Re: Multiple Mantis devices gives me glitches

[Vidar Tyldum <vidar@tyldum.com>]

13.12.2011 08:31, Marko Ristola:
> 
> Hi
> 
> Here is a patch that went into Linus GIT this year.
> It reduces the number of DMA transfer interrupts into one third.
> Linus released 2.6.38.8 doesn't seem to have this patch yet

Good news, combining this patch with IRQ management fixes the problem for me.

Status:
 * Stock 2.6.38.8 mantis, no IRQ management:     glitches
 * Stock 2.6.38.8 mantis, with IRQ management:   glitches
 * Patched 2.6.38.8 mantis, no IRQ management:   glitches (less)
 * Patched 2.6.38.8 mantis, with IRQ management: very few glitches
 * Same as above, but latency_timer set to 0xff: no glitches in one hour

The patch was applied to 2.6.38.8 (in Ubuntu terms: 2.6.38-13-generic-pae).
Tests involved having VDR record on three different transponders at the same
time, which means lots of IO and all three cards active at once.

For IRQ management I tried both 'irqbalancer' and manual setting with IRQ
affinity (which is basicly what irqbalancer does).

I tried playing with the latency timer on the other scenarios, not only the
last one, but all had glitches anyways.

Not sure what to conclude with:
 - Unfortunate IRQ handling on this CPU (two and two share IRQ handling)?
 - Too many interrupts generated by driver (design issues)?
 - Driver not handling SMP gracefully?
...or a combination?

Your patch is definately needed. Is there anything I can do to help getting
it in?


-- 
Vidar Tyldum
                              vidar@tyldum.com               PGP: 0x3110AA98