Re: [PATCH] improving O(1)-J9 in heavily threaded situations

[Jussi Laako <jussi.laako@kolumbus.fi>]

Ingo Molnar wrote:
> 
> there is one more thing in the -K2 patch that could cause your problems.
> In kernel/softirq.c, you'll find this line:
> //__initcall(spawn_ksoftirqd);
> please uncomment it - this was just a debugging thing that was left in 
> the patch accidentally. I've made a -K3 patch that has this fixed. Do you
> still see the audio problems?

I did this and also tried -K3. It didn't fix the problem.

I addded lost block count printing to the SCHED_FIFO server processes. Most
of the loss (about 75%) happens at lowest level soundcard server and rest in
distributor process. Usually it looses 1 block at time but occasionally
there is peak of about 18 lost blocks.

If I make the client process read larger blocks (> 4kB) from the distributor
process number of lost blocks at soundcard server raises significantly. I
can make it a bit smaller without increased loss, but of course it means
larger overhead and eventually more lost blocks if made something like 512
bytes. 4 kB is optimal block size as it's also internal block size used by
soundcard and distributor servers.

4 kB block size means 2.9 ms in time in this case.


 - Jussi Laako

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