Messages in this thread | | | Subject | Re: Which kernel is the best for a small linux system? | From | Mike Galbraith <> | Date | Thu, 16 Mar 2006 16:24:19 +0100 |
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On Tue, 2006-03-14 at 10:05 +0100, Mike Galbraith wrote: > On Tue, 2006-03-14 at 08:29 +0100, Ingo Molnar wrote: > > * Willy Tarreau <willy@w.ods.org> wrote: > > > > > scheduler is still a big problem. Not only we occasionally see people > > > complaining about unfair CPU distribution across processes (may be > > > fixed now), but the scheduler still gives a huge boost to I/O > > > intensive tasks which do lots of select() with small time-outs, which > > > makes it practically unusable in network-intensive environments. I've > > > observed systems on which it was nearly impossible to log in via SSH > > > because of this, and I could reproduce the problem locally to create a > > > local DoS where a single user could prevent anybody from logging in. > > > 2.6.15 has improved a lot on this (pauses have reduced from 35 seconds > > > to 4 seconds) but it's still not very good. > > Hi Willy, > > BTW, if you try my stuff, it'd be good to try just the "cleanup" patch > first. It seems very likely to me that your problem is mostly caused by > the sleep_avg multiplier. If the first patch cures your woes, try > killing just the multiplier in virgin source.
Hi again Willy,
Well. I've done some testing with apache, and I can reproduce the problem... too darn well in fact. It's really bad in 2.6.15 here as well, and while removing the sleep_avg multiplier and the requeue in schedule() improved things quite a bit, I still have nasty 30s delays while trying to pipe commands. These things alone apparently aren't going to be enough if you want to ssh into a busy server.
-Mike
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