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 -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
