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=-3.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 02AC0C4361B for ; Thu, 10 Dec 2020 13:31:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AE0F423DE8 for ; Thu, 10 Dec 2020 13:31:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389263AbgLJNbY (ORCPT ); Thu, 10 Dec 2020 08:31:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51584 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389209AbgLJNbJ (ORCPT ); Thu, 10 Dec 2020 08:31:09 -0500 Received: from mail-pl1-x642.google.com (mail-pl1-x642.google.com [IPv6:2607:f8b0:4864:20::642]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 07759C061794 for ; Thu, 10 Dec 2020 05:30:29 -0800 (PST) Received: by mail-pl1-x642.google.com with SMTP id x12so2298239plr.10 for ; Thu, 10 Dec 2020 05:30:29 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=tlXbD+UEW4Nv5CZk4BO09R9ymA6io2nhExNKSLuSREQ=; b=XEetfo9+rdFZ5g2HSecX62Vb83yVOQ4YXuxvIr2WX+3p4DuQGaZU6eU8CUT1vg6+Mb m8jJJFkKTc7U0a/C0aZOxg5CoEh0eW3IEEMZyEdgKcdjNbMiWqS9tUO75mojAmglH13G xs6aqo8pMw6GyO36bz7qI1tSyUk6f49dHEVlQqqgZqxUPHX9MUWx+16CR8r36dhWyKvS IuPCk7YP6uXuQf6dWn59o73V2Sn7TMRIE6Vzd5YLhVTUknu6cvsJWwTU1l8JEOfybJqs JNdvkSIfHvqtGEHpXNKiwgSHVJdxvRk7Uoz7m04WOmHXVpcm5mwqAOX6J5BTRjpP6wvE A3vA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=tlXbD+UEW4Nv5CZk4BO09R9ymA6io2nhExNKSLuSREQ=; b=axPnDkatbRxBqlHLYxJVAXPATijyAs5nQbvi4A0cNuB6+xnKDRvPiyg/WLDBxSsApp 667hVgWRjoaeLKZlFtoMRojbO9mIg13ysIDrdaRG/IsYjN+hLq/zQdSsIMwr1XfXcO5W eLE2dAWLoFSaXaXY/z0IykD1d7F5zR3JgNXSQSjaRohnQFyc/EhNT6d1uhO7yIVedCFo daWsB1bCpSWuc/HsvLmYLv73U2mTFU5FS/PII23mY8QJyva2bV+kZHyyq4HGqnZ2egsB c/oyUfxfNvtnZphRRxca0d4sSatdfTBHMwvTU3+dzP9loOCVyXXrpui09tuzIaYyk5nT wFKQ== X-Gm-Message-State: AOAM531viPovR6f8ah+Nl9h2ipSMmezmztGtYnvlFPm0Nk7IQeeqtesP noMl+onVeOrbWBNG3szkVUtw7TQ07pWvIAm3GaTCBw== X-Google-Smtp-Source: ABdhPJyIxJlJPOzma7jwGPoMV3ur6Fu8hZQ/SgquqvsnBCzV9+EcBlQ5INuf2+vkcKklIzEA1H5DJlf1FTH47OaC8BE= X-Received: by 2002:a17:902:ed0d:b029:da:c83b:5f40 with SMTP id b13-20020a170902ed0db02900dac83b5f40mr6598545pld.20.1607607028567; Thu, 10 Dec 2020 05:30:28 -0800 (PST) MIME-Version: 1.0 References: <20201210035526.38938-1-songmuchun@bytedance.com> <20201210035526.38938-13-songmuchun@bytedance.com> <375d6bad6bb37e3626f71bfabc20b384@suse.de> <20201210131608.GA7811@localhost.localdomain> In-Reply-To: <20201210131608.GA7811@localhost.localdomain> From: Muchun Song Date: Thu, 10 Dec 2020 21:29:51 +0800 Message-ID: Subject: Re: [External] Re: [PATCH v8 12/12] mm/hugetlb: Optimize the code with the help of the compiler To: Oscar Salvador Cc: Jonathan Corbet , Mike Kravetz , Thomas Gleixner , mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, Peter Zijlstra , viro@zeniv.linux.org.uk, Andrew Morton , paulmck@kernel.org, mchehab+huawei@kernel.org, pawan.kumar.gupta@linux.intel.com, Randy Dunlap , oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de, Mina Almasry , David Rientjes , Matthew Wilcox , Michal Hocko , "Song Bao Hua (Barry Song)" , David Hildenbrand , Xiongchun duan , linux-doc@vger.kernel.org, LKML , Linux Memory Management List , linux-fsdevel Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 10, 2020 at 9:16 PM Oscar Salvador wrote: > > On Thu, Dec 10, 2020 at 08:14:18PM +0800, Muchun Song wrote: > > Yeah, you are right. But if we do this check can make the code simple. > > > > For example, here is a code snippet. > > > > void func(void) > > { > > if (free_vmemmap_pages_per_hpage()) > > return; > > /* Do something */ > > } > > > > With this patch, the func will be optimized to null when is_power_of_2 > > returns false. > > > > void func(void) > > { > > } > > > > Without this patch, the compiler cannot do this optimization. > > Ok, I misread the changelog. > > So, then is_hugetlb_free_vmemmap_enabled, free_huge_page_vmemmap, > free_vmemmap_pages_per_hpage and hugetlb_vmemmap_init are optimized > out, right? Yes, that's right. I have disassembled to make sure of this. Thanks. > > -- > Oscar Salvador > SUSE L3 -- Yours, Muchun