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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3405DC25B06 for ; Thu, 11 Aug 2022 23:08:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236614AbiHKXIC (ORCPT ); Thu, 11 Aug 2022 19:08:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41088 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236178AbiHKXIB (ORCPT ); Thu, 11 Aug 2022 19:08:01 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9644EA061B for ; Thu, 11 Aug 2022 16:08:00 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 4D85AB822F6 for ; Thu, 11 Aug 2022 23:07:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E043CC433D6; Thu, 11 Aug 2022 23:07:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1660259278; bh=1nLoFT0eORXl/o0D0yJYIfqLDhaDkMyUopMt+ERrnCg=; h=Date:To:From:Subject:From; b=DXewEi42g0UcfvfE/Q1rVGF8xOWCPafTMuuncqEJxB2C5HFpg+IUbfoGpFo1y+oSX p6/qo+0iN9J1FZDP1Jk87oVefIW6E4iqwyHPxneLNyGwH5jYy41vJw2Egz1Sv+eRdd /jI49nvlz/0Of0+AW1AY7YlLuRL/i07Oum9da3eY= Date: Thu, 11 Aug 2022 16:07:57 -0700 To: mm-commits@vger.kernel.org, willy@infradead.org, kasong@tencent.com, akpm@linux-foundation.org From: Andrew Morton Subject: + mm-util-reduce-stack-usage-of-folio_mapcount.patch added to mm-unstable branch Message-Id: <20220811230757.E043CC433D6@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: mm/util: reduce stack usage of folio_mapcount has been added to the -mm mm-unstable branch. Its filename is mm-util-reduce-stack-usage-of-folio_mapcount.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-util-reduce-stack-usage-of-folio_mapcount.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Kairui Song Subject: mm/util: reduce stack usage of folio_mapcount Date: Tue, 2 Aug 2022 01:31:55 +0800 folio_entire_mapcount() will call PageHeadHuge which is a function call, and blocks the compiler from recognizing this redundant load. After rearranging the code, stack usage is dropped from 32 to 24, and the function size is smaller (tested on GCC 12): Before: Stack usage: mm/util.c:845:5:folio_mapcount 32 static Size: 0000000000000ea0 00000000000000c7 T folio_mapcount After: Stack usage: mm/util.c:845:5:folio_mapcount 24 static Size: 0000000000000ea0 00000000000000b0 T folio_mapcount Link: https://lkml.kernel.org/r/20220801173155.92008-1-ryncsn@gmail.com Signed-off-by: Kairui Song Cc: Matthew Wilcox Signed-off-by: Andrew Morton --- mm/util.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/util.c~mm-util-reduce-stack-usage-of-folio_mapcount +++ a/mm/util.c @@ -850,10 +850,10 @@ int folio_mapcount(struct folio *folio) return atomic_read(&folio->_mapcount) + 1; compound = folio_entire_mapcount(folio); - nr = folio_nr_pages(folio); if (folio_test_hugetlb(folio)) return compound; ret = compound; + nr = folio_nr_pages(folio); for (i = 0; i < nr; i++) ret += atomic_read(&folio_page(folio, i)->_mapcount) + 1; /* File pages has compound_mapcount included in _mapcount */ _ Patches currently in -mm which might be from kasong@tencent.com are mm-util-reduce-stack-usage-of-folio_mapcount.patch