linux-kernel - Re: [PATCH v7 0/4] Enabling ATA Command Priorities

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Date:   Tue, 6 Dec 2016 13:37:33 -0500
From:   Tejun Heo <tj@...nel.org>
To:     Adam Manzanares <adam.manzanares@...t.com>
Cc:     axboe@...nel.dk, hare@...e.de, mchristi@...hat.com,
        dan.j.williams@...el.com, martin.petersen@...cle.com,
        toshi.kani@....com, damien.lemoal@...t.com, ming.lei@...onical.com,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-ide@...r.kernel.org,
        Adam Manzanares <adam.manzanares@....com>
Subject: Re: [PATCH v7 0/4] Enabling ATA Command Priorities

Adam,

On Tue, Dec 06, 2016 at 09:18:01AM -0800, Adam Manzanares wrote:
> From: Adam Manzanares <adam.manzanares@....com>
> 
> 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_enable 
> device attribute to 1. An ATA device is also checked to see if the device 
> supports per command priority.
> 
> v7:
>  - Run ncq prio support check when sysfs variable set (zero day bug fix)
>  - Fixes from TJ merged in
>  - Merge fix for linux-next incorporated

The previous version has already been merged into libata/for-4.10.
Can you please send me an incremental patch on top of it?  The tree
can be fetched from

 git://git.kernel.org/pub/scm/linux/kernel/git/tj/libata.git for-4.10

Thanks.

-- 
tejun