Subject: Re: [linux-audio-dev] info point on linux hdr
From: Jussi Laako (jussi_AT_jlaako.pp.fi)
Date: Sat Apr 22 2000 - 16:04:54 EEST
Benno Senoner wrote:
>
> Jussi used way to small testsizes therefore the results were not
> reliable.
Depends on machine... ;-)
I wrote the test in my s-l-o-w server (P100) with not-so-new IDE disks.
Writing 300 MB file with that machine would take LONG time, that's why I
deffed the size.
> you save the time it takes to copy 300MB from RAM to RAM, which is
> 0.5 - 1secs , that means at most % of performance increase.
That of course depends also on CPU/bus speed. Anyway, mem copy of 300 MB
doesn't take much time.
One big problem with Linux (and many other OS's) is lack of IO priorization.
Any single user can easily "hang" the machine by generating large amount of
disk IO and thus messing up any audio realtime processing.
Good example of that was few days ago, when Acrobat Reader got wild on my
laptop by starting to allocate and commit huge amounts of memory. Whole
machine gone to unusable because kernel was swapping like nuts. Only way to
get out of this infinite loop was to take battery out the machine...
I believe we need kernel feature to limit bus bandwidth single user or
process can use. Kernel should limit time spent on swapping by putting
memory hog process to hold. Same thing with IO hogs by dropping those
processes down on scheduling list. This is also DOS type security bug.
It would be nice to be able to give sound card driver higher priority
compared to disk driver.
- Jussi Laako
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