Re: BUG: sched=credit2 crashes system when using cpupools

From: Dario Faggioli <dfaggioli@suse.com>
To: Steven Haigh <netwiz@crc.id.au>, Jan Beulich <JBeulich@suse.com>
Cc: George Dunlap <George.Dunlap@eu.citrix.com>,
	xen-devel <xen-devel@lists.xenproject.org>,
	Juergen Gross <jgross@suse.com>
Subject: Re: BUG: sched=credit2 crashes system when using cpupools
Date: Wed, 12 Sep 2018 17:11:20 +0200	[thread overview]
Message-ID: <9d3beeffa3ed724f751dc190b3de4d34a22f1ea3.camel@suse.com> (raw)
In-Reply-To: <faf61a4a900b3404de8077357e898159@crc.id.au>

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On Thu, 2018-08-30 at 18:49 +1000, Steven Haigh wrote:
> On 2018-08-30 18:33, Jan Beulich wrote:
> > > > > 
> > Anyway - as Jürgen says, something for the scheduler
> > maintainers to look into.
> 
Ok, I'm back.

> Yep - I just want to confirm that we tested this in BOTH NUMA 
> configurations - and credit2 crashed on both.
> 
> I switched back to sched=credit, and it seems to work as expected:
> # xl cpupool-list
> Name               CPUs   Sched     Active   Domain count
> Pool-node0          12    credit       y          3
> Pool-node1          12    credit       y          0
> 
Wait, in a previous message, you said: "A machine where we could get
this working every time shows". Doesn't that mean creating a separate
pool for node 1 works with both Credit and Credit2, if the node has
memory?

I mean, trying to clarifying, my understanding is that you have to
systems:

system A: node 1 has *no* memory
system B: both node 0 and node 1 have memory

Creating a Credit pool with pcpus from node 1 always work on both
systems.

OTOH, when you try to create a Credit2 pool with pcpus from node 1,
does it always crash on both systems, or does it work on system B and
crashes on system A ?

I do have a NUMA box with RAM in both nodes (so similar to system B).
Last time I checked, what you're trying to do worked there, pretty much
with any scheduler combination, but I'll recheck.

I don't have a box similar to system A. I'll try to remove some of the
RAM from that NUMA box, and check what happens.

Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Software Engineer @ SUSE https://www.suse.com/

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