Re: Scheduler fairness problem on 2.6 series (Attn: Nick Piggin and others)

[Peter Williams <pwil3058@bigpond.net.au>]

Con Kolivas wrote:
> 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.

Sorry, my misunderstanding.

Peter
-- 
Peter Williams                                   pwil3058@bigpond.net.au

"Learning, n. The kind of ignorance distinguishing the studious."
  -- Ambrose Bierce