Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933253AbcCNBHU (ORCPT ); Sun, 13 Mar 2016 21:07:20 -0400 Received: from mail-yw0-f180.google.com ([209.85.161.180]:32936 "EHLO mail-yw0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932513AbcCNBHO (ORCPT ); Sun, 13 Mar 2016 21:07:14 -0400 MIME-Version: 1.0 In-Reply-To: References: Date: Mon, 14 Mar 2016 09:07:12 +0800 Message-ID: Subject: Re: [PATCH] direct-io: Deinline dio_zero_block, save 2684 bytes From: Ming Lei To: Denys Vlasenko Cc: Denys Vlasenko , Al Viro , Jens Axboe , Christoph Hellwig , Linux Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1294 Lines: 35 On Mon, Mar 14, 2016 at 5:36 AM, Denys Vlasenko wrote: > On Sun, Mar 13, 2016 at 10:00 PM, Denys Vlasenko wrote: >> This function compiles to 2684 bytes, 2 callsites >> >> text data bss dec hex filename >> 9655 16 0 9671 25c7 direct-io.o.before2 >> 9559 16 0 9575 2567 direct-io.o > > Al, you undoubtedly noticed the discrepancy between > "save 2684 bytes" claim in the commit description > and the above data, which shows no such thing. > > Sorry, I was too quick to send the mail to notice it :( > > Further investigation had shown that it's my particular version of gcc > deciding to deinline the function even before the patch. > Other version of gcc, on a different machine was running > large inlining search script, did not do that, and saw the 2684 bytes > of savings. > > tl;dr: the patch is correct, my "size" printout wasn't. Not sure the patch is correct, please see the commit for do_blockdev_direct_IO(): * NOTE: if you pass "sdio" to anything by pointer make sure that function * is always inlined. Otherwise gcc is unable to split the structure into * individual fields and will generate much worse code. This is important * for the whole file. thanks, Ming Lei