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=-2.5 required=3.0 tests=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 C06F2C43381 for ; Wed, 20 Feb 2019 16:39:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8BE282147A for ; Wed, 20 Feb 2019 16:39:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726003AbfBTQjZ (ORCPT ); Wed, 20 Feb 2019 11:39:25 -0500 Received: from mga18.intel.com ([134.134.136.126]:37610 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725798AbfBTQjY (ORCPT ); Wed, 20 Feb 2019 11:39:24 -0500 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 20 Feb 2019 08:39:24 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,391,1544515200"; d="scan'208";a="125905373" Received: from unknown (HELO localhost.localdomain) ([10.232.112.69]) by fmsmga008.fm.intel.com with ESMTP; 20 Feb 2019 08:39:22 -0800 Date: Wed, 20 Feb 2019 09:39:22 -0700 From: Keith Busch To: Matthew Wilcox Cc: William Kucharski , lsf-pc@lists.linux-foundation.org, Linux-MM , linux-fsdevel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org Subject: Re: Read-only Mapping of Program Text using Large THP Pages Message-ID: <20190220163921.GA4451@localhost.localdomain> References: <379F21DD-006F-4E33-9BD5-F81F9BA75C10@oracle.com> <20190220134454.GF12668@bombadil.infradead.org> <07B3B085-C844-4A13-96B1-3DB0F1AF26F5@oracle.com> <20190220144345.GG12668@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190220144345.GG12668@bombadil.infradead.org> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Wed, Feb 20, 2019 at 06:43:46AM -0800, Matthew Wilcox wrote: > What NVMe doesn't have is a way for the host to tell the controller > "Here's a 2MB sized I/O; bytes 40960 to 45056 are most important to > me; please give me a completion event once those bytes are valid and > then another completion event once the entire I/O is finished". > > I have no idea if hardware designers would be interested in adding that > kind of complexity, but this is why we also have I/O people at the same > meeting, so we can get these kinds of whole-stack discussions going. We have two unused PRP bits, so I guess there's room to define something like a "me first" flag. I am skeptical we'd get committee approval for that or partial completion events, though. I think the host should just split the more important part of the transfer into a separate command. The only hardware support we have to prioritize that command ahead of others is with weighted priority queues, but we're missing driver support for that at the moment.