From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [PATCH v3] mm: Avoid unnecessary page fault retires on shared memory types Date: Fri, 27 May 2022 12:46:31 +0200 Message-ID: References: <20220524234531.1949-1-peterx@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=47i+0uT2HqlxUZF0qinCS+6HQPb+VCxF4jmzUSqdgJM=; b=HmBEiYbuNlU/U1 fso0v5kOz6Y7beIbTteqqLUEu02mTIIuGuY34eEaSCz5dHAl8PDMf/TbNJmZ5A31ZkQeDwNEIIsKT Z/SGTYXgvj2QCuNdBPsmii9qlkLKycgN48u0gOlQrqMHjW3O5w8mblHIERsLadJfzssKUrrFcCWuo Wg6pTvnadd6/7bTsYt6BI1Uer+4FfnvzrenyHDX+FotZzi+P7+5OuzAj2UMVsVKfhMAVYtSLTxAW6 wTxJXresqHxr9lwIlTvFmtYzIho//ggBEz+wuXKDEk2alZy8buF5IKS3N8kue0FG/BK9P+ZnAm3I1 8dEcRsqLFD7OqyY3VOpA==; DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=VEAekRrz/FSY4pk4QnV3m6H5QVjhz8BFDYr0EcpVw1E=; b=nXTl96gpCDbYy3bbmZHUFxanwBKanpTD5T3ye91nNt0S5DzRS50X+C3V5calou/Tbd W3tp+Pa5ui5nyk/J9IilzxqUhKzX+QyGcukjZk0ELfa/RtKrZMaq9i+yE1j0RcYeHGEH V+4RtLXDWPxnAymJMfcVpu0JZEZoxenwNXkmgyYKMQXGnN1Ls7NkOSx9TgW4IEazH0HS TOy4lNsQjFRd71dz5D/Ux8BGGU+UgNurAc7P2zcBMC8bJFwbS5pJWekOq461oc+DsRDd eh87WbfBiCTIu2NxwA+S3LoC7J0WxrnESI1Jt77XHjKjToAke3bka2tT28oXpFfiDYxk GFbg== Content-Disposition: inline In-Reply-To: <20220524234531.1949-1-peterx@redhat.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-riscv" Errors-To: linux-riscv-bounces+glpr-linux-riscv=m.gmane-mx.org@lists.infradead.org To: Peter Xu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Richard Henderson , David Hildenbrand , Matt Turner , Albert Ou , Michal Simek , Russell King , Ivan Kokshaysky , linux-riscv@lists.infradead.org, Alexander Gordeev , Dave Hansen , Jonas Bonn , Will Deacon , "James E . J . Bottomley" , "H . Peter Anvin" , Andrea Arcangeli , openrisc@lists.librecores.org, linux-s390@vger.kernel.org, Ingo Molnar , linux-m68k@lists.linux-m68k.org, Palmer Dabbelt , Heiko Carstens , Chris Zankel , Peter * Peter Xu wrote: > This patch provides a ~12% perf boost on my aarch64 test VM with a simple > program sequentially dirtying 400MB shmem file being mmap()ed and these are > the time it needs: > > Before: 650.980 ms (+-1.94%) > After: 569.396 ms (+-1.38%) Nice! > arch/x86/mm/fault.c | 4 ++++ Reviewed-by: Ingo Molnar Minor comment typo: > + /* > + * We should do the same as VM_FAULT_RETRY, but let's not > + * return -EBUSY since that's not reflecting the reality on > + * what has happened - we've just fully completed a page > + * fault, with the mmap lock released. Use -EAGAIN to show > + * that we want to take the mmap lock _again_. > + */ s/reflecting the reality on what has happened /reflecting the reality of what has happened > ret = handle_mm_fault(vma, address, fault_flags, NULL); > + > + if (ret & VM_FAULT_COMPLETED) { > + /* > + * NOTE: it's a pity that we need to retake the lock here > + * to pair with the unlock() in the callers. Ideally we > + * could tell the callers so they do not need to unlock. > + */ > + mmap_read_lock(mm); > + *unlocked = true; > + return 0; Indeed that's a pity - I guess more performance could be gained here, especially in highly parallel threaded workloads? Thanks, Ingo 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 EA9E8C433F5 for ; Fri, 27 May 2022 10:46:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234373AbiE0Kqs (ORCPT ); Fri, 27 May 2022 06:46:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51052 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344688AbiE0Kqi (ORCPT ); Fri, 27 May 2022 06:46:38 -0400 Received: from mail-ej1-x62f.google.com (mail-ej1-x62f.google.com [IPv6:2a00:1450:4864:20::62f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 248E4140E2; Fri, 27 May 2022 03:46:37 -0700 (PDT) Received: by mail-ej1-x62f.google.com with SMTP id m20so7894959ejj.10; Fri, 27 May 2022 03:46:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=VEAekRrz/FSY4pk4QnV3m6H5QVjhz8BFDYr0EcpVw1E=; b=nXTl96gpCDbYy3bbmZHUFxanwBKanpTD5T3ye91nNt0S5DzRS50X+C3V5calou/Tbd W3tp+Pa5ui5nyk/J9IilzxqUhKzX+QyGcukjZk0ELfa/RtKrZMaq9i+yE1j0RcYeHGEH