linux-kernel - Re: [PATCH BUGFIX/IMPROVEMENT V2 0/3] three bfq fixes restoring service guarantees with random sync writes in bg

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Date:   Mon, 4 Sep 2017 17:07:14 +0800
From:   Ming Lei <tom.leiming@...il.com>
To:     Mel Gorman <mgorman@...hsingularity.net>
Cc:     Paolo Valente <paolo.valente@...aro.org>,
        Jens Axboe <axboe@...nel.dk>,
        linux-block <linux-block@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        ulf.hansson@...aro.org, Mark Brown <broonie@...nel.org>,
        lee.tibbert@...il.com, oleksandr@...alenko.name
Subject: Re: [PATCH BUGFIX/IMPROVEMENT V2 0/3] three bfq fixes restoring
 service guarantees with random sync writes in bg

On Mon, Sep 4, 2017 at 4:14 PM, Mel Gorman <mgorman@...hsingularity.net> wrote:
> On Thu, Aug 31, 2017 at 03:42:57PM +0100, Mel Gorman wrote:
>> On Thu, Aug 31, 2017 at 08:46:28AM +0200, Paolo Valente wrote:
>> > [SECOND TAKE, with just the name of one of the tester fixed]
>> >
>> > Hi,
>> > while testing the read-write unfairness issues reported by Mel, I
>> > found BFQ failing to guarantee good responsiveness against heavy
>> > random sync writes in the background, i.e., multiple writers doing
>> > random writes and systematic fdatasync [1]. The failure was caused by
>> > three related bugs, because of which BFQ failed to guarantee to
>> > high-weight processes the expected fraction of the throughput.
>> >
>>
>> Queued on top of Ming's most recent series even though that's still a work
>> in progress. I should know in a few days how things stand.
>>
>
> The problems with parallel heavy writers seem to have disappeared with this
> series. There are still revisions taking place on Ming's to overall setting
> of legacy vs mq is still a work in progress but this series looks good.

Hi Mel and Paolo,

BTW, no actual functional change in V4.

Also could you guys provide one tested-by since looks you are using
it in your test?

Thanks,
Ming Lei