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SubjectRe: Scheduler fairness problem on 2.6 series (Attn: Nick Piggin and others)
Date
Peter Williams writes:

> Peter Williams wrote:
>> Peter Williams wrote:
>>
>>> William Lee Irwin III wrote:
>>>
>>>> On Tue, Aug 10, 2004 at 07:21:43PM -0700, spaminos-ker@yahoo.com wrote:
>>>>
>>>>> I am not very familiar with all the parameters, so I just kept the
>>>>> defaults
>>>>> Anything else I could try?
>>>>> Nicolas
>>>>
>>>>
>>>>
>>>>
>>>> No. It appeared that the SPA bits had sufficient fairness in them to
>>>> pass this test but apparently not quite enough.
>>>>
>>>
>>> The interactive bonus may interfere with fairness (the throughput
>>> bonus should actually help it for tasks with equal nice) so you could
>>> try setting max_ia_bonus to zero (and possibly increasing
>>> max_tpt_bonus). With "eb" mode this should still give good interactive
>>> response but expect interactive response to suffer a little in "pb"
>>> mode however renicing the X server to a negative value should help.
>>
>>
>> I should also have mentioned that fiddling with the promotion interval
>> may help.
>
> Having reread your original e-mail I think that this problem is probably
> being caused by the interactive bonus mechanism classifying the httpd
> server threads as "interactive" threads and giving them a bonus. But
> for some reason the daemon is not identified as "interactive" meaning
> that it gets given a lower priority. In this situation if there's a
> large number of httpd threads (even with promotion) it could take quite
> a while for the daemon to get a look in. Without promotion total
> starvation is even a possibility.
>
> Peter
> PS For both "eb" and "pb" modes, max_io_bonus should be set to zero on
> servers (where interactive responsiveness isn't an issue).
> PPS For "sc" mode, try setting "interactive" to zero and "compute" to 1.

No, compute should not be set to 1 for a server. It is reserved only for
computational nodes, not regular servers. "Compute" will increase latency
which is undersirable.

Cheers,
Con

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