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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 5B936C47255 for ; Mon, 11 May 2020 17:02:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 390F220722 for ; Mon, 11 May 2020 17:02:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="c3U4wuy0" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730797AbgEKRCe (ORCPT ); Mon, 11 May 2020 13:02:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35182 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730066AbgEKRCd (ORCPT ); Mon, 11 May 2020 13:02:33 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C1A3FC061A0C; Mon, 11 May 2020 10:02:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Hy07Ws6ek9XvAGJzrptGNVmN+sgjs2KIi/oCXeVqo9E=; b=c3U4wuy0ttwAXhwRpOyq47EcOS R6BOJ5hTKfV9cW8xiSDAIUq0HXFikJF4ynwAq2vypi9olfTDqkb8ufZMT5CdzATb4pwn0Qk9J7SPT 7BH7P/aQYee+IokeeKf35kRg9Wmd7JuXGNX9J+h1igQwb86BgPLoijcEkBNddzK2nN5fn85jy8Vyt +SJyixpxAMl+sc5RquVfvSaqZYi5y8y8ukaTlE7TPPhj7mPTbxr6gjm9iNY3oHOE346HsINHrmgF9 px9am0ZSFLIKDsibuJ5+DooCPkne6W5heGMWIZYD5BJEurvKKcpF722OXItxoehCgllZpODKHto9m mF7LkNEg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jYBol-0002Do-R6; Mon, 11 May 2020 17:02:16 +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 DC87C304123; Mon, 11 May 2020 19:02:12 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id CBF5329D8226A; Mon, 11 May 2020 19:02:12 +0200 (CEST) Date: Mon, 11 May 2020 19:02:12 +0200 From: Peter Zijlstra To: Matthew Wilcox Cc: Joerg Roedel , Joerg Roedel , x86@kernel.org, hpa@zytor.com, Dave Hansen , Andy Lutomirski , rjw@rjwysocki.net, Arnd Bergmann , Andrew Morton , Steven Rostedt , Vlastimil Babka , Michal Hocko , linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC PATCH 0/7] mm: Get rid of vmalloc_sync_(un)mappings() Message-ID: <20200511170212.GI2957@hirez.programming.kicks-ass.net> References: <20200508144043.13893-1-joro@8bytes.org> <20200508192000.GB2957@hirez.programming.kicks-ass.net> <20200508213407.GT8135@suse.de> <20200509092516.GC2957@hirez.programming.kicks-ass.net> <20200510011157.GU16070@bombadil.infradead.org> <20200511073134.GD2957@hirez.programming.kicks-ass.net> <20200511155204.GW16070@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200511155204.GW16070@bombadil.infradead.org> Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On Mon, May 11, 2020 at 08:52:04AM -0700, Matthew Wilcox wrote: > On Mon, May 11, 2020 at 09:31:34AM +0200, Peter Zijlstra wrote: > > On Sat, May 09, 2020 at 06:11:57PM -0700, Matthew Wilcox wrote: > > > Iterating an XArray (whether the entire thing > > > or with marks) is RCU-safe and faster than iterating a linked list, > > > so this should solve the problem? > > > > It can hardly be faster if you want all elements -- which is I think the > > case here. We only call into this if we change an entry, and then we > > need to propagate that change to all. > > Of course it can be faster. Iterating an array is faster than iterating > a linked list because caches. While an XArray is a segmented array > (so slower than a plain array), it's plainly going to be faster than > iterating a linked list. Fair enough, mostly also because the actual work (setting a single PTE) doesn't dominate in this case.