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=-7.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 08C56C433E3 for ; Fri, 7 Aug 2020 06:23:03 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A6B432177B for ; Fri, 7 Aug 2020 06:23:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="Cj30MXfi" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A6B432177B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 41E3B8D0071; Fri, 7 Aug 2020 02:23:02 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3CF4F8D0026; Fri, 7 Aug 2020 02:23:02 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2E8778D0071; Fri, 7 Aug 2020 02:23:02 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0082.hostedemail.com [216.40.44.82]) by kanga.kvack.org (Postfix) with ESMTP id 188758D0026 for ; Fri, 7 Aug 2020 02:23:02 -0400 (EDT) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id D69A7180AD801 for ; Fri, 7 Aug 2020 06:23:01 +0000 (UTC) X-FDA: 77122779762.25.sign44_2017cd226fbe Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin25.hostedemail.com (Postfix) with ESMTP id A69C61804E3A0 for ; Fri, 7 Aug 2020 06:23:01 +0000 (UTC) X-HE-Tag: sign44_2017cd226fbe X-Filterd-Recvd-Size: 3419 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf11.hostedemail.com (Postfix) with ESMTP for ; Fri, 7 Aug 2020 06:23:01 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 585CB22C9F; Fri, 7 Aug 2020 06:23:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1596781380; bh=AAmWkQvvZBKmqp4aVbr8oXCk1LrZkBLh/2YaYAxgK/U=; h=Date:From:To:Subject:In-Reply-To:From; b=Cj30MXfiy9vJN/28rFSojY1S7+uKUeVky0Nee9JE3nGxA+jXmfIWGvsJRxTDZPyXI wUsiVETGTDVNMS9QQqwrH04DudmDsq0X2hovoxkyHsOFGgfcbFRhY9wkkQtSk5Km1P 6wSoPu2LEm3aYm8+mvPaDH+83jgJASTNaChtHx7s= Date: Thu, 06 Aug 2020 23:22:59 -0700 From: Andrew Morton To: akpm@linux-foundation.org, linux-mm@kvack.org, mm-commits@vger.kernel.org, thunder.leizhen@huawei.com, torvalds@linux-foundation.org Subject: [patch 104/163] mm/mmap: optimize a branch judgment in ksys_mmap_pgoff() Message-ID: <20200807062259.JNE-ENp6G%akpm@linux-foundation.org> In-Reply-To: <20200806231643.a2711a608dd0f18bff2caf2b@linux-foundation.org> User-Agent: s-nail v14.8.16 X-Rspamd-Queue-Id: A69C61804E3A0 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 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: From: Zhen Lei Subject: mm/mmap: optimize a branch judgment in ksys_mmap_pgoff() 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; Link: http://lkml.kernel.org/r/20200705080112.1405-1-thunder.leizhen@huawei.com Signed-off-by: Zhen Lei Reviewed-by: Andrew Morton Signed-off-by: Andrew Morton --- mm/mmap.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- a/mm/mmap.c~mm-mmap-optimize-a-branch-judgment-in-ksys_mmap_pgoff +++ a/mm/mmap.c @@ -1562,11 +1562,12 @@ unsigned long ksys_mmap_pgoff(unsigned l 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; _