Re: acd(4) is no longer listed among other disk devices in vmstat(8)

In message <20040730150039.GA68176_at_dan.emsphone.com>, Dan Nelson writes:
>In the last episode (Jul 30), Poul-Henning Kamp said:
>> In message <20040730142537.GH9911_at_dan.emsphone.com>, Dan Nelson writes:
>> >> Somebody needs to fix vmstat(8), iostat(8) and systat(8) to look at the
>> >> stats inside GEOM instead of the driver stats.  It's not very hard to
>> >> change, it just takes some work.
>> >
>> >Just as long as we don't lose stats for non-disk devices like pass and
>> >sa. It might be easier to just fix acd.
>> 
>> We won't loose stats for non-disk devices.
>
>gstat doesn't print them, so I wasn't sure if GEOM even knew about them.  If
>it does, great!

OK, the long story:

It used to be that the device driver were responsible for doing the
device statistics.  These were exported to userland with a sysctl.

In GEOM we collect statistics at all providers (and optionally consumers).

At the same time I taught devstat subsystem to use shared memory
rather than sysctl to export the data to userland.  (there's a blueprints
article about this stuff in a previous Daemonnews).

The geom_disk class bridges these two, and therefore collects statitics
for both the old "per driver" and for the GEOM way.  This is wasteful
since it is the same data collected twice.

So the situation right now is that for geom disk device-drivers we
have both the old per-driver statistics which programs like
vmstat/iostat/systat presents and the per provider statistics which
gstat presents.

ACD on the other hand is a pure GEOM driver, it does not rely on
geom_disk and therefore it only exports the GEOM per-provider
statistics and does not show up in systat/vmstat/iostat.

So what needs to happen:

Teach the selection code in libdevstat some sort of syntax for
expressing which devstat entries we want to see in such a manner
that we can also show the geom provider entries. (Suggested default:
Anything with a geom-rank of one plus anything with no geom connection)
[This is perfect bikeshed material btw].

Remove the "per-driver" devstats in geom_disk.c

Anyone wanting to attack this problem:  please do so and keep the
geom_at_freebsd.org crowd in the loop.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk_at_FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.