From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH v6 0/3] Enabling ATA Command Priorities Date: Wed, 19 Oct 2016 14:38:45 -0400 Message-ID: <20161019183845.GL18532@htj.duckdns.org> References: <1476728850-2309-1-git-send-email-adam.manzanares@hgst.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1476728850-2309-1-git-send-email-adam.manzanares@hgst.com> Sender: linux-kernel-owner@vger.kernel.org To: Adam Manzanares Cc: axboe@kernel.dk, dan.j.williams@intel.com, hare@suse.de, martin.petersen@oracle.com, mchristi@redhat.com, toshi.kani@hpe.com, ming.lei@canonical.com, sathya.prakash@broadcom.com, chaitra.basappa@broadcom.com, suganath-prabu.subramani@broadcom.com, linux-block@vger.kernel.org, linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org, MPT-FusionLinux.pdl@broadcom.com, linux-scsi@vger.kernel.org List-Id: linux-ide@vger.kernel.org On Mon, Oct 17, 2016 at 11:27:27AM -0700, Adam Manzanares wrote: > This patch builds ATA commands with high priority if the iocontext of a process > is set to real time. The goal of the patch is to improve tail latencies of > workloads that use higher queue depths. This requires setting the iocontext > ioprio on the request when it is initialized > > This patch has been tested with an Ultrastar HE8 HDD and cuts the > the p99.99 tail latency of foreground IO from 2s down to 72ms when > using the deadline scheduler. This patch works independently of the > scheduler so it can be used with all of the currently available > request based schedulers. > > Foreground IO, for the previously described results, is an async fio job > submitting 4K read requests at a QD of 1 to the HDD. The foreground IO is set > with the iopriority class of real time. The background workload is another fio > job submitting read requests at a QD of 32 to the same HDD with default > iopriority. > > This feature is enabled for ATA devices by setting the ata ncq_prio_on device > attribute to 1. An ATA device is also checked to see if the device supports per > command priority. Applied 1-3 to libata/for-4.10 w/ some modifications. Thanks. -- tejun