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

From: Peter Williams
Date: Tue Aug 10 2004 - 22:24:16 EST


Peter Williams wrote:
Peter Williams wrote:

William Lee Irwin III wrote:

On Tue, Aug 10, 2004 at 07:21:43PM -0700, spaminos-ker@xxxxxxxxx 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.
--
Peter Williams pwil3058@xxxxxxxxxxxxxx

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

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