linux-kernel - Re: [RFC/PATCH 0/4] CPUSET driven CPU isolation

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Date:	Thu, 28 Feb 2008 09:48:11 -0800
From:	Max Krasnyanskiy <maxk@...lcomm.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Oleg Nesterov <oleg@...sign.ru>,
	Steven Rostedt <rostedt@...dmis.org>,
	Paul Jackson <pj@....com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC/PATCH 0/4] CPUSET driven CPU isolation

Ingo Molnar wrote:
> * Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
> 
>> My vision on the direction we should take wrt cpu isolation.
>>
>> Next on the list would be figuring out a nice solution to the 
>> workqueue flush issue.
> 
> nice work Peter, i find this "system sets" extension to cpusets a much 
> more elegant (and much more future-proof) solution than the proposed 
> spreadout of the limited hack of isolcpus/cpu_isolated_map. It 
> concentrates us on a single API and on a single mechanism to handle 
> isolation matters. (be that for clustering/supercomputing or real-time 
> purposes)
Come on Ingo. You make it sounds like it's radically different solution.
At the end of the day we have a bitmap that represents which CPUs can be used 
for the kernel stuff. How is that different ?
I was saying all along that cpusets is a higher level API and was discussing 
or trying to discuss (people were ignoring my questions) ways to integrate it.

> Thanks for insisting on using cpusets for this!
> 
> i've queued up your patches in sched-devel.git, and lets make sure this 
> has no side-effects on existing functionality. (it shouldnt)
Hmm, that was easy. Not a single ack. Even the core part is not complete yet. 
I pointed out several issues. Like the fact that it does not provide full 
isolation because it does not move timers, does not handle workqueues.
I did not even get a chance to test this stuff properly and see if it actually 
solves the usecase I was solving with my patches.
_Obviously_ we could not have taken my tested solution and evolved it in the 
direction people wanted to see it evolve, ie integration with the cpusets :(.

My main concern is that it introduces a whole new set of notifiers that 
perform similar functions to what CPU hotplut already does.

Max
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