Extreme console latency during disk IO (8.0-RC1, previous releases also affected according to others)

[Larry Rosenman]

On Tue, 13 Oct 2009, Ivan Voras wrote:

> Robert N. M. Watson wrote:
>> 
>> On 13 Oct 2009, at 14:33, Ivan Voras wrote:
>> 
>>>> If (1) is highly variable during I/O, it's almost certainly a property of
>>>> the VM technology you're using, and there's nought to be done about it in
>>>> the guest OS.
>>> 
>>> Here's an example of a ping session with 0.1s resolution during a few
>>> seconds-stall in ssh:
>>> 
>>> 64 bytes from 161.53.72.188: icmp_seq=1576 ttl=64 time=0.383 ms
>>> 64 bytes from 161.53.72.188: icmp_seq=1577 ttl=64 time=0.405 ms
>>> 64 bytes from 161.53.72.188: icmp_seq=1578 ttl=64 time=0.360 ms
>>> 
>>> 64 bytes from 161.53.72.188: icmp_seq=2304 ttl=64 time=4.194 ms
>>> 64 bytes from 161.53.72.188: icmp_seq=2305 ttl=64 time=0.454 ms
>>> 64 bytes from 161.53.72.188: icmp_seq=2306 ttl=64 time=0.376 ms
>>> 
>>> note huge packet loss. It looks like it's VM fault or something like it.
>> 
>> It sounds like the VM is failing to execute the guest during certain types 
>> of I/O. A bit of scheduler tracing in the host OS probably wouldn't go 
>> amiss to confirm that the VM really is suspending the guest 
>
> It's VMWare ESXi underneath, which is *Officially Not Linux* though some 
> ducks may disagree - anyway, I suspect tracing the host in this way is next 
> to impossible without some kind of diamondium-level contract.
>
What information do you need?  I have a platinum VMWare contract.

What version of ESXi?

LER

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-- 
Larry Rosenman                     http://www.lerctr.org/~ler
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