Messages in this thread |  | | Date | Wed, 19 Oct 2016 14:38:45 -0400 | From | Tejun Heo <> | Subject | Re: [PATCH v6 0/3] Enabling ATA Command Priorities |
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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
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