V+4RtLXDWPxnAymJMfcVpu0JZEZoxenwNXkmgyYKMQXGnN1Ls7NkOSx9TgW4IEazH0HS TOy4lNsQjFRd71dz5D/Ux8BGGU+UgNurAc7P2zcBMC8bJFwbS5pJWekOq461oc+DsRDd eh87WbfBiCTIu2NxwA+S3LoC7J0WxrnESI1Jt77XHjKjToAke3bka2tT28oXpFfiDYxk GFbg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=VEAekRrz/FSY4pk4QnV3m6H5QVjhz8BFDYr0EcpVw1E=; b=LO/1f7GqF0w+xraxHPRErJiYfcdeZvbNzV9YGGojCAY5Bupb1bp0W3LZctCENfsFtR /WAKDzDKat2OkwGPW6D9fTl8fLj4Etmld6CZcJPticTjrF4H+haFomQ5h2e2HbYEdbs9 rJXKpbLU4YBYdRz+DOOZSbUePDCap7/oqhjphJIaE5H/vNGTmKGyWs34XdICGbJfAF2E FnHaX6s/oiFnVrTvwhnGudEJM0wErbTqenz+2gjOQJe2b/lD6oLvnqlQCGKjtFr1Yece d/2nPYfV3C7ZHShCeCpBEDW/M2LNQKNi0ij4kNVyvIb3aU7A7WLEEfAmvHnsZOmvVZPm eUGQ== X-Gm-Message-State: AOAM530kWFv/pmgO/9MV407r0PZ0iD3pk3N1Wphwja2DI6Sdq8+O0cTf 4C7lKcUVxCvRV2qALA5lixmZBgoYiWo= X-Google-Smtp-Source: ABdhPJyWn7wVchQLELsEVq6TA/gUzEaBn19VUAXtFTYBInhQr0sSQqMx29HcpQwhBHqmmOM8Z+iT0g== X-Received: by 2002:a17:907:7baa:b0:6fe:b3dc:2378 with SMTP id ne42-20020a1709077baa00b006feb3dc2378mr30766036ejc.266.1653648395645; Fri, 27 May 2022 03:46:35 -0700 (PDT) Received: from gmail.com (563BA16F.dsl.pool.telekom.hu. [86.59.161.111]) by smtp.gmail.com with ESMTPSA id i20-20020a17090639d400b006fec1a73e48sm1320742eje.64.2022.05.27.03.46.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 May 2022 03:46:34 -0700 (PDT) Sender: Ingo Molnar Date: Fri, 27 May 2022 12:46:31 +0200 From: Ingo Molnar To: Peter Xu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Richard Henderson , David Hildenbrand , Matt Turner , Albert Ou , Michal Simek , Russell King , Ivan Kokshaysky , linux-riscv@lists.infradead.org, Alexander Gordeev , Dave Hansen , Jonas Bonn , Will Deacon , "James E . J . Bottomley" , "H . Peter Anvin" , Andrea Arcangeli , openrisc@lists.librecores.org, linux-s390@vger.kernel.org, Ingo Molnar , linux-m68k@lists.linux-m68k.org, Palmer Dabbelt , Heiko Carstens , Chris Zankel , Peter Zijlstra , Alistair Popple , linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, Vlastimil Babka , Thomas Gleixner , sparclinux@vger.kernel.org, Christian Borntraeger , Stafford Horne , Michael Ellerman , x86@kernel.org, Thomas Bogendoerfer , Paul Mackerras , linux-arm-kernel@lists.infradead.org, Sven Schnelle , Benjamin Herrenschmidt , linux-xtensa@linux-xtensa.org, Nicholas Piggin , linux-sh@vger.kernel.org, Vasily Gorbik , Borislav Petkov , linux-mips@vger.kernel.org, Max Filippov , Helge Deller , Vineet Gupta , Al Viro , Paul Walmsley , Johannes Weiner , Anton Ivanov , Catalin Marinas , linux-um@lists.infradead.org, linux-alpha@vger.kernel.org, Johannes Berg , linux-ia64@vger.kernel.org, Geert Uytterhoeven , Dinh Nguyen , Guo Ren , linux-snps-arc@lists.infradead.org, Hugh Dickins , Rich Felker , Andy Lutomirski , Richard Weinberger , linuxppc-dev@lists.ozlabs.org, Brian Cain , Yoshinori Sato , Andrew Morton , Stefan Kristiansson , linux-parisc@vger.kernel.org, "David S . Miller" Subject: Re: [PATCH v3] mm: Avoid unnecessary page fault retires on shared memory types Message-ID: References: <20220524234531.1949-1-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220524234531.1949-1-peterx@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-csky@vger.kernel.org * Peter Xu wrote: > This patch provides a ~12% perf boost on my aarch64 test VM with a simple > program sequentially dirtying 400MB shmem file being mmap()ed and these are > the time it needs: > > Before: 650.980 ms (+-1.94%) > After: 569.396 ms (+-1.38%) Nice! > arch/x86/mm/fault.c | 4 ++++ Reviewed-by: Ingo Molnar Minor comment typo: > + /* > + * We should do the same as VM_FAULT_RETRY, but let's not > + * return -EBUSY since that's not reflecting the reality on > + * what has happened - we've just fully completed a page > + * fault, with the mmap lock released. Use -EAGAIN to show > + * that we want to take the mmap lock _again_. > + */ s/reflecting the reality on what has happened /reflecting the reality of what has happened > ret = handle_mm_fault(vma, address, fault_flags, NULL); > + > + if (ret & VM_FAULT_COMPLETED) { > + /* > + * NOTE: it's a pity that we need to retake the lock here > + * to pair with the unlock() in the callers. Ideally we > + * could tell the callers so they do not need to unlock. > + */ > + mmap_read_lock(mm); > + *unlocked = true; > + return 0; Indeed that's a pity - I guess more performance could be gained here, especially in highly parallel threaded workloads? Thanks, Ingo From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Date: Fri, 27 May 2022 10:46:31 +0000 Subject: Re: [PATCH v3] mm: Avoid unnecessary page fault retires on shared memory types Message-Id: List-Id: References: <20220524234531.1949-1-peterx@redhat.com> In-Reply-To: <20220524234531.1949-1-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Peter Xu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Richard Henderson , David Hildenbrand , Matt Turner , Albert Ou , Michal Simek , Russell King , Ivan Kokshaysky , linux-riscv@lists.infradead.org, Alexander Gordeev , Dave Hansen , Jonas Bonn , Will Deacon , "James E . J . Bottomley" , "H . Peter Anvin" , Andrea Arcangeli , openrisc@lists.librecores.org, linux-s390@vger.kernel.org, Ingo Molnar , linux-m68k@lists.linux-m68k.org, Palmer Dabbelt , Heiko Carstens , Chris Zankel , Peter Zijlstra , Alistair Popple , linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, Vlastimil Babka , Thomas Gleixner , sparclinux@vger.kernel.org, Christian Borntraeger , Stafford Horne , Michael Ellerman , x86@kernel.org, Thomas Bogendoerfer , Paul Mackerras , linux-arm-kernel@lists.infradead.org, Sven Schnelle , Benjamin Herrenschmidt , linux-xtensa@linux-xtensa.org, Nicholas Piggin , linux-sh@vger.kernel.org, Vasily Gorbik , Borislav Petkov , linux-mips@vger.kernel.org, Max Filippov , Helge Deller , Vineet Gupta , Al Viro , Paul Walmsley , Johannes Weiner , Anton Ivanov , Catalin Marinas , linux-um@lists.infradead.org, linux-alpha@vger.kernel.org, Johannes Berg , linux-ia64@vger.kernel.org, Geert Uytterhoeven , Dinh Nguyen , Guo Ren , linux-snps-arc@lists.infradead.org, Hugh Dickins , Rich Felker , Andy Lutomirski , Richard Weinberger , linuxppc-dev@lists.ozlabs.org, Brian Cain , Yoshinori Sato , Andrew Morton , Stefan Kristiansson , linux-parisc@vger.kernel.org, "David S . Miller" * Peter Xu wrote: > This patch provides a ~12% perf boost on my aarch64 test VM with a simple > program sequentially dirtying 400MB shmem file being mmap()ed and these are > the time it needs: > > Before: 650.980 ms (+-1.94%) > After: 569.396 ms (+-1.38%) Nice! > arch/x86/mm/fault.c | 4 ++++ Reviewed-by: Ingo Molnar Minor comment typo: > + /* > + * We should do the same as VM_FAULT_RETRY, but let's not > + * return -EBUSY since that's not reflecting the reality on > + * what has happened - we've just fully completed a page > + * fault, with the mmap lock released. Use -EAGAIN to show > + * that we want to take the mmap lock _again_. > + */ s/reflecting the reality on what has happened /reflecting the reality of what has happened > ret = handle_mm_fault(vma, address, fault_flags, NULL); > + > + if (ret & VM_FAULT_COMPLETED) { > + /* > + * NOTE: it's a pity that we need to retake the lock here > + * to pair with the unlock() in the callers. Ideally we > + * could tell the callers so they do not need to unlock. > + */ > + mmap_read_lock(mm); > + *unlocked = true; > + return 0; Indeed that's a pity - I guess more performance could be gained here, especially in highly parallel threaded workloads? Thanks, Ingo 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5709FC433F5 for ; Fri, 27 May 2022 10:46:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=47i+0uT2HqlxUZF0qinCS+6HQPb+VCxF4jmzUSqdgJM=; b=HmBEiYbuNlU/U1 fso0v5kOz6Y7beIbTteqqLUEu02mTIIuGuY34eEaSCz5dHAl8PDMf/TbNJmZ5A31ZkQeDwNEIIsKT Z/SGTYXgvj2QCuNdBPsmii9qlkLKycgN48u0gOlQrqMHjW3O5w8mblHIERsLadJfzssKUrrFcCWuo Wg6pTvnadd6/7bTsYt6BI1Uer+4FfnvzrenyHDX+FotZzi+P7+5OuzAj2UMVsVKfhMAVYtSLTxAW6 