Re: preempt-timing-2.6.8-rc1

[Lenar Lõhmus]

William Lee Irwin III wrote:

> On Tue, Jul 13, 2004 at 06:32:16PM +0300, Lenar L?hmus wrote:
>  
>
> > Machine in question is XP2500+@xxxxxxx (it was overlocked@xxxxxxx during 
> > last test, now running at
> > official speed). Is this really slow for 1ms?
> >    
>
> It should actually be fast enough. I suspect something else, maybe some
> slow devices. What's /proc/interrupts look like?
>  
          CPU0
 0:   60521505    IO-APIC-edge  timer
 1:      11445    IO-APIC-edge  i8042
 8:      33269    IO-APIC-edge  rtc
 9:          0   IO-APIC-level  acpi
14:     523202    IO-APIC-edge  ide0
15:      61761    IO-APIC-edge  ide1
16:   10376547   IO-APIC-level  eth0
19:     522859   IO-APIC-level  ide2
20:     131904   IO-APIC-level  NVidia nForce2, ehci_hcd
21:      66209   IO-APIC-level  ohci_hcd
22:    9165291   IO-APIC-level  ohci_hcd, eth1
NMI:          0
LOC:   60351703
ERR:          0
MIS:          2

> <>exit_notify() isn't a huge surprise unless you're not doing things with
> lots of processes. Actually, it probably is a surprise, since it should
> only hurt when you're doing forkbombs and/or threadbombs.

It probably happened when users where simultaneously logging in (many 
kdeinit processes created at that time).

> Not surprised either. There's probably enough time spent with interrupts
> off the local_irq_save() hurt, and it didn't make your schedule() things
> go away, so my wild guesswork thus far is it made things worse with no
> tangible benefit, so best to drop that local_irq_save() change.
>  
Yeah, ok.

In the meantime couple of these found their way to logs during the night:
3ms non-preemptible critical section violated 2 ms preempt threshold 
starting at search_by_key+0xe3/0xf70 and ending at do_IRQ+0xec/0x130

And this still seems to be very long and real:
50ms non-preemptible critical section violated 2 ms preempt threshold 
starting at snd_pcm_action_lock_irq+0x1b/0x1d0 [snd_pcm] and ending at 
snd_pcm_action_lock_irq+0x65/0x1d0 [snd_pcm]
Trace has this:
[<f9239b09>] snd_pcm_playback_ioctl1+0x49/0x2f0 [snd_pcm]
So maybe this too is ioctl related (non-educated guess)?

Lenar
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