi) 0x0000000000000010 <+16>: movq $0x0,(%rdi) 0x0000000000000017 <+23>: movq $0x0,0x8(%rdi) 0x000000000000001f <+31>: movq $0x0,0x10(%rdi) 0x0000000000000027 <+39>: mov %ax,0x18(%rdi) 0x000000000000002b <+43>: movb $0x0,0x1a(%rdi) 0x000000000000002f <+47>: movq $0x0,0x20(%rdi) 0x0000000000000037 <+55>: movq $0x0,0x28(%rdi) 0x000000000000003f <+63>: movl $0x0,0x30(%rdi) 0x0000000000000046 <+70>: movq $0x0,0x38(%rdi) 0x000000000000004e <+78>: movq $0x0,0x40(%rdi) 0x0000000000000056 <+86>: movq $0x0,0x48(%rdi) 0x000000000000005e <+94>: movq $0x0,0x50(%rdi) 0x0000000000000066 <+102>: movq $0x0,0x58(%rdi) 0x000000000000006e <+110>: movq $0x0,0x60(%rdi) 0x0000000000000076 <+118>: mov %cx,0x68(%rdi) 0x000000000000007a <+122>: movl $0x1,0x6c(%rdi) 0x0000000000000081 <+129>: mov %dx,0x6a(%rdi) 0x0000000000000085 <+133>: mov %rsi,0x70(%rdi) 0x0000000000000089 <+137>: movq $0x0,0x78(%rdi) 0x0000000000000091 <+145>: ret With this patch bio_init() is compiled into the following assembly code: 0x0000000000000000 <+0>: call 0x5 0x0000000000000005 <+5>: mov %rdi,%r8 0x0000000000000008 <+8>: mov $0x10,%ecx 0x000000000000000d <+13>: xor %eax,%eax 0x000000000000000f <+15>: rep stos %rax,%es:(%rdi) 0x0000000000000012 <+18>: movl $0x1,0x1c(%r8) 0x000000000000001a <+26>: mov %dx,0x6a(%r8) 0x000000000000001f <+31>: movl $0x1,0x6c(%r8) 0x0000000000000027 <+39>: mov %rsi,0x70(%r8) 0x000000000000002b <+43>: ret Cc: Christoph Hellwig Signed-off-by: Bart Van Assche --- block/bio.c | 45 ++++++++------------------------------------- 1 file changed, 8 insertions(+), 37 deletions(-) diff --git a/block/bio.c b/block/bio.c index 5df3dd282e40..775cd4274523 100644 --- a/block/bio.c +++ b/block/bio.c @@ -244,47 +244,18 @@ static void bio_free(struct bio *bio) } /* - * Users of this function have their own bio allocation. Subsequently, - * they must remember to pair any call to bio_init() with bio_uninit() - * when IO has completed, or when the bio is released. + * Users of this function must pair any call to bio_init() with a call to + * bio_uninit() after IO has completed or when the bio is released. */ void bio_init(struct bio *bio, struct bio_vec *table, unsigned short max_vecs) { - bio->bi_next = NULL; - bio->bi_bdev = NULL; - bio->bi_opf = 0; - bio->bi_flags = 0; - bio->bi_ioprio = 0; - bio->bi_write_hint = 0; - bio->bi_status = 0; - bio->bi_iter.bi_sector = 0; - bio->bi_iter.bi_size = 0; - bio->bi_iter.bi_idx = 0; - bio->bi_iter.bi_bvec_done = 0; - bio->bi_end_io = NULL; - bio->bi_private = NULL; -#ifdef CONFIG_BLK_CGROUP - bio->bi_blkg = NULL; - bio->bi_issue.value = 0; -#ifdef CONFIG_BLK_CGROUP_IOCOST - bio->bi_iocost_cost = 0; -#endif -#endif -#ifdef CONFIG_BLK_INLINE_ENCRYPTION - bio->bi_crypt_context = NULL; -#endif -#ifdef CONFIG_BLK_DEV_INTEGRITY - bio->bi_integrity = NULL; -#endif - bio->bi_vcnt = 0; - - atomic_set(&bio->__bi_remaining, 1); - atomic_set(&bio->__bi_cnt, 1); - - bio->bi_max_vecs = max_vecs; - bio->bi_io_vec = table; - bio->bi_pool = NULL; + *bio = (struct bio) { + .__bi_remaining = ATOMIC_INIT(1), + .__bi_cnt = ATOMIC_INIT(1), + .bi_max_vecs = max_vecs, + .bi_io_vec = table, + }; } EXPORT_SYMBOL(bio_init);