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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 4A1B0C433E6 for ; Thu, 25 Feb 2021 10:00:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E713464ED3 for ; Thu, 25 Feb 2021 10:00:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234567AbhBYKAg (ORCPT ); Thu, 25 Feb 2021 05:00:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51424 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235541AbhBYJzx (ORCPT ); Thu, 25 Feb 2021 04:55:53 -0500 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DCBABC061574 for ; Thu, 25 Feb 2021 01:55:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Transfer-Encoding: Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description; bh=ILy7hOxPlcatByP7X1y13wdKQwSGNRl/iT8aWHTE2qw=; b=ZqxKzT7/r1NE04sirOzcr608B/ R395iSU0IRoUkHWEpfHW25yW2KdYeGsZKPTLPEdgFY7LQv6Enquz76tVioN2ipKI4aRH2MaBCyrbB QmbDmbkMdjh9UE5bL7mBkmJ4UFTFFJMd6Ca53jgr7FTVPqeg20DJdO53sw97uLsiyjOn2L9kwonYx s+oJRl2s3vjcgKC6AhV1oy56xcGmVXDXfiawqCsMaIhWEyahIq7y9jNHmstooc82BYXRB1ih/e6hr 8gjPX/lMonfStCVM1GotQdjVure9uouOQhHu+MRtZp+NE63ljdhVpoqGziDOA3bDPtSofYNvg7NLa z0W34GxA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1lFDMM-0000C3-H2; Thu, 25 Feb 2021 09:55:02 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 8E33A300DB4; Thu, 25 Feb 2021 10:55:00 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 7AEB0201C2FE0; Thu, 25 Feb 2021 10:55:00 +0100 (CET) Date: Thu, 25 Feb 2021 10:55:00 +0100 From: Peter Zijlstra To: Nadav Amit Cc: Linux-MM , LKML , Hugh Dickins , Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Sean Christopherson , Andrew Morton , x86@kernel.org Subject: Re: [RFC 0/6] x86: prefetch_page() vDSO call Message-ID: References: <20210225072910.2811795-1-namit@vmware.com> <64538CCF-AD11-43C2-9632-E054301F9E6D@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 25, 2021 at 01:32:56AM -0800, Nadav Amit wrote: > > On Feb 25, 2021, at 12:52 AM, Nadav Amit wrote: > > Can you give me a reference to the =E2=80=9Cremoving explicit prefetch = =66rom some > > parts of the kernel=E2=80=9D? 75d65a425c01 ("hlist: remove software prefetching in hlist iterators") e66eed651fd1 ("list: remove prefetching from regular list iterators") > Oh. I get it - you mean we remove we remove the use of explicit memory > prefetch from the kernel code. Well, I don=E2=80=99t think it is really r= elated, > but yes, performance numbers are needed. Right, so my main worry was that use of the prefetch instruction actually hurt performance once the hardware prefetchers got smart enough, this being a very similar construct (just on a different level of the stack) should be careful not to suffer the same fate.