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=-5.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 4598FC433E0 for ; Thu, 21 Jan 2021 19:01:14 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 02D8423A5D for ; Thu, 21 Jan 2021 19:01:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 02D8423A5D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=A/sG+rfaQ26WW6tAd7VRn4QSCa5gZnDe7gIpe+FPqVE=; b=g/XnNwk5bPJT5Xom5Sg2u4Fhr MbED/REdTi4EvkqLrYT+CEuzRfWuSq8idomzh/W2WVytRLHgtam7i1VApvzV3Fk2KYdqpw52uG9Ro hK7RszztD8MyNjsNP5kKkOzgKM6O/GsVeb6GEPBesGl/tjZj3OocjnKZR5duRXQxG0foAUjCUa2hh qKHALBHj2jkG6Fr+bLlgfZPQA8nyNS9ldVOCo0hxVU7aDxoW8Py7mpnKNY5Hm0/MH0aSu3i0Czckc TS/6ofdO14Y2lpdv7etYGLJYlqdKOQkjgtqzpxZU5aQCrkb5Q0pD3+VFs3lUWHlkQj2z6asyuYKCE ew/WvcuQQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l2fBJ-0005Sq-BJ; Thu, 21 Jan 2021 18:59:45 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l2fBG-0005Rx-G3 for linux-arm-kernel@lists.infradead.org; Thu, 21 Jan 2021 18:59:43 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id DBD39139F; Thu, 21 Jan 2021 10:59:40 -0800 (PST) Received: from [10.57.39.58] (unknown [10.57.39.58]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D91463F66E; Thu, 21 Jan 2021 10:59:38 -0800 (PST) Subject: Re: [PATCH 0/1] mm: Optimizing hugepage zeroing in arm64 To: Will Deacon , Prathu Baronia References: <20210121165153.17828-1-prathu.baronia@oneplus.com> <20210121174616.GA22740@willie-the-truck> From: Robin Murphy Message-ID: Date: Thu, 21 Jan 2021 18:59:37 +0000 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: <20210121174616.GA22740@willie-the-truck> Content-Language: en-GB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210121_135942_585101_CED00CAF X-CRM114-Status: GOOD ( 16.65 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Anshuman Khandual , Catalin Marinas , Prathu Baronia , linux-kernel@vger.kernel.org, chintan.pandya@oneplus.com, "glider@google.com" , Andrey Konovalov , Geert Uytterhoeven , Andrew Morton , Vincenzo Frascino , linux-arm-kernel@lists.infradead.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2021-01-21 17:46, Will Deacon wrote: > On Thu, Jan 21, 2021 at 10:21:50PM +0530, Prathu Baronia wrote: >> This patch removes the unnecessary kmap calls in the hugepage zeroing path and >> improves the timing by 62%. >> >> I had proposed a similar change in Apr-May'20 timeframe in memory.c where I >> proposed to clear out a hugepage by directly calling a memset over the whole >> hugepage but got the opposition that the change was not architecturally neutral. >> >> Upon revisiting this now I see significant improvement by removing around 2k >> barrier calls from the zeroing path. So hereby I propose an arm64 specific >> definition of clear_user_highpage(). > > Given that barrier() is purely a thing for the compiler, wouldn't the same > change yield a benefit on any other architecture without HIGHMEM? In which > case, I think this sort of change belongs in the core code if it's actually > worthwhile. I would have thought it's more the constant manipulation of the preempt and pagefault counts, rather than the compiler barriers between them, that has the impact. Either way, if arm64 doesn't need to be atomic WRT preemption when clearing parts of hugepages then I also can't imagine that anyone else (at least for !HIGHMEM) would either. Robin. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel