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

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Date:   Thu, 13 Jun 2019 12:13:05 -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 6/12/19 10:46 PM, Paolo Valente wrote:
> 
>> Il giorno 12 giu 2019, alle ore 00:34, Srivatsa S. Bhat <srivatsa@...il.mit.edu> ha scritto:
>>
[...]
>>
>> Hi Paolo,
>>
> 
> Hi
> 
>> Hope you are doing great!
>>
> 
> Sort of, thanks :)
> 
>> I was wondering if you got a chance to post these patches to LKML for
>> review and inclusion... (No hurry, of course!)
>>
> 
> 
> I'm having troubles testing these new patches on 5.2-rc4.  As it
> happened with the first release candidates for 5.1, the CPU of my test
> machine (Intel Core i7-2760QM@...0GHz) is so slowed down that results
> are heavily distorted with every I/O scheduler.
> 

Oh, that's unfortunate!

> Unfortunately, I'm not competent enough to spot the cause of this
> regression in a feasible amount of time.  I hope it'll go away with
> next release candidates, or I'll test on 5.1.
> 

Sounds good to me!

>> 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?
>>
> 
> I have implanted my fixes on the existing throughput-boosting
> infrastructure of BFQ.  CFQ doesn't have such an infrastructure.
> 
> If you need I/O control with older kernels, you may want to check my
> version of BFQ for legacy block, named bfq-sq and available in this
> repo:
> https://github.com/Algodev-github/bfq-mq/
>

Great! Thank you for sharing this!
 
> I'm willing to provide you with any information or help if needed.
> 
Thank you!

Regards,
Srivatsa
VMware Photon OS