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 10:55:13 +0200
From:   Paolo Valente <paolo.valente@...aro.org>
To:     Mel Gorman <mgorman@...hsingularity.net>
Cc:     Jens Axboe <axboe@...nel.dk>,
        linux-block <linux-block@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>, 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


> Il giorno 04 set 2017, alle ore 10:14, Mel Gorman <mgorman@...hsingularity.net> ha scritto:
> 
> 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.
> 

Great news!

Thanks for testing,
Paolo

> Thanks.
> 
> -- 
> Mel Gorman
> SUSE Labs