wTxJXresqHxr9lwIlTvFmtYzIho//ggBEz+wuXKDEk2alZy8buF5IKS3N8kue0FG/BK9P+ZnAm3I1 8dEcRsqLFD7OqyY3VOpA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nuXUQ-00HPha-4L; Fri, 27 May 2022 10:46:42 +0000 Received: from mail-ej1-x62f.google.com ([2a00:1450:4864:20::62f]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nuXUN-00HPfp-Gr; Fri, 27 May 2022 10:46:40 +0000 Received: by mail-ej1-x62f.google.com with SMTP id wh22so7995268ejb.7; Fri, 27 May 2022 03:46:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=VEAekRrz/FSY4pk4QnV3m6H5QVjhz8BFDYr0EcpVw1E=; b=nXTl96gpCDbYy3bbmZHUFxanwBKanpTD5T3ye91nNt0S5DzRS50X+C3V5calou/Tbd W3tp+Pa5ui5nyk/J9IilzxqUhKzX+QyGcukjZk0ELfa/RtKrZMaq9i+yE1j0RcYeHGEH V+4RtLXDWPxnAymJMfcVpu0JZEZoxenwNXkmgyYKMQXGnN1Ls7NkOSx9TgW4IEazH0HS TOy4lNsQjFRd71dz5D/Ux8BGGU+UgNurAc7P2zcBMC8bJFwbS5pJWekOq461oc+DsRDd eh87WbfBiCTIu2NxwA+S3LoC7J0WxrnESI1Jt77XHjKjToAke3bka2tT28oXpFfiDYxk GFbg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=VEAekRrz/FSY4pk4QnV3m6H5QVjhz8BFDYr0EcpVw1E=; b=B7yvlizxxGdscbxbCZNgrEwpXJj8CN4ylDF+qduTpURDhsERDkxIByYwyivkB/fzS/ sqs6Cj/+j9EpE6dRWbwtBhPI9Osb/5jyUOfsjNJuFTIhfl7l+hm9Ic+0nyT64nFHwO89 6/1wukOgpoqTBxbzN8RgCoe5aFxmLmpW3XHhUYnYZRmIJ4IZKqSZ3C16gdckIogoV6ML Wve1ucyV6pB7xDwOOoPP9ByrAjWpEoEOn0d6hhZLb2kutwg9Weon6Dj2li8vXmVD6Bfc ZImTcPnUHgOCEnz+Af2ElS6ZOQIf4i/7oRgrPyhojJ9RZyCJyAZCa2SKmhjhdhpf0MRu JRHA== X-Gm-Message-State: AOAM531Ie6o5fSn+bBKRBc8uA9/lkbD7VOsjy7LbZ4PDdQWO7sd0JRxj B8qdASJdZvWcWsUsqgXdLKk= X-Google-Smtp-Source: ABdhPJyWn7wVchQLELsEVq6TA/gUzEaBn19VUAXtFTYBInhQr0sSQqMx29HcpQwhBHqmmOM8Z+iT0g== X-Received: by 2002:a17:907:7baa:b0:6fe:b3dc:2378 with SMTP id ne42-20020a1709077baa00b006feb3dc2378mr30766036ejc.266.1653648395645; Fri, 27 May 2022 03:46:35 -0700 (PDT) Received: from gmail.com (563BA16F.dsl.pool.telekom.hu. [86.59.161.111]) by smtp.gmail.com with ESMTPSA id i20-20020a17090639d400b006fec1a73e48sm1320742eje.64.2022.05.27.03.46.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 May 2022 03:46:34 -0700 (PDT) Date: Fri, 27 May 2022 12:46:31 +0200 From: Ingo Molnar To: Peter Xu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Richard Henderson , David Hildenbrand , Matt Turner , Albert Ou , Michal Simek , Russell King , Ivan Kokshaysky , linux-riscv@lists.infradead.org, Alexander Gordeev , Dave Hansen , Jonas Bonn , Will Deacon , "James E . J . Bottomley" , "H . Peter Anvin" , Andrea Arcangeli , openrisc@lists.librecores.org, linux-s390@vger.kernel.org, Ingo Molnar , linux-m68k@lists.linux-m68k.org, Palmer Dabbelt , Heiko Carstens , Chris Zankel , Peter Zijlstra , Alistair Popple , linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, Vlastimil Babka , Thomas Gleixner , sparclinux@vger.kernel.org, Christian Borntraeger , Stafford Horne , Michael Ellerman , x86@kernel.org, Thomas Bogendoerfer , Paul Mackerras , linux-arm-kernel@lists.infradead.org, Sven Schnelle , Benjamin Herrenschmidt , linux-xtensa@linux-xtensa.org, Nicholas Piggin , linux-sh@vger.kernel.org, Vasily Gorbik , Borislav Petkov , linux-mips@vger.kernel.org, Max Filippov , Helge Deller , Vineet Gupta , Al Viro , Paul Walmsley , Johannes Weiner , Anton Ivanov , Catalin Marinas , linux-um@lists.infradead.org, linux-alpha@vger.kernel.org, Johannes Berg , linux-ia64@vger.kernel.org, Geert Uytterhoeven , Dinh Nguyen , Guo Ren , linux-snps-arc@lists.infradead.org, Hugh Dickins , Rich Felker , Andy Lutomirski , Richard Weinberger , linuxppc-dev@lists.ozlabs.org, Brian Cain , Yoshinori Sato , Andrew Morton , Stefan Kristiansson , linux-parisc@vger.kernel.org, "David S . Miller" Subject: Re: [PATCH v3] mm: Avoid unnecessary page fault retires on shared memory types Message-ID: References: <20220524234531.1949-1-peterx@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220524234531.1949-1-peterx@redhat.