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

[Peter Williams]

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@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.
>
>
> 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@xxxxxxxxxxxxxx

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

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