Messages in this thread | | | Date | Sun, 17 Nov 2002 23:08:06 -0800 | From | Andrew Morton <> | Subject | Re: 2.5.47 scheduler problems? |
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Tim Connors wrote: > > > I used to be able to wave a window poorly at make -j25 (swapping heftily), > > fairly smoothly at make -j20, and smoothly at make -j15 or below. This > > with no SCHED_RR/SCHED_FIFO. (I haven't done much testing like this in > > quite a while though) > > Perhaps you should consider buying an extra 29 CPU's for you desktop? >
No. He's saying that it used to be OK, but it has got worse.
A much simpler test is to start a big compilation and then madly waggle an X window around. Goes OK for a few seconds, and then seizes up quite horridly. Presumably because the scheduler has suddenly decided that the X server has become a "batch" process and is scheduling it in a similar manner to the compilation.
If you stop wiggling the window for 5-10 seconds it comes back. Presumably because the scheduler has decided that the X server is "interactive" again.
When it happens, it's *very* bad. The mouse cursor doesn't move for 0.5-1.0 seconds and then takes great leaps. It is unusable.
Strangely it does not happen (much) when the background load is a few busywaits. It has to be a compilation - maybe short-lived batch processes is what triggers it.
For me, the X server is sometimes the victim, and the MUA (netscape4) is frequently victimised. This is because the MUA alternates between periods of interactivity and periods of compute-intensive work (parsing large mailboxes). When this problem strikes you have to just sit there with your arms folded waiting for it to stop.
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