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220527_034639_598366_A074BA1C X-CRM114-Status: GOOD ( 18.98 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org * Peter Xu wrote: > This patch provides a ~12% perf boost on my aarch64 test VM with a simple > program sequentially dirtying 400MB shmem file being mmap()ed and these are > the time it needs: > > Before: 650.980 ms (+-1.94%) > After: 569.396 ms (+-1.38%) Nice! > arch/x86/mm/fault.c | 4 ++++ Reviewed-by: Ingo Molnar Minor comment typo: > + /* > + * We should do the same as VM_FAULT_RETRY, but let's not > + * return -EBUSY since that's not reflecting the reality on > + * what has happened - we've just fully completed a page > + * fault, with the mmap lock released. Use -EAGAIN to show > + * that we want to take the mmap lock _again_. > + */ s/reflecting the reality on what has happened /reflecting the reality of what has happened > ret = handle_mm_fault(vma, address, fault_flags, NULL); > + > + if (ret & VM_FAULT_COMPLETED) { > + /* > + * NOTE: it's a pity that we need to retake the lock here > + * to pair with the unlock() in the callers. Ideally we > + * could tell the callers so they do not need to unlock. > + */ > + mmap_read_lock(mm); > + *unlocked = true; > + return 0; Indeed that's a pity - I guess more performance could be gained here, especially in highly parallel threaded workloads? Thanks, Ingo _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 0237DC433EF for ; Fri, 27 May 2022 10:46:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=QqRAtz25g/azeP71VIUqtR3Bkc/T9LZS5NvlSbJXe20=; b=r+riSwQCUzhm6X pX9lLLWcre7Wt18unRg5Mc85VwbZ2yLP7D1GjhzH8x5jhi7LQhqdyYT7HZ3FJEtWsEOZIN87ylA3U zGIsloUH60Q0hW/cKrM/uU6lf2Okcxnw+YJRs1WHzvsMkI3UrLGhBhfi8BcGIebtk2uzSsmJ2rVJq V63dQnG5dETng1ql0Z+KDIGflB3T+pfMtVCHRZmvd1nL1Z+MF5dRVm4/7PxpPz7RtpVb+27PvIpfX zPjUA92nnM8LzDF0dZCGmOpIQ2vxhrieAbkqgu0K44uOr+hARMDmVs0XgPlVqbCHJuIe6YJuT2Tqj Te4JzHKhheTAoqQSsF1g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nuXUR-00HPiC-Uh; Fri, 27 May 2022 10:46:43 +0000 Received: from mail-ej1-x62f.google.com ([2a00:1450:4864:20::62f]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nuXUN-00HPfp-Gr; Fri, 27 May 2022 10:46:40 +0000 Received: by mail-ej1-x62f.google.com with SMTP id wh22so7995268ejb.7; Fri, 27 May 2022 03:46:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=VEAekRrz/FSY4pk4QnV3m6H5QVjhz8BFDYr0EcpVw1E=; b=nXTl96gpCDbYy3bbmZHUFxanwBKanpTD5T3ye91nNt0S5DzRS50X+C3V5calou/Tbd W3tp+Pa5ui5nyk/J9IilzxqUhKzX+QyGcukjZk0ELfa/RtKrZMaq9i+yE1j0RcYeHGEH V+4RtLXDWPxnAymJMfcVpu0JZEZoxenwNXkmgyYKMQXGnN1Ls7NkOSx9TgW4IEazH0HS TOy4lNsQjFRd71dz5D/Ux8BGGU+UgNurAc7P2zcBMC8bJFwbS5pJWekOq461oc+DsRDd eh87WbfBiCTIu2NxwA+S3LoC7J0WxrnESI1Jt77XHjKjToAke3bka2tT28oXpFfiDYxk GFbg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=VEAekRrz/FSY4pk4QnV3m6H5QVjhz8BFDYr0EcpVw1E=; b=B7yvlizxxGdscbxbCZNgrEwpXJj8CN4ylDF+qduTpURDhsERDkxIByYwyivkB/fzS/ sqs6Cj/+j9EpE6dRWbwtBhPI9Osb/5jyUOfsjNJuFTIhfl7l+hm9Ic+0nyT64nFHwO89 6/1wukOgpoqTBxbzN8RgCoe5aFxmLmpW3XHhUYnYZRmIJ4IZKqSZ3C16gdckIogoV6ML Wve1ucyV6pB7xDwOOoPP9ByrAjWpEoEOn0d6hhZLb2kutwg9Weon6Dj2li8vXmVD6Bfc ZImTcPnUHgOCEnz+Af2ElS6ZOQIf4i/7oRgrPyhojJ9RZyCJyAZCa2SKmhjhdhpf0MRu JRHA== X-Gm-Message-State: AOAM531Ie6o5fSn+bBKRBc8uA9/lkbD7VOsjy7LbZ4PDdQWO7sd0JRxj B8qdASJdZvWcWsUsqgXdLKk= X-Google-Smtp-Source: ABdhPJyWn7wVchQLELsEVq6TA/gUzEaBn19VUAXtFTYBInhQr0sSQqMx29HcpQwhBHqmmOM8Z+iT0g== X-Received: by 2002:a17:907:7baa:b0:6fe:b3dc:2378 with SMTP id ne42-20020a1709077baa00b006feb3dc2378mr30766036ejc.266.1653648395645; Fri, 27 May 2022 03:46:35 -0700 (PDT) Received: from gmail.com (563BA16F.dsl.pool.telekom.hu. [86.59.161.111]) by smtp.gmail.com with ESMTPSA id i20-20020a17090639d400b006fec1a73e48sm1320742eje.64.2022.05.27.03.46.