Re: Laptop exhibits erratic responsiveness

On Sun, Nov 29, 2020 at 03:20:15PM +0100, Mateusz Guzik wrote:
> On 11/29/20, David Wolfskill <david_at_catwhisker.org> wrote:
> > On Sat, Nov 28, 2020 at 10:47:57AM -0500, Jonathan Looney wrote:
> >> FWIW, I would try running lockstat on the box. (My supposition is that
> >> the
> >> delay is due to a lock. That could be incorrect.  Lockstat may provide
> >> some
> >> clue as to whether this is a line of inquiry worth pursuing.)
> >> ....
> >
> > Thanks (again), Jonathan.
> >
> > So... I did that (during this morning's daily upgrade cycle); the
> > results may be "of interest" to some.
> ...
> > http://www.catwhisker.org/~david/FreeBSD/head/lockstat/README
> ...
> 
> According to the data you got the entire kernel "freezes" every 11-12
> seconds. So something way off is going on there.
> 
> Given that the bug seems to be reproducible I think it would be best
> if you just bisected to the offending commit.
> 
> -- 
> Mateusz Guzik <mjguzik gmail.com>

I had thought that the issue arose  (as noted in my initial message)
around 09 Nov, which was the day that my daily update on head went from
r367484 to r367517.

So for my inital attempt at a "before the breakage" kernel (& world), I
"updated" sources to r367444, as I had updated to that revision on 07
Nov.

Testing (again, via "ping albert") still showed most RTTs around 0.600
ms, but (around) every 11th packet, I would see an RTT in the 400 - 650
ms range -- around a factor of 1000(ish).  So while I was not seeing
RTTs in excess of 68 seconds (as I did at least one time for the initial
message), I believe(d) that the underlying issue still existed at
r367444.

Lather, rinse, repeat -- for:

* r367484 (from 08 Nov)
* r367243 (from 01 Nov)
* r366312 (from 01 Oct)
* r363759 (from 01 Aug)

At this point, I was questioning many assumptions, so I cleared /usr/obj
completely and then updated back to r368143... and the issue remained.

(The laptop was quite busy yesterday.)

I definitely do NOT see anything like this running stable/12 (presently
at r368181).

I will try some experiments with another laptop (a newer one, for which
the built-in mouse is detected weirdly, making it annoying to use for me
-- but I can still ping from it).

Peace,
david
-- 
David H. Wolfskill                              david_at_catwhisker.org
"Make America Great Again," he said -- and THIS is what he did??!?

See http://www.catwhisker.org/~david/publickey.gpg for my public key.