From: johnhm@vaxc.cc.monash.edu.au Subject: Re: I can malloc more memory than I have. Date: 28 Oct 1992 10:30:25 +1100
In article <1992Oct27.105511.17819@klaava.Helsinki.FI>, torvalds@klaava.Helsinki.FI (Linus Torvalds) writes:
> In article <1992Oct27.124302.90427@vaxc.cc.monash.edu.au> johnhm@vaxc.cc.monash.edu.au writes:
>>
>> I think the problem is more general than just running out of virtual memory.
>>It seems as though code that runs in the kernal can realy hog the the machine
>>to the exclusion of all else.
>> For instance, when running X11perf without a coprocessor the machine will seem
>>to grind (almost) to a halt during some of the tests (probably ones using
>>circular functions heavily). Lack of memory doesn't seem to be the problem
>>here as there is no swapping going on (which top confirms whenever it gets a
>>chance to run). It seems a bit strange if the kernal is blocking other processes
>>even if it's just doing floating point emulation. I wonder if this extends to
>>everything the kernal does?
>
> While it's true that a kernel process won't be rescheduled while it
> still runs, this should be no problem: all the system calls, traps and
> interrupt handlers are designed to cope with that (although there may
> actually be some busy waiting in the SCSI-driver). The reason x11perf
> seems to bring the machine to it's knees is not that the kernel hogs all
> the time, but because X11 itself is busy calculating things - while the
> X server does it's calculations, it won't do other screen updating...
>
...
> Linus
So much for my attempt at generalising, sorry Linus.
Still it seems like a bit of a misfeature in X11, it would be nice if X11
could be more adaptive in how it spends its time. Lets hope that someone
from the MIT X11 group is getting frustrated trying to use X11 on a notebook
PC :-).
--John H. Morris E-mail: John.Morris@cc.monash.edu.au Monash University Computer Centre Phone: +61 3 5654763 Wellington Road, FAX: +61 3 5654746 Clayton 3168, Australia.