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 May 2022 03:46:34 -0700 (PDT) Date: Fri, 27 May 2022 12:46:31 +0200 From: Ingo Molnar To: Peter Xu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Richard Henderson , David Hildenbrand , Matt Turner , Albert Ou , Michal Simek , Russell King , Ivan Kokshaysky , linux-riscv@lists.infradead.org, Alexander Gordeev , Dave Hansen , Jonas Bonn , Will Deacon , "James E . J . Bottomley" , "H . Peter Anvin" , Andrea Arcangeli , openrisc@lists.librecores.org, linux-s390@vger.kernel.org, Ingo Molnar , linux-m68k@lists.linux-m68k.org, Palmer Dabbelt , Heiko Carstens , Chris Zankel , Peter Zijlstra , Alistair Popple , linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, Vlastimil Babka , Thomas Gleixner , sparclinux@vger.kernel.org, Christian Borntraeger , Stafford Horne , Michael Ellerman , x86@kernel.org, Thomas Bogendoerfer , Paul Mackerras , linux-arm-kernel@lists.infradead.org, Sven Schnelle , Benjamin Herrenschmidt , linux-xtensa@linux-xtensa.org, Nicholas Piggin , linux-sh@vger.kernel.org, Vasily Gorbik , Borislav Petkov , linux-mips@vger.kernel.org, Max Filippov , Helge Deller , Vineet Gupta , Al Viro , Paul Walmsley , Johannes Weiner , Anton Ivanov , Catalin Marinas , linux-um@lists.infradead.org, linux-alpha@vger.kernel.org, Johannes Berg , linux-ia64@vger.kernel.org, Geert Uytterhoeven , Dinh Nguyen , Guo Ren , linux-snps-arc@lists.infradead.org, Hugh Dickins , Rich Felker , Andy Lutomirski , Richard Weinberger , linuxppc-dev@lists.ozlabs.org, Brian Cain , Yoshinori Sato , Andrew Morton , Stefan Kristiansson , linux-parisc@vger.kernel.org, "David S . Miller" Subject: Re: [PATCH v3] mm: Avoid unnecessary page fault retires on shared memory types Message-ID: References: <20220524234531.1949-1-peterx@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220524234531.1949-1-peterx@redhat.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220527_034639_598366_A074BA1C X-CRM114-Status: GOOD ( 18.98 ) X-BeenThere: linux-snps-arc@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Linux on Synopsys ARC Processors List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-snps-arc" Errors-To: linux-snps-arc-bounces+linux-snps-arc=archiver.kernel.org@lists.infradead.org * Peter Xu wrote: > This patch provides a ~12% perf boost on my aarch64 test VM with a simple > program sequentially dirtying 400MB shmem file being mmap()ed and these are > the time it needs: > > Before: 650.980 ms (+-1.94%) > After: 569.396 ms (+-1.38%) Nice! > arch/x86/mm/fault.c | 4 ++++ Reviewed-by: Ingo Molnar Minor comment typo: > + /* > + * We should do the same as VM_FAULT_RETRY, but let's not > + * return -EBUSY since that's not reflecting the reality on > + * what has happened - we've just fully completed a page > + * fault, with the mmap lock released. Use -EAGAIN to show > + * that we want to take the mmap lock _again_. > + */ s/reflecting the reality on what has happened /reflecting the reality of what has happened > ret = handle_mm_fault(vma, address, fault_flags, NULL); > + > + if (ret & VM_FAULT_COMPLETED) { > + /* > + * NOTE: it's a pity that we need to retake the lock here > + * to pair with the unlock() in the callers. Ideally we > + * could tell the callers so they do not need to unlock. > + */ > + mmap_read_lock(mm); > + *unlocked = true; > + return 0; Indeed that's a pity - I guess more performance could be gained here, especially in highly parallel threaded workloads? Thanks, Ingo _______________________________________________ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc 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 mail.librecores.org (lists.librecores.org [88.198.125.70]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8FC7CC433EF for ; Fri, 27 May 2022 10:46:38 +0000 (UTC) Received: from [172.31.1.100] (localhost.localdomain [127.0.0.1]) by mail.librecores.org (Postfix) with ESMTP id 2CACC247C4; Fri, 27 May 2022 12:46:37 +0200 (CEST) Received: from mail-ej1-f45.google.com (mail-ej1-f45.google.com [209.85.218.45]) by mail.librecores.org (Postfix) with ESMTPS id 103562431F for ; Fri, 27 May 2022 12:46:36 +0200 (CEST) Received: by mail-ej1-f45.google.com with SMTP id m20so7894961ejj.10 for ; Fri, 27 May 2022 03:46:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=VEAekRrz/FSY4pk4QnV3m6H5QVjhz8BFDYr0EcpVw1E=; b=nXTl96gpCDbYy3bbmZHUFxanwBKanpTD5T3ye91nNt0S5DzRS50X+C3V5calou/Tbd