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Re: Lower-latency kernels?



On Tue, 2002-06-04 at 00:16, Christian Jaeger wrote: 
> 
> 2.)  I am now running 2.4.18 with 
> http://penguinppc.org/~eb/files/2.4.18-elf-fix.patch and 
> 2.4.18-rc1-low-latency.patch from Andrew Morton's Website 
> (zipworld.com.au something) (and also the attached one). It runs, 
> also mol is no problem; however: I've compiled it with the sysctl in 
> /proc, and tried switching with
>    echo 1 > /proc/sys/kernel/lowlatency
> or echo 0 > ...
> but haven't noticed any difference whatsoever yet. I've mainly tried 
> untarring kernel tarballs and copying around with or without nice and 
> at the same time dragged a window around in X. The window is sluggish 
> either way during phases where it seems the CPU is working and not 
> the disk. Now I would have expected that since X runs with elevated 
> priority (-10) it should profit from lower latency.

Beware that the window manager (and possibly other clients when their windows
get exposed) is also involved when moving windows.

> I guess lowlat only helps for realtime priority processes?

Maybe, or I guess it rather decreases worst-case latencies but doesn't
necessarily help in the average case.

> Maybe the O(1) schedular would help more in that case?

I doubt it, I understand it mostly makes a difference with lots of processes
running on multiple CPUs. But why not try? :)


-- 
Earthling Michel Dänzer (MrCooper)/ Debian GNU/Linux (powerpc) developer
XFree86 and DRI project member   /  CS student, Free Software enthusiast


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