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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Message-ID: <da37f9a6-4954-3e70-f807-3b3daa7d9dd3@kernel.dk>
Date:   Thu, 31 Aug 2017 08:21:00 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Paolo Valente <paolo.valente@...aro.org>
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        ulf.hansson@...aro.org, broonie@...nel.org,
        mgorman@...hsingularity.net, 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 08/31/2017 12:46 AM, 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.
> 
> The three patches in this series fix these bugs. These fixes restore
> the usual BFQ service guarantees (and thus optimal responsiveness
> too), against the above background workload and, probably, against
> other similar workloads.

Applied for 4.14, thanks Paolo.

-- 
Jens Axboe