acd lacks devstat [Was: systat -vmstat vs. acd]

[Andriy Gapon]

on 19.05.2005 13:03 Andriy Gapon said the following:
> With 4.X on ATA(PI)-only machine systat -vmstat used to show disks
> statistics for both ad and acd devices. Now, in 5.4-RELEASE, it shows
> statistics only for ad devices. If atapicam is added then statistics for
> cd and pass devices is shown as well.

I've done some investigation on this and it seems that this behavior
exists since circa introduction of geom and is present in current too.
A root cause of this behavior seems to be that acd is not treated as a
geom disk and doesn't have any devstat calls of itw own (unlike 4.X).
Btw, the same problem exists in current too.
I've found a short converstion on a close topic that happened a long
while ago:
http://www.mail-archive.com/freebsd-current@freebsd.org/msg33834.html

I would like to comment on two things:
1. the following part of that converion doesn't seem to be valid to me,
because cd device essentially has the same basic properties as acd and
that doesn't prevent it from being a geom disk:
> At any rate I wouldn't expect a CDROM to show up as a disk, unless
> it has a R/W medium formatted for random R/W inserted (which we at
> this time doesn't support).

2. even if acd can not be a geom disk (and maybe it can not be indeed),
shouldn't it have devstat bookkeeping of its own then ?

And the following question still remains:
> Should I file a PR ?


-- 
Andriy Gapon