linux-kernel - Re: CFQ idling kills I/O performance on ext4 with blkio cgroup controller

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Message-ID: <7c5e9d11-4a3d-7df4-c1e6-7c95919522ab@csail.mit.edu>
Date:   Tue, 11 Jun 2019 15:34:48 -0700
From:   "Srivatsa S. Bhat" <srivatsa@...il.mit.edu>
To:     Paolo Valente <paolo.valente@...aro.org>
Cc:     linux-fsdevel@...r.kernel.org,
        linux-block <linux-block@...r.kernel.org>,
        linux-ext4@...r.kernel.org, cgroups@...r.kernel.org,
        kernel list <linux-kernel@...r.kernel.org>,
        Jens Axboe <axboe@...nel.dk>, Jan Kara <jack@...e.cz>,
        Jeff Moyer <jmoyer@...hat.com>, Theodore Ts'o <tytso@....edu>,
        amakhalov@...are.com, anishs@...are.com, srivatsab@...are.com,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: Re: CFQ idling kills I/O performance on ext4 with blkio cgroup
 controller

On 6/2/19 12:04 AM, Srivatsa S. Bhat wrote:
> On 5/30/19 3:45 AM, Paolo Valente wrote:
>>
[...]
>> At any rate, since you pointed out that you are interested in
>> out-of-the-box performance, let me complete the context: in case
>> low_latency is left set, one gets, in return for this 12% loss,
>> a) at least 1000% higher responsiveness, e.g., 1000% lower start-up
>> times of applications under load [1];
>> b) 500-1000% higher throughput in multi-client server workloads, as I
>> already pointed out [2].
>>
> 
> I'm very happy that you could solve the problem without having to
> compromise on any of the performance characteristics/features of BFQ!
> 
> 
>> I'm going to prepare complete patches.  In addition, if ok for you,
>> I'll report these results on the bug you created.  Then I guess we can
>> close it.
>>
> 
> Sounds great!
>

Hi Paolo,

Hope you are doing great!

I was wondering if you got a chance to post these patches to LKML for
review and inclusion... (No hurry, of course!)

Also, since your fixes address the performance issues in BFQ, do you
have any thoughts on whether they can be adapted to CFQ as well, to
benefit the older stable kernels that still support CFQ?

Thank you!

Regards,
Srivatsa
VMware Photon OS