Re: Laptop exhibits erratic responsiveness

On Mon, Nov 30, 2020 at 05:21:28AM -0800, David Wolfskill wrote:
> ...
> FWIW, the copy of the laptop's "head" kernel config in
> http://www.catwhisker.org/~david/FreeBSD/head/CANARY is current.
> 
> And the only difference between the stable/12 config and the head config
> is:
> 
> g1-48(12.2-S)[3] diff -u FreeBSD-1{2,3}/CANARY
> --- FreeBSD-12/CANARY   2019-07-08 10:43:51.940026000 -0700
> +++ FreeBSD-13/CANARY   2015-03-22 10:03:41.000000000 -0700
> _at__at_ -342,7 +342,7 _at__at_
>  # from some parts of the kernel.  As this makes everything more noisy,
>  # it is disabled by default.
>  #
> -# options      DIAGNOSTIC
> +options        DIAGNOSTIC
>  
>  #
>  # REGRESSION causes optional kernel interfaces necessary only for regression
> 
> Hmmm... so I suppose that re-disbling DIAGNOSTIC might be a reasonable
> thing to try, as well, yeah...?  :-}
> ....

Well, success(ish):

* I was able to reproduce the observed effect using the newer laptop,
running a kernel from 14 Nov (thus, r367674):

* I was able to reproduce the observed effect using the newer laptop,
  running a kernel from 14 Nov (thus, r367674).  (I had cloned the old
  laptop's disk drive and slapped it inito the newer laptop.)

* I then updated the kernel config file ("CANARY") to comment out the
  DIAGNOSTIC option, then rebuilt/installed the kernel.

* Upon reboot, "ping albert" showed remarkably consistent RTTs (compared
  to before) -- e.g., the initial example I posted showed:

  --- albert.catwhisker.org ping statistics ---
  67 packets transmitted, 67 packets received, 0.0% packet loss
  round-trip min/avg/max/stddev =3D 0.428/1024.248/68482.244/8303.513 ms

  On the newer laptop after the above change, I saw:

  --- albert.catwhisker.org ping statistics ---
  30 packets transmitted, 30 packets received, 0.0% packet loss
  round-trip min/avg/max/stddev = 0.463/0.574/0.671/0.054 ms

Please especially note the maxima & standard deviations.


FWIW, I do have (in /boot/loader.conf):

# Try to reduce WITNESS overhead
vm.debug.divisor=4

(which I also utilize at work).

I suppose I will be commenting out that DIAGNOSTIC option now.... :-}

Peace,
david
-- 
David H. Wolfskill                              david_at_catwhisker.org
There's no point in asking Trump "Sir, have you no decency?" -- it is
already well established that neither he nor his enablers have any.

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