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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 2E4F6C43441 for ; Thu, 22 Nov 2018 15:19:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E51F920824 for ; Thu, 22 Nov 2018 15:19:54 +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="F5M5491b" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E51F920824 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2437621AbeKWB7l (ORCPT ); Thu, 22 Nov 2018 20:59:41 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:41922 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730517AbeKWB7k (ORCPT ); Thu, 22 Nov 2018 20:59:40 -0500 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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=4PmuZ+BvucwdqnJ7cMjJm7ggtSvmkj6s3xiw/bvz428=; b=F5M5491bpKB4z/QaPUULu0BPp ScSIEfR2o7ZWXddMLAfJVvpcyd/VtOcd73HMocLqTfx3pexUPHd5dqggnQcV6m7qjTweoqQDXzxfJ OLqFSdKfiL1vDE+S85hdTDmepYc2rOkzm7CoOvSFMy6h69xO9VIBQScUGVT8QoK6wD/Jp+M6Aboe8 /vGpjQW6+s+2HMWpRY0r6yzsyVWBD3a2CBzFN/WLMBB9TLw1u47lD+UJQwxoJiWVm+HaO7ZSy0cSa fuJzeqq1VdnaDbv6PB0Tmb86FLgEucD+gZFHwhfbdazPHYcWhbIiq7Ot85lVD3C9SXNQkc7axVDVb FJnJE6GFA==; Received: from hch by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1gPqlZ-0000kx-9D; Thu, 22 Nov 2018 15:19:41 +0000 Date: Thu, 22 Nov 2018 07:19:41 -0800 From: Christoph Hellwig To: Matthew Wilcox Cc: Christoph Hellwig , Robin Murphy , Michal Hocko , Will Deacon , Levin Alexander , linux-mm@kvack.org, Christopher Lameter , Nicolas Boichat , Huaisheng Ye , David Rientjes , yingjoe.chen@mediatek.com, Vlastimil Babka , Tomasz Figa , Mike Rapoport , Matthias Brugger , Joonsoo Kim , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Pekka Enberg , iommu@lists.linux-foundation.org, Andrew Morton , Mel Gorman Subject: Re: [PATCH v2 0/3] iommu/io-pgtable-arm-v7s: Use DMA32 zone for page tables Message-ID: <20181122151941.GA2681@infradead.org> References: <20181111090341.120786-1-drinkcat@chromium.org> <0100016737801f14-84f1265d-4577-4dcf-ad57-90dbc8e0a78f-000000@email.amazonses.com> <20181121213853.GL3065@bombadil.infradead.org> <20181122023558.GO3065@bombadil.infradead.org> <20181122082602.GB2049@infradead.org> <20181122151632.GP3065@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181122151632.GP3065@bombadil.infradead.org> User-Agent: Mutt/1.9.2 (2017-12-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 22, 2018 at 07:16:32AM -0800, Matthew Wilcox wrote: > Yes, your allocations from the page_frag allocator have to have similar > lifetimes. I thought that would be ideal for XFS though; as I understood > the problem, these were per-IO allocations, and IOs to the same filesystem > tend to take roughly the same amount of time. Sure, in an error case, > some IOs will take a long time before timing out, but it should be OK > to have pages unavailable during that time in these rare situations. > What am I missing? No, thee are allocations for meatada buffers, which can stay around for a long time. Worse still that depends on usage, so one buffer allocated from ma page might basically stay around forever, while another one might get reclaimed very quickly.