W3tp+Pa5ui5nyk/J9IilzxqUhKzX+QyGcukjZk0ELfa/RtKrZMaq9i+yE1j0RcYeHGEH V+4RtLXDWPxnAymJMfcVpu0JZEZoxenwNXkmgyYKMQXGnN1Ls7NkOSx9TgW4IEazH0HS TOy4lNsQjFRd71dz5D/Ux8BGGU+UgNurAc7P2zcBMC8bJFwbS5pJWekOq461oc+DsRDd eh87WbfBiCTIu2NxwA+S3LoC7J0WxrnESI1Jt77XHjKjToAke3bka2tT28oXpFfiDYxk GFbg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=VEAekRrz/FSY4pk4QnV3m6H5QVjhz8BFDYr0EcpVw1E=; b=Ys0eRtOoanttAAbyRmgvUhOf1dORCJ4ngrpSeqCNx032O2sf9donmzsmKsq7Mr+8DM XCCc6mX69Ym93O/y+BrDgMmtx3el3HuV2XtZwmn99RQjftMhislhCjOrFcDiqtvA1Oml 1gSvizRsR6PZ5q8klKVo+obJM0LGBOSZw80l489N2/ajb/imc70xSTmOb1ILs7IqQ+jT ZMksD4Fl3D2ZG5DjkxAplMSmPN64E5hkq8G5+OI9xJ2wvSUjRBY6cExcH9e7mN3a0ZgN TD7lxngfeYTIe/+Voi8hWlkyULpIyC1VTV3dc6o5HylPaC+H1tNaPSyIDqzahM6kpFQi 0Mig== X-Gm-Message-State: AOAM532pXe8jSLR4TRE9B6g2mR2pkgs0eh6pz6GJ3pisaMTo/O7suh7l ZDPREWsBNf/2jc4QHYvD7WQ= X-Google-Smtp-Source: ABdhPJyWn7wVchQLELsEVq6TA/gUzEaBn19VUAXtFTYBInhQr0sSQqMx29HcpQwhBHqmmOM8Z+iT0g== X-Received: by 2002:a17:907:7baa:b0:6fe:b3dc:2378 with SMTP id ne42-20020a1709077baa00b006feb3dc2378mr30766036ejc.266.1653648395645; Fri, 27 May 2022 03:46:35 -0700 (PDT) Received: from gmail.com (563BA16F.dsl.pool.telekom.hu. [86.59.161.111]) by smtp.gmail.com with ESMTPSA id i20-20020a17090639d400b006fec1a73e48sm1320742eje.64.2022.05.27.03.46.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 May 2022 03:46:34 -0700 (PDT) Date: Fri, 27 May 2022 12:46:31 +0200 From: Ingo Molnar To: Peter Xu Subject: Re: [PATCH v3] mm: Avoid unnecessary page fault retires on shared memory types Message-ID: References: <20220524234531.1949-1-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220524234531.1949-1-peterx@redhat.com> X-BeenThere: openrisc@lists.librecores.org X-Mailman-Version: 2.1.26 Precedence: list List-Id: Discussion around the OpenRISC processor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: x86@kernel.org, Catalin Marinas , David Hildenbrand , Peter Zijlstra , Benjamin Herrenschmidt , Dave Hansen , linux-mips@vger.kernel.org, "James E . J . Bottomley" , linux-mm@kvack.org, Rich Felker , Paul Mackerras , "H . Peter Anvin" , sparclinux@vger.kernel.org, linux-ia64@vger.kernel.org, Alexander Gordeev , Will Deacon , linux-riscv@lists.infradead.org, Anton Ivanov , Jonas Bonn , linux-s390@vger.kernel.org, linux-snps-arc@lists.infradead.org, Yoshinori Sato , linux-xtensa@linux-xtensa.org, linux-hexagon@vger.kernel.org, Helge Deller , Alistair Popple , Hugh Dickins , Russell King , linux-csky@vger.kernel.org, linux-sh@vger.kernel.org, Ingo Molnar , linux-arm-kernel@lists.infradead.org, Vineet Gupta , Matt Turner , Christian Borntraeger , Andrea Arcangeli , Albert Ou , Vasily Gorbik , Brian Cain , Heiko Carstens , Johannes Weiner , linux-um@lists.infradead.org, Nicholas Piggin , Richard Weinberger , linux-m68k@lists.linux-m68k.org, openrisc@lists.librecores.org, Ivan Kokshaysky , Al Viro , Andy Lutomirski , Paul Walmsley , Thomas Gleixner , linux-alpha@vger.kernel.org, Andrew Morton , Vlastimil Babka , Richard Henderson , Chris Zankel , Michal Simek , Thomas Bogendoerfer , linux-parisc@vger.kernel.org, Max Filippov , linux-kernel@vger.kernel.org, Dinh Nguyen , Palmer Dabbelt , Sven Schnelle , Guo Ren , Michael Ellerman , Borislav Petkov , Johannes Berg , linuxppc-dev@lists.ozlabs.org, "David S . Miller" Errors-To: openrisc-bounces@lists.librecores.org Sender: "OpenRISC" * Peter Xu wrote: > This patch provides a ~12% perf boost on my aarch64 test VM with a simple > program sequentially dirtying 400MB shmem file being mmap()ed and these are > the time it needs: > > Before: 650.980 ms (+-1.94%) > After: 569.396 ms (+-1.38%) Nice! > arch/x86/mm/fault.c | 4 ++++ Reviewed-by: Ingo Molnar Minor comment typo: > + /* > + * We should do the same as VM_FAULT_RETRY, but let's not > + * return -EBUSY since that's not reflecting the reality on > + * what has happened - we've just fully completed a page > + * fault, with the mmap lock released. Use -EAGAIN to show > + * that we want