Messages in this thread | | | Date | Wed, 11 Aug 2004 13:44:10 +1000 | From | Peter Williams <> | Subject | Re: Scheduler fairness problem on 2.6 series (Attn: Nick Piggin and others) |
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Peter Williams wrote: > 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.
I've just run your tests on my desktop and with max_ia_bonus at its default value I see the "delta = 3" with 20 threads BUT when I set max_ia_bonus to zero they stop (in both "eb" and "pb" mode). So I then reran the tests with 60 threads and zero max_ia_bonus and no output was generated by your testdelay script in either "eb" or "pb" modes. I didn't try "sc" mode as I have a ZAPHOD kernel loaded (not HYDRA) but Con has reported that the problem is absent in his latest patches so I'll update the "sc" mode in HYDRA to those patches.
Peter -- Peter Williams pwil3058@bigpond.net.au
"Learning, n. The kind of ignorance distinguishing the studious." -- Ambrose Bierce
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