From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH v2 3/3] libata: use blk taging Date: Thu, 15 Jan 2015 10:02:09 -0500 Message-ID: <20150115150209.GA25903@htj.dyndns.org> References: <20150109181529.GA1301458@devbig257.prn2.facebook.com> <20150109214307.GE2785@htj.dyndns.org> <20150109215919.GA1826518@devbig257.prn2.facebook.com> <20150109221209.GA1851286@devbig257.prn2.facebook.com> <20150114163006.GA3575264@devbig257.prn2.facebook.com> <20150114171328.GA3636164@devbig257.prn2.facebook.com> <20150115092836.GA14051@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-qa0-f41.google.com ([209.85.216.41]:52566 "EHLO mail-qa0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932081AbbAOPCO (ORCPT ); Thu, 15 Jan 2015 10:02:14 -0500 Received: by mail-qa0-f41.google.com with SMTP id bm13so11425827qab.0 for ; Thu, 15 Jan 2015 07:02:13 -0800 (PST) Content-Disposition: inline In-Reply-To: <20150115092836.GA14051@infradead.org> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Christoph Hellwig Cc: Dan Williams , Shaohua Li , IDE/ATA development list , Kernel-team@fb.com, Jens Axboe Hello, On Thu, Jan 15, 2015 at 01:28:36AM -0800, Christoph Hellwig wrote: > libata on the other hand at the moment assigns it's own tags, > which are only stored in struct ata_queued_cmd, but never in the > request. libata assigns tags per ata_host. Each ata_host Per ata_port. > might have multiple ports, which each get their own Scsi_Host > allocated. > > Given that ATA NCQ has a fairly low queue depth I assume we want > to stick to assigning ATA tags per-device, but due to the host > per device scheme libata that even works using scsi-mq. (Q: how do tags > work when port mulipliers are involved?) It's still per-port. The same number of tags are shared among all devices attached via PMs. Thanks. -- tejun