Messages in this thread | | | Date | Wed, 13 Aug 2003 13:24:40 +1000 | From | Nick Piggin <> | Subject | Re: [PATCH] O13int for interactivity |
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Gene Heskett wrote:
>On Tuesday 12 August 2003 22:08, jw schultz wrote: > >>On Tue, Aug 12, 2003 at 09:58:04PM +1000, Nick Piggin wrote: >> >>>I have been hearing of people complaining the scheduler is worse >>>than 2.4 so its not entirely obvious to me. But yeah lots of it is >>>trial and error, so I'm not saying Con is wasting his time. >>> >>I've been watching Con and Ingo's efforts with the process >>scheduler and i haven't seen people complaining that the >>process scheduler is worse. They have complained that >>interactive processes seem to have more latency. Con has >>rightly questioned whether that might be because the process >>scheduler has less control over CPU time allocation than in >>2.4. Remember that the process scheduler only manages the >>CPU time not spent in I/O and other overhead. >> >>If there is something in BIO chewing cycles it will wreak >>havoc with latency no matter what you do about process >>scheduling. The work on BIO to improve bandwidth and reduce >>latency was Herculean but the growing performance gap >>between CPU and I/O is a formidable challenge. >> > >In thinking about this from the aspect of what I do here, this makes >quite a bit of sense. In running 2.6.0-test3, with anticipatory >scheduler, it appears the i/o intensive tasks are being pushed back >in favor of interactivity, perhaps a bit too aggressively. An amanda >estimate phase, which turns tar loose on the drives, had to be >advanced to a -10 niceness for the whole tree of processes amanda >spawns before it began to impact the setiathome use as shown by the >nice display in gkrellm. Normally there is a period for maybe 20 >minutes before the tape drive fires up where the machine is virtually >unusable due to gzip hogging things, like the cpu, during which time >seti could just as easily be swapped out. It remained at around 60%! > >It did not hog/lag near as badly as usual, and the amanda run was over >an hour longer than it would have been in 2.4.22-rc2. > >It is my opinion that all this should have been at setiathomes >expense, which is also rather cpu intensive, but it didn't seem to be >without lots of forceing. This is what the original concept of >niceness was all about. Or at least that was my impression. From >what it feels like here, it seems the i/o stuff is whats being >choked, and choked pretty badly when using the anticipatory >scheduler. > >I've read rumors that a boottime option can switch it to somethng >else, so what do I do to switch it from the anticipatory scheduler to >whatever the alternate is?, so that I can get a feel for the other >methods and results. >
Boot with "elevator=deadline" to use the more conventional elevator.
It would be good if you could get some numbers 2.4 vs 2.6, with and without seti running. Sounds like a long cycle though so you probably can't be bothered!
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