linux-kernel - Re: [RFC PATCH 0/4] cgroup aware workqueues

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Date:	Mon, 04 Apr 2016 13:00:12 -0400
From:	Bandan Das <bsd@...hat.com>
To:	"Michael Rapoport" <RAPOPORT@...ibm.com>
Cc:	jiangshanlai@...il.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, mst@...hat.com,
	Tejun Heo <tj@...nel.org>
Subject: Re: [RFC PATCH 0/4] cgroup aware workqueues

...
>> There have been discussions about this in the past and iirc, most people 
> agree
>> about not going the byos* route. But I am still all for such a proposal 
> and if
>> it's good/clean enough, I think we can definitely tear down what we have 
> and
>> throw it away! The I/O scheduling part is intrusive enough that even the 
> current
>> code base has to be changed quite a bit.
>
> The "byos" route seems more promising with respect to possible performance 
> gains, but it will definitely add complexity, and I cannot say if the 
> added complexity will be worth performance improvements.
>
> Meanwhile, I'd suggest we better understand what causes regression with 
> your current patches and maybe then we'll be smarter to get to the right 
> direction. :)
>

Agreed, let's try to understand the cause of the "underperformance" with wqs.
I disabled WQ_CGROUPS that effectively disables my changes and I can still
consistently reproduce the lower numbers.

>> *byos = bring your own scheduling ;)
>> 
>> > Thanks.
>
> --
> Sincerely yours,
> Mike.
>
> [1] https://lwn.net/Articles/650857/