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Subject: Re: [PATCH BUGFIX/IMPROVEMENT V2 0/3] three bfq fixes restoring service guarantees with random sync writes in bg
From: Paolo Valente <paolo.valente@linaro.org>
In-Reply-To: <20170904081451.swq52kn2x24guphz@techsingularity.net>
Date: Mon, 4 Sep 2017 10:55:13 +0200
Cc: Jens Axboe <axboe@kernel.dk>,
        linux-block <linux-block@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Ulf Hansson <ulf.hansson@linaro.org>, broonie@kernel.org,
        lee.tibbert@gmail.com, oleksandr@natalenko.name
Message-Id: <4532CA63-C71A-41E9-AE91-D685F3692475@linaro.org>
References: <20170831064631.2223-1-paolo.valente@linaro.org> <20170831144257.oa5nm6vzihpam6kw@techsingularity.net> <20170904081451.swq52kn2x24guphz@techsingularity.net>
To: Mel Gorman <mgorman@techsingularity.net>
Sender: linux-kernel-owner@vger.kernel.org
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> Il giorno 04 set 2017, alle ore 10:14, Mel Gorman <mgorman@techsingularity.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