svn commit: r322863 - head/sys/cam

[Warner Losh]

On Fri, Aug 25, 2017 at 7:35 AM, Slawa Olhovchenkov <slw at zxy.spb.ru> wrote:

> On Thu, Aug 24, 2017 at 10:11:10PM +0000, Warner Losh wrote:
>
> > Author: imp
> > Date: Thu Aug 24 22:11:10 2017
> > New Revision: 322863
> > URL: https://svnweb.freebsd.org/changeset/base/322863
> >
> > Log:
> >   Expand the latency tracking array from 1.024s to 8.192s to help track
> >   extreme outliers from dodgy drives. Adjust comments to reflect this,
> >   and make sure that the number of latency buckets match in the two
> >   places where it matters.
>
> May be up to 1min?
>

I'm not sure what additional data you'll get between "totally sucks, at
least 8s latency" and "totally sucks, at least 32s." or "totally sucks, at
least 64s" though the latter isn't possible with the default timeouts...

I'm planning on adding a 'max' latency that's self-resetting instead of
expanding the bucket upwards. I'm also contemplating expanding it down to
100us or even 10us since nda serves nvme drives which easily can be sub
100us.

Warner