linux-kernel - Re: [PATCHSET block/for-next] IO cost model based work-conserving porportional controller

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Message-ID: <20190820151903.GH2263813@devbig004.ftw2.facebook.com>
Date:   Tue, 20 Aug 2019 08:19:03 -0700
From:   Tejun Heo <tj@...nel.org>
To:     Paolo Valente <paolo.valente@...aro.org>
Cc:     Jens Axboe <axboe@...nel.dk>, newella@...com, clm@...com,
        Josef Bacik <josef@...icpanda.com>, dennisz@...com,
        Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-block <linux-block@...r.kernel.org>, kernel-team@...com,
        cgroups@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
        kafai@...com, songliubraving@...com, yhs@...com,
        bpf@...r.kernel.org
Subject: Re: [PATCHSET block/for-next] IO cost model based work-conserving
 porportional controller

Hello, Paolo.

On Tue, Aug 20, 2019 at 05:04:25PM +0200, Paolo Valente wrote:
> and makes one fio instance generate I/O for each group.  The bandwidth
> reported above is that reported by the fio instance emulating the
> target client.
> 
> Am I missing something?

If you didn't configure QoS targets, the controller is using device
qdepth saturation as the sole guidance in determining whether the
device needs throttling.  Please try configuring the target latencies.
The bandwidth you see for single stream of rand ios should have direct
correlation with how the latency targets are configured.  The head
letter for the patchset has some examples.

Thanks.

-- 
tejun