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SubjectRe: [PATCH V2 00/22] Replace the CFQ I/O Scheduler with BFQ
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Il giorno 05/set/2016, alle ore 17:56, Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com> ha scritto:

>
> Hi,
>
> On Thursday, September 01, 2016 10:39:46 AM Linus Walleij wrote:
>> On Thu, Sep 1, 2016 at 12:09 AM, Mark Brown <broonie@kernel.org> wrote:
>>
>>> - Do some benchmarks on the current status of the various branches on
>>> relevant hardware (including trying to convert some of these slower
>>> devices to blk-mq and seeing what happens). Linus has been working
>>> on this already in the context of MMC.
>>
>> I'm trying to do a patch switching MMC to use blk-mq, so I can
>> benchmark performance before/after this.
>>
>> While we expect mq to perform worse on single-hardware-queue
>> devices like these, we don't know until we tried, so I'm trying.
>
> I did this (switched MMC to blk-mq) some time ago. Patches are
> extremely ugly and hacky (basically the whole MMC block layer
> glue code needs to be re-done) so I'm rather reluctant to
> sharing them yet (to be honest I would like to rewrite them
> completely before posting).
>
> I only did linear read tests (using dd) so far and results that
> I got were mixed (BTW the hardware I'm doing this work on is
> Odroid-XU3). Pure block performance under maximum CPU frequency
> was slightly worse (5-12%) but the CPU consumption was reduced so
> when CPU was scaled down manually (or ondemand CPUfreq governor
> was used) blk-mq mode results were better then vanilla ones (up
> to 10% when CPU was scaled down to minimum frequency and even
> up to 50% when using ondemand governor - this finding is very
> interesting and needs to be investigated further).
>

IMO, another important figure of merit is application- and
system-level latency (e.g., application/system responsiveness or frame
drop rate with audio/video playback/streaming, while the device
happens to be busy with furhter I/O). Scripts to measure it can be
found, e.g., here [1] for desktop systems. If I can, I'm willing to
help in any respect.

Thanks,
Paolo

[1] https://github.com/Algodev-github/S

> Best regards,
> --
> Bartlomiej Zolnierkiewicz
> Samsung R&D Institute Poland
> Samsung Electronics
>
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