On 22.03.2012 08:53, Gleb Natapov wrote:
On Wed, Mar 21, 2012 at 06:31:02PM +0100, Peter Lieven wrote:
On 21.03.2012 12:10, David Cure wrote:
hello,
Le Tue, Mar 20, 2012 at 02:38:22PM +0200, Gleb Natapov ecrivait :
Try to add<feature policy='disable' name='hypervisor'/> to cpu
definition in XML and check command line.
ok I try this but I can't use<cpu model> to map the host cpu
(my libvirt is 0.9.8) so I use :
<cpu match='exact'>
<model>Opteron_G3</model>
<feature policy='disable' name='hypervisor'/>
</cpu>
(the physical server use Opteron CPU).
The log is here :
http://www.roullier.net/Report/report-3.2-vhost-net-1vcpu-cpu.txt.gz
And now with only 1 vcpu, the response time is 8.5s, great
improvment. We keep this configuration for production : we check the
response time when some other users are connected.
please keep in mind, that setting -hypervisor, disabling hpet and
only one vcpu
makes windows use tsc as clocksource. you have to make sure, that your vm
is not switching between physical sockets on your system and that you have
constant_tsc feature to have a stable tsc between the cores in the
same socket. its also likely that the vm will crash when live migrated.
All true. I asked to try -hypervisor only to verify where we loose
performance. Since you get good result with it frequent access to PM
timer is probably the reason. I do not recommend using -hypervisor for
production!
@gleb: do you know whats the state of in-kernel hyper-v timers?
Vadim is working on it. I'll let him answer.
@avi, gleb: another option would be to revisit the old in-kernel
pm-timer implementation
and check if its feasible to use this as an alternative. it would also
help non hyper-v aware
systems (i think bsd and old windows like xp). i rebased this old
implementation and can
confirm that it does also solve the performance slow down.
peter
peter
David.
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Gleb.
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