Filesystem operations slower in 13.0 than 12.2

[Adrian Chadd]

On Mon, 15 Mar 2021 at 14:58, Kevin Oberman <rkoberman at gmail.com> wrote:

> >
> > It appears that the messages are associated with reading
> > the disk(s), not directly with writing them, where the
> > reads take more than "hz * 20" time units to complete.
> > (I'm looking at main (14) code.) What might contribute
> > to the time taken for the pending read(s)?
> >
> The reference to hz * 20 woke up a few sleeping memory cells. I forgot that
> I cleaned up my loader.conf. It was largely a copy of the one on my
> decade-old T520. I commented out "kern.hz=100". I don't recall the details,
> but I think it was actually from an even older system, my T42 from before I
> retired.
>
> In any case, restoring this setting has greatly improved the situation. I
> now have really bad disk I/O performance on large disk to disk activity
> (untarring the firefox distro) instead of terrible performance and the
> system freezes have vanished, though I do see pauses in response to clicks
> or text entry, but the display remains active and the pauses are short... 1
> to 15 seconds, I'd guess. No, I have no idea what this indicates.

... which drive controller is this? Is it just a laptop ATA disk?

> I'm still not seeing the performance I was seeing back in February when 40
> MB/s for extended intervals was common and I once untarred firefox.tar.gz2
> in under a minute and performance seldom dropped below 1.4 MB/s.

Did you find a resolution?  I wonder if setting kern.hz is kicking
some process(es) to get some time more frequently due to bugs
elsewhere in the system (interrupts, IPI handling, wake-ups, etc)



-adrian