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Message #56817
[Bug 1578155] Re: 'hw:cpu_thread_policy=prefer' misbehaviour
Reviewed: https://review.openstack.org/342709
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=8361d8d6c315bb3ae71c3ff0147f7d5156bc46f3
Submitter: Jenkins
Branch: master
commit 8361d8d6c315bb3ae71c3ff0147f7d5156bc46f3
Author: Stephen Finucane <stephenfinucane@xxxxxxxxxxx>
Date: Tue Jul 19 14:01:53 2016 -0700
Allow linear packing of cores
Given the following single-socket, four-core, HT-enabled CPU topology:
+---+---+ +---+---+ +---+---+ +---+---+
| x | x | | x | | | x | | | | |
+---+---+ +---+---+ +---+---+ +---+---+
1 4 2 5 3 6 4 7
Attempting to boot an instance with four cores and no explicit
'cpu_thread_policy' should be successful, with cores 5,6,4,7 used.
However, the current implementation of this implicit policy attempts to
fit the same number of instance cores onto each host CPU. For example,
a four core instance would result in either a 2*2 layout (two instance
cores on each of two host CPUs), or a 1*4 layout (one instance core on
each of four host CPUs). This may be correct behavior *where possible*,
but if this is not possible then any and all cores should be used.
Resolve this issue by adding a fallthrough case, whereby if the
standard fitting policy fails, a linear assignment is used to properly
fit the instance cores.
Change-Id: I73f7f771b7514060f1f74066e3dea1da8fe74c21
Closes-Bug: #1578155
mitaka-backport-potential
** Changed in: nova
Status: In Progress => Fix Released
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https://bugs.launchpad.net/bugs/1578155
Title:
'hw:cpu_thread_policy=prefer' misbehaviour
Status in OpenStack Compute (nova):
Fix Released
Bug description:
Description
===========
'hw:cpu_thread_policy=prefer' allocates vCPUs in pairs of sibling
threads properly. An odd number of vCPUs will allocate pairs and a
single one. That single one should not be isolated. So 20 available
threads, shall be able to allocate 4 VMs of 5 vCPUs. When booting up
the third VM, it is giving an error.
Steps to reproduce
==================
1.- Creating a flavor:
nova flavor-create pinning auto 1024 10 5
nova flavor-key pinning set hw:cpu_policy=dedicated
nova flavor-key pinning set hw:cpu_thread_policy=prefer
nova flavor-key pinning set hw:numa_nodes=1
2.- Booting up simple VMs:
nova boot testPin1 --flavor pinning --image cirros --nic net-
id=$NET_ID
In my setup, I have 20 available threads:
NUMANode L#0 (P#0 32GB)
Socket L#0 + L3 L#0 (15MB)
L2 L#0 (256KB) + L1d L#0 (32KB) + L1i L#0 (32KB) + Core L#0
PU L#0 (P#0)
PU L#1 (P#12)
L2 L#1 (256KB) + L1d L#1 (32KB) + L1i L#1 (32KB) + Core L#1
PU L#2 (P#2)
PU L#3 (P#14)
L2 L#2 (256KB) + L1d L#2 (32KB) + L1i L#2 (32KB) + Core L#2
PU L#4 (P#4)
PU L#5 (P#16)
L2 L#3 (256KB) + L1d L#3 (32KB) + L1i L#3 (32KB) + Core L#3
PU L#6 (P#6)
PU L#7 (P#18)
L2 L#4 (256KB) + L1d L#4 (32KB) + L1i L#4 (32KB) + Core L#4
PU L#8 (P#8)
PU L#9 (P#20)
L2 L#5 (256KB) + L1d L#5 (32KB) + L1i L#5 (32KB) + Core L#5
PU L#10 (P#10)
PU L#11 (P#22)
NUMANode L#1 (P#1 32GB) + Socket L#1 + L3 L#1 (15MB)
L2 L#6 (256KB) + L1d L#6 (32KB) + L1i L#6 (32KB) + Core L#6
PU L#12 (P#1)
PU L#13 (P#13)
L2 L#7 (256KB) + L1d L#7 (32KB) + L1i L#7 (32KB) + Core L#7
PU L#14 (P#3)
PU L#15 (P#15)
L2 L#8 (256KB) + L1d L#8 (32KB) + L1i L#8 (32KB) + Core L#8
PU L#16 (P#5)
PU L#17 (P#17)
L2 L#9 (256KB) + L1d L#9 (32KB) + L1i L#9 (32KB) + Core L#9
PU L#18 (P#7)
PU L#19 (P#19)
L2 L#10 (256KB) + L1d L#10 (32KB) + L1i L#10 (32KB) + Core L#10
PU L#20 (P#9)
PU L#21 (P#21)
L2 L#11 (256KB) + L1d L#11 (32KB) + L1i L#11 (32KB) + Core L#11
PU L#22 (P#11)
PU L#23 (P#23)
Using the cpu_thread_policy:prefer, the behaviour is ok for the first
two VMs. So 5 threads are allocated in pairs.
[root@nfvsdn-04 ~(keystone_admin)]# virsh vcpupin 2
VCPU: CPU Affinity
----------------------------------
0: 10
1: 22
2: 16
3: 4
4: 8
[root@nfvsdn-04 ~(keystone_admin)]# virsh vcpupin 3
VCPU: CPU Affinity
----------------------------------
0: 17
1: 5
2: 3
3: 15
4: 11
However, eventhough there are enough threads in order to allocate
another 2 VMs with the same flavor, I get the following error booting
up the third VM:
INFO nova.filters Filtering removed all hosts for the request with
instance ID 'cbb53e29-a7da-4c14-a3ad-4fb3aa04f101'. Filter results:
['RetryFilter: (start: 1, end: 1)', 'AvailabilityZoneFilter: (start:
1, end: 1)', 'RamFilter: (start: 1, end: 1)', 'C[r│omputeFilter:
(start: 1, end: 1)', 'ComputeCapabilitiesFilter: (start: 1, end: 1)',
'ImagePropertiesFilter: (start: 1, end: 1)', 'CoreFilter: (start: 1,
end: 1)', 'NUMATopologyFilter: (start: 1, endo: 0)']
There should be enough space for 4 VMs allocated with cpu_thread_policy=prefer flavor.
Expected result
===============
To have 4 VMs up&running with flavor 'pinning'.
Actual result
=============
3rd VM fails at scheduling.
Environment
==========
All-in-one environment.
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References