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=-2.1 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 7FA9AC28CF8 for ; Sat, 13 Oct 2018 16:48:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 297A92077C for ; Sat, 13 Oct 2018 16:48:03 +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="Fnb73Eo1" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 297A92077C 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 S1726771AbeJNAZk (ORCPT ); Sat, 13 Oct 2018 20:25:40 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:43354 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726329AbeJNAZk (ORCPT ); Sat, 13 Oct 2018 20:25:40 -0400 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=5JTAhWThjAfobE+w/amOQSt4mRL4A8wfY378mriehps=; b=Fnb73Eo1jtSEVWcBDa3on5oAe XuBE0osk8cPwu1N0cGXHBb4fKGxnOhoyg+VqH1oijuIR9x3+qK5xDUHBcaOdLotOiznzP+xvVXprK HWkwtbaK6SNsiC/XGLPcDb7V3BZ+rw4xKtMPXV81MQWK7w/MJTpfD0MhPwk8lSa43cA1+XqO1Qbcd LZOiPA51JxoHxtM129XQuSzNjgsBlXUJ02nWiWR2j1ictuUYQEMUch1NG4Y/vAScrFcLqJIa8EGOf Gwt+gai4Z2ouhBGsJ9+od4JhaLJ3USzKpY8/9VlGr26NLaq5i9m1xla7G8+v7x7C/G1LdXpTAR90/ dCD1W4TSA==; Received: from hch by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1gBN4n-0001qf-Cd; Sat, 13 Oct 2018 16:47:41 +0000 Date: Sat, 13 Oct 2018 09:47:41 -0700 From: Christoph Hellwig To: John Hubbard Cc: Dave Chinner , Matthew Wilcox , Michal Hocko , Christopher Lameter , Jason Gunthorpe , Dan Williams , Jan Kara , linux-mm@kvack.org, Andrew Morton , LKML , linux-rdma , linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 4/6] mm: introduce page->dma_pinned_flags, _count Message-ID: <20181013164740.GA6593@infradead.org> References: <20181012060014.10242-1-jhubbard@nvidia.com> <20181012060014.10242-5-jhubbard@nvidia.com> <20181013035516.GA18822@dastard> <7c2e3b54-0b1d-6726-a508-804ef8620cfd@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7c2e3b54-0b1d-6726-a508-804ef8620cfd@nvidia.com> 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 Sat, Oct 13, 2018 at 12:34:12AM -0700, John Hubbard wrote: > In patch 6/6, pin_page_for_dma(), which is called at the end of get_user_pages(), > unceremoniously rips the pages out of the LRU, as a prerequisite to using > either of the page->dma_pinned_* fields. > > The idea is that LRU is not especially useful for this situation anyway, > so we'll just make it one or the other: either a page is dma-pinned, and > just hanging out doing RDMA most likely (and LRU is less meaningful during that > time), or it's possibly on an LRU list. Have you done any benchmarking what this does to direct I/O performance, especially for small I/O directly to a (fast) block device?