Re: PHP performance on Xen domU with mulitple vcpu

[mlelstv%serpens.de@localhost (Michael van Elst)]

gdt%lexort.com@localhost (Greg Troxel) writes:

>> count  value
>> 239726 1743694322.907498
>> 119400 1743694324.187487
>> 327599 1743694325.467476
>> 174425 1743694326.747465
>> 138850 1743694328.027453

>Wow, that is messed up!


That looks like a common behaviour of virtual machines, when they
cannot keep up with interrupt load.

You get 100-300k times the same timecounter value (within the 10ms
interval to the next tick). Then the interrupt is processed, but
the VM tries to catch up with real time and quickly handles a batch
of previously "missed" timer interrupts.

Ignore the last 4 "digits" of the timecounter value and you see:

1743694322.90
+ 1.28
1743694324.18
+ 1.28
1743694325.46
+ 1.28
1743694326.74
+ 1.28
1743694328.02

So each step of the timecounter catches up with exactly 128 interrupts
that were delivered as a batch.