From: Christian Borntraeger <borntraeger@de.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Yuyang Du <yuyang.du@intel.com>, Ingo Molnar <mingo@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
vincent.guittot@linaro.org, Morten.Rasmussen@arm.com,
dietmar.eggemann@arm.com, pjt@google.com, bsegall@google.com
Subject: Re: group scheduler regression since 4.3 (bisect 9d89c257d sched/fair: Rewrite runnable load and utilization average tracking)
Date: Mon, 26 Sep 2016 16:12:17 +0200 [thread overview]
Message-ID: <13ad6712-a3e2-f084-e12d-6cc947895e32@de.ibm.com> (raw)
In-Reply-To: <20160926121025.GC5016@twins.programming.kicks-ass.net>
On 09/26/2016 02:10 PM, Peter Zijlstra wrote:
> On Mon, Sep 26, 2016 at 02:01:43PM +0200, Christian Borntraeger wrote:
>> They applied ok on next from 9/13. Things go even worse.
>> With this host configuration:
>>
>> CPU NODE BOOK SOCKET CORE L1d:L1i:L2d:L2i ONLINE CONFIGURED ADDRESS
>> 0 0 0 0 0 0:0:0:0 yes yes 0
>> 1 0 0 0 0 1:1:1:1 yes yes 1
>> 2 0 0 0 1 2:2:2:2 yes yes 2
>> 3 0 0 0 1 3:3:3:3 yes yes 3
>> 4 0 0 1 2 4:4:4:4 yes yes 4
>> 5 0 0 1 2 5:5:5:5 yes yes 5
>> 6 0 0 1 3 6:6:6:6 yes yes 6
>> 7 0 0 1 3 7:7:7:7 yes yes 7
>> 8 0 0 1 4 8:8:8:8 yes yes 8
>> 9 0 0 1 4 9:9:9:9 yes yes 9
>> 10 0 0 1 5 10:10:10:10 yes yes 10
>> 11 0 0 1 5 11:11:11:11 yes yes 11
>> 12 0 0 1 6 12:12:12:12 yes yes 12
>> 13 0 0 1 6 13:13:13:13 yes yes 13
>> 14 0 0 1 7 14:14:14:14 yes yes 14
>> 15 0 0 1 7 15:15:15:15 yes yes 15
>>
>> the guest was running either on 0-3 or on 4-15, but never
>> used the full system. With group scheduling disabled everything was good
>> again. So looks like that this bug has also some dependency on on the
>> host topology.
>
> OK, so CPU affinities that unevenly straddle topology boundaries like
> that are hard (and is generally not recommended), but its not
Ok so I created with cpu hotplug a symmetrical CPU topology:
CPU NODE BOOK SOCKET CORE L1d:L1i:L2d:L2i ONLINE CONFIGURED ADDRESS
0 0 0 0 0 0:0:0:0 yes yes 0
1 0 0 0 0 1:1:1:1 yes yes 1
2 0 0 0 1 2:2:2:2 yes yes 2
3 0 0 0 1 3:3:3:3 yes yes 3
4 0 0 0 2 4:4:4:4 yes yes 4
5 0 0 0 2 5:5:5:5 yes yes 5
6 0 0 0 3 6:6:6:6 yes yes 6
7 0 0 0 3 7:7:7:7 yes yes 7
8 0 0 0 - ::: no yes 8
9 0 0 0 - ::: no yes 9
10 0 0 0 - ::: no yes 10
11 0 0 0 - ::: no yes 11
12 0 0 1 4 8:8:8:8 yes yes 12
13 0 0 1 4 9:9:9:9 yes yes 13
14 0 0 1 5 10:10:10:10 yes yes 14
15 0 0 1 5 11:11:11:11 yes yes 15
16 0 0 1 6 12:12:12:12 yes yes 16
17 0 0 1 6 13:13:13:13 yes yes 17
18 0 0 1 7 14:14:14:14 yes yes 18
19 0 0 1 7 15:15:15:15 yes yes 19
Same effect: Only half of the CPUs are used, but the number of
guest CPUs == number of host cpus. Turns out that this is totally
unrelated to this patch set, so it must be something else.
next prev parent reply other threads:[~2016-09-26 14:12 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-26 10:42 Christian Borntraeger
2016-09-26 10:56 ` Peter Zijlstra
2016-09-26 11:42 ` Christian Borntraeger
2016-09-26 11:53 ` Peter Zijlstra
2016-09-26 12:01 ` Christian Borntraeger
2016-09-26 12:10 ` Peter Zijlstra
2016-09-26 12:49 ` Christian Borntraeger
2016-09-26 14:12 ` Christian Borntraeger [this message]
2016-09-26 12:25 ` Vincent Guittot
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