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 720EAC54E8E for ; Mon, 11 May 2020 15:52:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 42CFD20714 for ; Mon, 11 May 2020 15:52:16 +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="Q3uhuAi8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730519AbgEKPwO (ORCPT ); Mon, 11 May 2020 11:52:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52462 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1726687AbgEKPwO (ORCPT ); Mon, 11 May 2020 11:52:14 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 27B52C061A0C; Mon, 11 May 2020 08:52:14 -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=fgR2V/CO/9l3sT2m4IZfICSNwcHm5fI2cusmiGpz5bc=; b=Q3uhuAi8Znj5rCKf4UbH4yK66i R5rhxZT8aqzxuwdJ5y1oEivI3AsYvThrlFC3Q5WXrTvn/fRFQqzGrkJfk5ODEfG/zzW7+0cPqC8/r dbBWA2t2lHXCYO1njHg/KronsAe3pDXSvfJNx3h1AHe34N3ok2U8uiLP3mYk8tJDMJByKnWsMDcaf OdrcSV1SJGDHsSjb89RfXrrrnymtdouseL/A0QLzCOHfVMzLjt/sBWBMIV3gU0LjYvc3Zj+anqTCK XnV+TtcYan0RNagJ3Nskkv8wqmfAOFv7V35uYN9fRfCd00/N1aHqzLBnnC7lo9s5nvByBOntGcLbs I7F7ftnQ==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jYAiq-0003Lw-Nh; Mon, 11 May 2020 15:52:04 +0000 Date: Mon, 11 May 2020 08:52:04 -0700 From: Matthew Wilcox To: Peter Zijlstra 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: <20200511155204.GW16070@bombadil.infradead.org> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200511073134.GD2957@hirez.programming.kicks-ass.net> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.