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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, 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 5C2F6C54FC9 for ; Tue, 21 Apr 2020 13:39:44 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1DE13206B9 for ; Tue, 21 Apr 2020 13:39:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="juTWv7Kw" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1DE13206B9 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id AEA988E0005; Tue, 21 Apr 2020 09:39:43 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A99E18E0003; Tue, 21 Apr 2020 09:39:43 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9AEBE8E0005; Tue, 21 Apr 2020 09:39:43 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0046.hostedemail.com [216.40.44.46]) by kanga.kvack.org (Postfix) with ESMTP id 83F3B8E0003 for ; Tue, 21 Apr 2020 09:39:43 -0400 (EDT) Received: from smtpin02.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 44112181AEF1D for ; Tue, 21 Apr 2020 13:39:43 +0000 (UTC) X-FDA: 76731969846.02.lead44_37baf5652413e X-HE-Tag: lead44_37baf5652413e X-Filterd-Recvd-Size: 2681 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf34.hostedemail.com (Postfix) with ESMTP for ; Tue, 21 Apr 2020 13:39:42 +0000 (UTC) Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B0553206A5; Tue, 21 Apr 2020 13:39:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587476382; bh=BFyClpGHfN1j05lnZlosvFziy3jefA8wth38Ms3XlL4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=juTWv7KwXyB8O0RNDBjgO3heRku/UG+T32eUcS2U/xymICY1pfREPOc+8zRZBTkWR MvZUNS8wj+JRM1U+Lguzxw0prKjbWp2kGTfMdR6QN+UZhBsxdOuXB7uXPsIwkOeoLF 5u0D3xH2o8hP6YPpFqPWU1t0mZ4bWS7DNM0bpUfE= Date: Tue, 21 Apr 2020 14:39:36 +0100 From: Will Deacon To: Vlastimil Babka Cc: Prathu Baronia , catalin.marinas@arm.com, alexander.duyck@gmail.com, chintan.pandya@oneplus.com, mhocko@suse.com, akpm@linux-foundation.org, linux-mm@kvack.org, gregkh@linuxfoundation.com, gthelen@google.com, jack@suse.cz, ken.lin@oneplus.com, gasine.xu@oneplus.com, ying.huang@intel.com, mark.rutland@arm.com Subject: Re: [PATCH v2] mm: Optimized hugepage zeroing & copying from user Message-ID: <20200421133935.GC17875@willie-the-truck> References: <20200414153829.GA15230@oneplus.com> <87r1wpzavo.fsf@yhuang-dev.intel.com> <20200419155856.dtwxomdkyujljdfi@oneplus.com> <87k12bt3ff.fsf@yhuang-dev.intel.com> <20200421093621.3fuptvf2qbyfzwfz@oneplus.com> <20200421100932.GC17256@willie-the-truck> <02d5daa8-ee7b-7d2d-6753-5191a7d761b9@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <02d5daa8-ee7b-7d2d-6753-5191a7d761b9@suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) 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 Tue, Apr 21, 2020 at 02:48:04PM +0200, Vlastimil Babka wrote: > On 4/21/20 2:47 PM, Vlastimil Babka wrote: > > > > It was suspected that current Intel can prefetch forward and backwards, and the > > tested ARM64 microarchitecture only backwards, can it be true? The current code > > Oops, tested ARM64 microarchitecture I meant "only forwards". I'd be surprised if that's the case, but it could be that there's an erratum workaround in play which hampers the prefetch behaviour. We generally try not to assume too much about the prefetcher on arm64 because they're not well documented and vary wildly between different micro-architectures. Will