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, 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 08C1AC433DB for ; Fri, 22 Jan 2021 12:15:23 +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 8843923437 for ; Fri, 22 Jan 2021 12:15:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8843923437 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-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject: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=g9MBrmK2VGspBG2aMesFJ+OyFhYuOnclbdRWAQrHVl8=; b=IbLywH7p4FkrLIAeqv2MVe/nR p5YVDJUFeroQovbKeTCbujECOYk+jbmae6kV7NbwVeJHqTaSqekuaGVFEvINM076el6Hf6ArG5lFh eF8Ri456Ge3XThEp4Dw5ReDU60GbEnaxy1Q0Pyt0MIf/L2sfHaaZN01Se3guD/2lG00plq/vIxakR fErQHVhX9KAaXzdsLPpon3Ds1mdKgDTB/394hY9Nu3429SpixDH5UQD+kzn/XXLJrLw/y+j7HQoku S7ZHp5XqWAhXVxFEN6OgUavcDTwl+pBtcYcGOFoELFhy77D/Q3wzXXhiYbDNPjf3jNQtw8CByn3Cf hrDDPOEMg==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l2vJv-0007Ws-Ct; Fri, 22 Jan 2021 12:13:43 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1l2vJs-0007WV-Uf for linux-arm-kernel@lists.infradead.org; Fri, 22 Jan 2021 12:13:42 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id A5A7323437; Fri, 22 Jan 2021 12:13:37 +0000 (UTC) Date: Fri, 22 Jan 2021 12:13:35 +0000 From: Catalin Marinas To: Robin Murphy Subject: Re: [PATCH 0/1] mm: Optimizing hugepage zeroing in arm64 Message-ID: <20210122121334.GC8567@gaia> References: <20210121165153.17828-1-prathu.baronia@oneplus.com> <20210121174616.GA22740@willie-the-truck> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210122_071341_077370_B95453AD X-CRM114-Status: GOOD ( 20.78 ) 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 , Andrey Konovalov , Prathu Baronia , linux-kernel@vger.kernel.org, Prathu Baronia , chintan.pandya@oneplus.com, "glider@google.com" , Geert Uytterhoeven , Andrew Morton , Vincenzo Frascino , Will Deacon , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Jan 21, 2021 at 06:59:37PM +0000, Robin Murphy wrote: > 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. I thought the kmap_local stuff was supposed to fix this unnecessary preemption disabling on 64-bit architectures: https://lwn.net/Articles/836144/ I guess it's not there yet. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel