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

[Ivan Voras]

2009/10/13 Larry Rosenman <ler at lerctr.org>:

>>>> 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?

Hi,

It is ESXi 3.5 - but if the problem is really in ESXi I presume anyone
could reproduce it. My setup is nothing special - Xeon 5405, 8 GB RAM,
SATA drives on ICH9.

As for what data is needed, it depends on what you can get - from this
discussion thread it looks like it would be enough to verify that disk
IO doesn't leave VM processes waiting (i.e. that disk IO doesn't
interfere with CPU-bound or idle virtual machines). Though now when I
think of it - doesn't Linux ATA driver poll IO in some funky way,
expecting to get lower latency that way?