On Mon, Dec 17, 2001 at 10:09:22PM -0800, Linus Torvalds wrote:
> Well, looking at the issue, the problem is probably not just in the sb
> driver: the soundblaster driver shares the output buffer code with a
> number of other drivers (there's some horrible "dmabuf.c" code in common).
> And yes, the dmabuf code will wake up the writer on every single DMA
> complete interrupt. Considering that you seem to have them at least 400
> times a second (and probably more, unless you've literally had sound going
> since the machine was booted), I think we know why your setup spends time
> in the scheduler.
> A number of sound drivers will use the same logic.
I've chucked the sb32 and plugged in the emu10k1 I had been planning
to install for a while, to good effect. It's not an ISA sb16, but it
apparently uses the same driver.
I'm getting an overall 1% reduction in system load, and the following
"top 5" profile:
53374 total 0.0400
11430 default_idle 238.1250
8820 handle_IRQ_event 91.8750
2186 do_softirq 10.5096
1984 schedule 1.2525
1612 number 1.4816
1473 __generic_copy_to_user 18.4125
Oddly, I'm getting even more interrupts than I saw with the sb32...
0: 2752924 XT-PIC timer
9: 14223905 XT-PIC EMU10K1, eth1
(eth1 generates orders of magnitude fewer interrupts than the timer)
On Mon, Dec 17, 2001 at 10:09:22PM -0800, Linus Torvalds wrote:
> You may be able to change this more easily some other way, by using a
> larger fragment size for example. That's up to the sw that actually feeds
> the sound stream, so it might be your decoder that selects a small
> fragment size.
> Quite frankly I don't know the sound infrastructure well enough to make
> any more intelligent suggestions about other decoders or similar to try,
> at this point I just start blathering.
Already more insight into the problem I was experiencing than I had
before, and I must confess to those such as myself this lead certainly
seems "plucked out of the air". Good work! =)
On Mon, Dec 17, 2001 at 10:09:22PM -0800, Linus Torvalds wrote:
> But yes, I bet you'll also see much less impact of this if you were to
> switch to more modern hardware.
I hear from elsewhere the emu10k1 has a bad reputation as source of
excessive interrupts. Looks like I bought the wrong sound card(s).
Maybe I should go shopping. =)
Thanks a bunch!
Bill
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