From patchwork Sun Jul 5 08:01:12 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Leizhen (ThunderTown)" X-Patchwork-Id: 11644185 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 1788F13B4 for ; Sun, 5 Jul 2020 08:01:55 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C646D2075B for ; Sun, 5 Jul 2020 08:01:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C646D2075B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id C66778D000B; Sun, 5 Jul 2020 04:01:53 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id C189C8D0001; Sun, 5 Jul 2020 04:01:53 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B2E158D000B; Sun, 5 Jul 2020 04:01:53 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0166.hostedemail.com [216.40.44.166]) by kanga.kvack.org (Postfix) with ESMTP id 996E88D0001 for ; Sun, 5 Jul 2020 04:01:53 -0400 (EDT) Received: from smtpin09.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 09810180AD807 for ; Sun, 5 Jul 2020 08:01:53 +0000 (UTC) X-FDA: 77003278506.09.name54_0b07ed226ea1 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin09.hostedemail.com (Postfix) with ESMTP id 69018180AD806 for ; Sun, 5 Jul 2020 08:01:52 +0000 (UTC) X-Spam-Summary: 1,0,0,,d41d8cd98f00b204,thunder.leizhen@huawei.com,,RULES_HIT:30012:30051:30054:30056:30070:30090,0,RBL:45.249.212.35:@huawei.com:.lbl8.mailshell.net-64.95.201.95 62.18.2.100;04y8oye4g69d6ofoy1zo5hu9kso8ooccgc34465ae8obdx8ria7qirg1wm4txuc.kc6kgdqd6bt86h183he8keptw5itzs4uho9kahykw6jjmjerwjo4kmx5qogzis7.e-lbl8.mailshell.net-223.238.255.100,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fp,MSBL:0,DNSBL:neutral,Custom_rules:0:0:0,LFtime:23,LUA_SUMMARY:none X-HE-Tag: name54_0b07ed226ea1 X-Filterd-Recvd-Size: 2952 Received: from huawei.com (szxga07-in.huawei.com [45.249.212.35]) by imf38.hostedemail.com (Postfix) with ESMTP for ; Sun, 5 Jul 2020 08:01:48 +0000 (UTC) Received: from DGGEMS402-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 8258FC793171E05A2FD4; Sun, 5 Jul 2020 16:01:42 +0800 (CST) Received: from DESKTOP-C3MD9UG.china.huawei.com (10.174.177.253) by DGGEMS402-HUB.china.huawei.com (10.3.19.202) with Microsoft SMTP Server id 14.3.487.0; Sun, 5 Jul 2020 16:01:31 +0800 From: Zhen Lei To: Andrew Morton , linux-mm , linux-kernel CC: Zhen Lei Subject: [PATCH 1/1] mm/mmap: optimize a branch judgment in ksys_mmap_pgoff() Date: Sun, 5 Jul 2020 16:01:12 +0800 Message-ID: <20200705080112.1405-1-thunder.leizhen@huawei.com> X-Mailer: git-send-email 2.26.0.windows.1 MIME-Version: 1.0 X-Originating-IP: [10.174.177.253] X-CFilter-Loop: Reflected X-Rspamd-Queue-Id: 69018180AD806 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Look at the pseudo code below. It's very clear that, the judgement "!is_file_hugepages(file)" at 3) is duplicated to the one at 1), we can use "else if" to avoid it. And the assignment "retval = -EINVAL" at 2) is only needed by the branch 3), because "retval" will be overwritten at 4). No functional change, but it can reduce the code size. Maybe more clearer? Before: text data bss dec hex filename 28733 1590 1 30324 7674 mm/mmap.o After: text data bss dec hex filename 28701 1590 1 30292 7654 mm/mmap.o ====pseudo code====: if (!(flags & MAP_ANONYMOUS)) { ... 1) if (is_file_hugepages(file)) len = ALIGN(len, huge_page_size(hstate_file(file))); 2) retval = -EINVAL; 3) if (unlikely(flags & MAP_HUGETLB && !is_file_hugepages(file))) goto out_fput; } else if (flags & MAP_HUGETLB) { ... } ... 4) retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff); out_fput: ... return retval; Signed-off-by: Zhen Lei --- mm/mmap.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index 59a4682ebf3faed..a7bb2039738528f 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1562,11 +1562,12 @@ unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len, file = fget(fd); if (!file) return -EBADF; - if (is_file_hugepages(file)) + if (is_file_hugepages(file)) { len = ALIGN(len, huge_page_size(hstate_file(file))); - retval = -EINVAL; - if (unlikely(flags & MAP_HUGETLB && !is_file_hugepages(file))) + } else if (unlikely(flags & MAP_HUGETLB)) { + retval = -EINVAL; goto out_fput; + } } else if (flags & MAP_HUGETLB) { struct user_struct *user = NULL; struct hstate *hs;