to take the mmap lock _again_. > + */ s/reflecting the reality on what has happened /reflecting the reality of what has happened > ret = handle_mm_fault(vma, address, fault_flags, NULL); > + > + if (ret & VM_FAULT_COMPLETED) { > + /* > + * NOTE: it's a pity that we need to retake the lock here > + * to pair with the unlock() in the callers. Ideally we > + * could tell the callers so they do not need to unlock. > + */ > + mmap_read_lock(mm); > + *unlocked = true; > + return 0; Indeed that's a pity - I guess more performance could be gained here, especially in highly parallel threaded workloads? 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[86.59.161.111]) by smtp.gmail.com with ESMTPSA id i20-20020a17090639d400b006fec1a73e48sm1320742eje.64.2022.05.27.03.46.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 May 2022 03:46:34 -0700 (PDT) Date: Fri, 27 May 2022 12:46:31 +0200 From: Ingo Molnar To: Peter Xu Subject: Re: [PATCH v3] mm: Avoid unnecessary page fault retires on shared memory types Message-ID: References: <20220524234531.1949-1-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220524234531.1949-1-peterx@redhat.com> X-Mailman-Approved-At: Fri, 27 May 2022 21:29:50 +1000 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: x86@kernel.org, Catalin Marinas , David Hildenbrand , Peter Zijlstra , Dave Hansen , linux-mips@vger.kernel.org, "James E . J . 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Peter Anvin" , sparclinux@vger.kernel.org, linux-ia64@vger.kernel.org, Alexander Gordeev , Will Deacon , linux-riscv@lists.infradead.org, Anton Ivanov , Jonas Bonn , linux-s390@vger.kernel.org, linux-snps-arc@lists.infradead.org, Yoshinori Sato , linux-xtensa@linux-xtensa.org, linux-hexagon@vger.kernel.org, Helge Deller , Alistair Popple , Hugh Dickins , Russell King , linux-csky@vger.kernel.org, linux-sh@vger.ke rnel.org, Ingo Molnar , Geert Uytterhoeven , linux-arm-kernel@lists.infradead.org, Vineet Gupta , Stafford Horne , Matt Turner , Christian Borntraeger , Andrea Arcangeli , Albert Ou , Vasily Gorbik , Brian Cain , Heiko Carstens , Johannes Weiner , linux-um@lists.infradead.org, Nicholas Piggin , Stefan Kristiansson , Richard Weinberger , linux-m68k@lists.linux-m68k.org, openrisc@lists.librecores.org, Ivan Kokshaysky , Al Viro , Andy Lutomirski , Paul Walmsley , Thomas Gleixner , linux-alpha@vger.kernel.org, Andrew Morton , Vlastimil Bab ka , Richard Henderson , Chris Zankel , Michal Simek , Thomas Bogendoerfer , linux-parisc@vger.kernel.org, Max Filippov , linux-kernel@vger.kernel.org, Dinh Nguyen , Palmer Dabbelt , Sven Schnelle , Guo Ren , Borislav Petkov , Johannes Berg , linuxppc-dev@lists.ozlabs.org, "David S . Miller" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" * Peter Xu wrote: > This patch provides a ~12% perf boost on my aarch64 test VM with a simple > program sequentially dirtying 400MB shmem file being mmap()ed and these are > the time it needs: > > Before: 650.980 ms (+-1.94%) > After: 569.396 ms (+-1.38%) Nice! > arch/x86/mm/fault.c | 4 ++++ Reviewed-by: Ingo Molnar Minor comment typo: > + /* > + * We should do the same as VM_FAULT_RETRY, but let's not > + * return -EBUSY since that's not reflecting the reality on > + * what has happened - we've just fully completed a page > + * fault, with the mmap lock released. Use -EAGAIN to show > + * that we want to take the mmap lock _again_. > + */ s/reflecting the reality on what has happened /reflecting the reality of what has happened > ret = handle_mm_fault(vma, address, fault_flags, NULL); > + > + if (ret & VM_FAULT_COMPLETED) { > + /* > + * NOTE: it's a pity that we need to retake the lock here > + * to pair with the unlock() in the callers. Ideally we > + * could tell the callers so they do not need to unlock. > + */ > + mmap_read_lock(mm); > + *unlocked = true; > + return 0; Indeed that's a pity - I guess more performance could be gained here, especially in highly parallel threaded workloads? Thanks, Ingo