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[134.134.136.31]) by mx.google.com with ESMTPS id s6si11530483plq.160.2019.02.20.08.39.24 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 20 Feb 2019 08:39:24 -0800 (PST) Received-SPF: pass (google.com: domain of keith.busch@intel.com designates 134.134.136.31 as permitted sender) client-ip=134.134.136.31; Authentication-Results: mx.google.com; spf=pass (google.com: domain of keith.busch@intel.com designates 134.134.136.31 as permitted sender) smtp.mailfrom=keith.busch@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 20 Feb 2019 08:39:23 -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) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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.