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:   Thu, 31 Aug 2017 19:06:06 +0200
From:   Mike Galbraith <efault@....de>
To:     Mel Gorman <mgorman@...hsingularity.net>,
        Paolo Valente <paolo.valente@...aro.org>
Cc:     Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, 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

On Thu, 2017-08-31 at 15:42 +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.

It seems to have cured an interactivity issue I regularly meet during
kbuild final link/depmod phase of fat kernel kbuild, especially bad
with evolution mail usage during that on spinning rust.  Can't really
say for sure given this is not based on measurement.

	-Mike