Re: [RFC 4/7] change kernel accounting to include steal time

[Rik van Riel <riel@redhat.com>]

On 08/26/2010 04:47 PM, Marcelo Tosatti wrote:
> On Thu, Aug 26, 2010 at 05:28:56PM -0300, Glauber Costa wrote:
>> On Thu, Aug 26, 2010 at 02:23:03PM -0300, Marcelo Tosatti wrote:

>>> Skipping accounting of user/system time whenever there's any stolen
>>> time detected probably breaks u/s accounting on non-cpu-hog loads.

Steal time does not completely skip accounting of user/system
time.  Say that it has been 10ms since the last timer tick, we
are currently in user mode, and 4ms have been accounted as steal
time.

The steal time accounting code will then account 4ms as steal
time, and 6ms as user time.

It does not "skip accounting of user/system time" at all.

>> I am willing to test some workloads you can suggest, but right now,
>> (yeah, I mostly used cpu-hogs), this scheme worked better.
>>
>> Linux does statistical sampling for accounting anyway, so I don't see
>> it getting much worse.
>
> A "cpu hog" that sleeps 1us every 1ms.

This kind of program can be an issue with or without
steal time.

I don't see steal time make the situation any worse.

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