Re: 2.6.8-rc1-np1
From: Nick Piggin
Date: Sat Jul 17 2004 - 04:27:09 EST
Felipe Alfaro Solana wrote:
On Sat, 2004-07-17 at 15:23 +1000, Nick Piggin wrote:
Scheduler behaviour is generally pretty good now so I've increased the
timeslice size to see how far I can push it. Some workloads really demand
small timeslices though, so I've added /proc/sys/kernel/base_timeslice.
If you have any problems with the default, please report it to me, and
check if lowering this value helps.
On my 700Mhz Pentium III Mobile laptop, I feel that 256ms is too high
for the system to keep interactive when a CPU hog is running. For
Yeah, it is probably a bit too large here too. A burst of activity
from X can cause xmms to skip slightly. Probably 128 or 64 would
be a decent default.
example, running "while true; do a=2; done" makes the system pretty
sluggish with the default timeslice. This is noticeable while dragging
windows around (the movement is jerky and doesn't feel smooth).
Decreasing the timeslie to 50ms, or even better, 25ms, makes the system
behave much much better, although it will decrease throughput
considerably, I guess.
It usually isn't too bad for desktops, but is more important on
systems with more CPUs and bigger caches.
On this dual P3 with 256K L2 cache, a make -j8 vmlinux uses
162.16user 15.43system, ~150ctxsw/s with base_timeslice = 10000
163.88user 16.16system, ~300ctxsw/s with base_timeslice = 32
192.65user 17.27system, ~1300ctxsw/s with base_timeslice = 1
So you come to the point of diminishing returns very quickly, and
32 or even 16 or 8 are probably fine values for a desktop system
and worth the small cost for CPU intensive tasks.
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