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=-15.9 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1,USER_IN_DEF_DKIM_WL autolearn=ham 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 7A858C4CECE for ; Wed, 11 Mar 2020 19:25:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 69EF920578 for ; Wed, 11 Mar 2020 19:25:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="tJy9S47X" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731082AbgCKTZZ (ORCPT ); Wed, 11 Mar 2020 15:25:25 -0400 Received: from mail-pl1-f196.google.com ([209.85.214.196]:37527 "EHLO mail-pl1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730705AbgCKTZY (ORCPT ); Wed, 11 Mar 2020 15:25:24 -0400 Received: by mail-pl1-f196.google.com with SMTP id f16so1550102plj.4 for ; Wed, 11 Mar 2020 12:25:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:in-reply-to:message-id:references :user-agent:mime-version; bh=59QKAlzCo20PiQ6XPvSINe/khVSjSi/vS+Up1F5ddTg=; b=tJy9S47XsErD9oAp5TQAHmEdVwCNzJg333+Gy7Dlv21uAd8nU1x7ZpuifPgBjoculb sGalFcr7RFjYphFG2DvQBkeG0w5ni2bDBdZ4cs9ft/rgRgtTjf+kMvomd7yGOmTvQHJa CqpH98qYxbnJ8HHaDo9NulzM+xrnpbYirmo2sZ/NUWSX7QzV2Rz/b/eAU5ObibbUxGsS AcxDHhlRrSCq2lLPMx1G5wPuV0G5hWDSdp0bQt+M3DBDsiHlTa7/yIOmJtzQR/b3584i kI61/xtVUcu7Cdm1DtV9kdW5t8xUKC3zz0apPNgkltrgo5dC/oECbZ8jj3Jk/+tUQ+qG C/ag== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:in-reply-to:message-id :references:user-agent:mime-version; bh=59QKAlzCo20PiQ6XPvSINe/khVSjSi/vS+Up1F5ddTg=; b=EOquGaStyB29wUJ3B+rMOsmppayN/wXHyiHajTewKodMPDydjf/tTRHrgs5Jyd3FJH S3/hMef1Yz7/EBhlFuecSsrPMOJK3JGGLrkqwo6nhpCl/7Y1SRYeQPkM+MspjCYUx5OD 3x0LPiCrort7JF+Lwc99304aVuaVNCu1Utw69Lqi5LUpcY2tDorNqIkKP8PZOZOw4TYZ dULifwCjsqQkAz//SyY96F14TvJKunLUCDnbWjlfhFsiWgxkVAGoqVTZLP7j9g1TtANB GKKkN2/N0vjx07IQy/Shj3rf6H4i6aV+9B98nxTTzuaAKVHc89ghXDNSu3DyY8OKW92L Uokg== X-Gm-Message-State: ANhLgQ0ZqhT6KB82eR+gIdORhPQz+gD5her9EpkqXqsYk7WBjT4WSRMH bTgVoVP6CHW/FY0jH9XjDEro2Q== X-Google-Smtp-Source: ADFU+vvGy/3Y8m+ciEShHUjkL41A4fyea2QqLF/s4Hpnsgky8XaD+bP70av2ha97jBPDDKorvNbFsA== X-Received: by 2002:a17:902:8f8e:: with SMTP id z14mr4487286plo.195.1583954722155; Wed, 11 Mar 2020 12:25:22 -0700 (PDT) Received: from [2620:15c:17:3:3a5:23a7:5e32:4598] ([2620:15c:17:3:3a5:23a7:5e32:4598]) by smtp.gmail.com with ESMTPSA id s126sm29094656pfb.143.2020.03.11.12.25.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Mar 2020 12:25:21 -0700 (PDT) Date: Wed, 11 Mar 2020 12:25:20 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Vlastimil Babka , Neha Agarwal cc: Mike Kravetz , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A . Shutemov" Subject: Re: [PATCH] mm/hugetlb: remove unnecessary memory fetch in PageHeadHuge() In-Reply-To: <20200311172440.6988-1-vbabka@suse.cz> Message-ID: References: <20200311172440.6988-1-vbabka@suse.cz> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 11 Mar 2020, Vlastimil Babka wrote: > Commit f1e61557f023 ("mm: pack compound_dtor and compound_order into one word > in struct page") changed compound_dtor from a pointer to an array index in > order to pack it. To check if page has the hugeltbfs compound_dtor, we can > just compare the index directly without fetching the function pointer. > Said commit did that with PageHuge() and we can do the same with PageHeadHuge() > to make the code a bit smaller and faster. > > Signed-off-by: Vlastimil Babka > Cc: Mike Kravetz > Cc: Kirill A. Shutemov Fixes: f1e61557f023 ("mm: pack compound_dtor and compound_order into one word in struct page") Acked-by: David Rientjes [+nehaagarwal] We've been running with this patch for a few years and it works as intended. > --- > mm/hugetlb.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index dd8737a94bec..ba1ca452aa7f 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -1313,7 +1313,7 @@ int PageHeadHuge(struct page *page_head) > if (!PageHead(page_head)) > return 0; > > - return get_compound_page_dtor(page_head) == free_huge_page; > + return page_head[1].compound_dtor == HUGETLB_PAGE_DTOR; > } > > pgoff_t __basepage_index(struct page *page) 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=-15.9 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1,USER_IN_DEF_DKIM_WL autolearn=ham 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 499A8C0044D for ; 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Wed, 11 Mar 2020 12:25:21 -0700 (PDT) Date: Wed, 11 Mar 2020 12:25:20 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Vlastimil Babka , Neha Agarwal cc: Mike Kravetz , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A . Shutemov" Subject: Re: [PATCH] mm/hugetlb: remove unnecessary memory fetch in PageHeadHuge() In-Reply-To: <20200311172440.6988-1-vbabka@suse.cz> Message-ID: References: <20200311172440.6988-1-vbabka@suse.cz> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII 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: On Wed, 11 Mar 2020, Vlastimil Babka wrote: > Commit f1e61557f023 ("mm: pack compound_dtor and compound_order into one word > in struct page") changed compound_dtor from a pointer to an array index in > order to pack it. To check if page has the hugeltbfs compound_dtor, we can > just compare the index directly without fetching the function pointer. > Said commit did that with PageHuge() and we can do the same with PageHeadHuge() > to make the code a bit smaller and faster. > > Signed-off-by: Vlastimil Babka > Cc: Mike Kravetz > Cc: Kirill A. Shutemov Fixes: f1e61557f023 ("mm: pack compound_dtor and compound_order into one word in struct page") Acked-by: David Rientjes [+nehaagarwal] We've been running with this patch for a few years and it works as intended. > --- > mm/hugetlb.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index dd8737a94bec..ba1ca452aa7f 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -1313,7 +1313,7 @@ int PageHeadHuge(struct page *page_head) > if (!PageHead(page_head)) > return 0; > > - return get_compound_page_dtor(page_head) == free_huge_page; > + return page_head[1].compound_dtor == HUGETLB_PAGE_DTOR; > } > > pgoff_t __basepage_index(struct page *page)