Messages in this thread | | | Date | Tue, 04 Jul 2000 14:00:56 +1000 | From | Andrew Morton <> | Subject | Re: [linux-audio-dev] Re: [DATAPOINT] kernels and latencies |
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Roger Larsson wrote: > > > I don't think mmap002 is a very pointful test. "Don't > > run mmap002 when you're doing multimedia". > > > > Sadly it is... > There will be other programs that utilizes mmap that can give the same > problems...
True, but sys_mmap() is not appearing on the radar screen.
The point the audio guys have been making is that they require reasonable latency on a *dedicated machine*. That changes the game a lot.
I'll take a peek at sys_msync(), but I think "don't do that" is a solution here.
> > ... > > 160 milliseconds in sys_msync() -> "don't use sys_msync()...." > > What do you use to get this output?
It's based on http://www.uow.edu.au/~andrewm/linux/#timepegs
I've added a lot of new stuff for this activity. I'll get a new set of patches and docco out later this week.
I think the sys_clone() and sys_exit() numbers may be wrong - the current instrumentation is probably getting confused by system calls which are entered once and exitted twice or never..
Pretty soon, I'll ask the audio people to put their money where their mouthes are, and start testing, analysing and helping to "file off the high spots".
> > Note: I have seen X causing 50 ms latencies... > [aux_write_dev+26/28]
awwwww.. Yuk. What a piggy little function!
That's going to cause network overruns at 100mbits, heaven knows what else. It needs a redesign.
In the meanwhile, this probably means that people who require low latency will need to buy an RS232 mouse. That's OK.
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