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SubjectRe: another must-fix: major PS/2 mouse problem
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On Mon, 2003-07-28 at 23:14, Andrew Morton wrote:
> Albert Cahalan <albert@users.sourceforge.net> wrote:

> > OK, I did this. Now, in microseconds, I get:
> >
> > ------------------------
> > IRQ use min max
> > --- -------- --- -------
> > 0 timer 40 103968
> > 1 i8042 14 1138 (was 389773)
> > 2 cascade - -
> > 3 - - -
> > 4 serial 29 56
> > 5 uhci-hcd - -
> > 6 - 690 690
> > 7 - 40 40
> > 8 - - -
> > 9 - - -
> > 10 - - -
> > 11 eth0 73 31332 (was 1535331)
> > 12 i8042 18 215 (was 102895)
> > 13 - - -
> > 14 ide0 7 43846
> > 15 ide1 7 12
> > ------------------------
> >
> > boomerang_interrupt itself takes 4 to 59 microseconds.
>
> So this looks OK, yes?

I suppose boomerang_interrupt itself is OK.
Spending 104 ms in IRQ 0, 31 ms in IRQ 11, and
44 ms in IRQ 14 is not at all OK. I was hoping
to get under 200 microseconds for everything.

> (Is that instrumentation patch productisable?
> Looks handly, albeit a subset of microstate accounting)

Not really. I printk() when a value exceeds the
saved maximum, then scan my logs for the first
and last values. There's also hard-coded knowledge
of my 1-GHz CPU, which lets me convert to microseconds
as follows: us = (unsigned)(ns64>>3)/125u;

(that lets me handle up to 32 seconds)

Huh. So the minimum value is really the first value.
Later values could be less, but that's not important.
I suppose that true min/max via a /proc file would
be pretty easy to implement. I like my 1-GHz hack.
I like a TSC that measures in nanoseconds too.

> > Then I switched to 2.6.0-test2. Testing more, I get the
> > problem with or without SMP and with or without
> > preemption. Here's a chunk of my log file:
> >
> > Loosing too many ticks!
> > TSC cannot be used as a timesource. (Are you running with SpeedStep?)
> > Falling back to a sane timesource.
> > psmouse.c: Lost synchronization, throwing 3 bytes away.
> > psmouse.c: Lost synchronization, throwing 1 bytes away.
> >
> > Arrrrgh! The TSC is my only good time source!
>
> Arrrgh! More PS/2 problems!
>
> I think the lost synchronisation is the problem, would you agree?

It's one problem. It's a problem other people have seen.
My TSC should be good though; I'd like to use it.
At times ntpd (the NTP daemon) gets really unhappy with
the situation, yanking my clock ahead by up to 10 minutes
to compensate for lost time.

> The person who fixes this gets a Nobel prize.
>
> > Remember that this is a pretty normal system. I have
> > a Red Hat 8 install w/ required upgrades, ext3, IDE,
> > a 1-GHz Pentium III, a boring VIA chipset, etc.
> >
> > To reproduce, I do some PS/2 mouse movement while
> > doing one of:
> >
> > a. Lots of concurrent write() and sync() activity to ext3.
> > b. Lots of NFSv3 traffic.
>
> ie: lots of interrupt traffic causes the PS2 driver to go whacky?

I guess so. The ext3+IDE behavior seems to lift the blame
from boomerang_interrupt. Using ext3+IDE, I seem to need
a couple minutes to reproduce the problem. NFSv3+Ethernet
will give me the problem almost instantly.



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