MBUF statistics

[Robert Watson]

On Tue, 15 Feb 2005, Borja Marcos wrote:

> 	Looking at the mbuf statistics available in FreeBSD 4 and
> FreeBSD 5 I can see that the statistics available in FreeBSD 5 are,
> surprisingly, much less comprehensive. Is there any other place where I
> can find out how many mbuf requests have been done, how many of them
> have waited, how many have failed, etc? 
> 
> 	I think that it's an interesting resource to graph in a Orca
> performance monitor for FreeBSD. 

This statistic appears to have been lost during the conversion to UMA
allocating mbufs.  I probably won't get to it this week, but I'll try to
get that statistic back in the mix in the next week or two. Unfortunately,
it may break the user<->kernel ABI for monitoring applications, since
there appear to be no spare fields in the mbstat structure.  What I'd like
to do, actually, is add tracking of allocation failures to UMA, and then
use UMA statistics to generate the mbuf output of netstat rather than a
separate API.  This would also eliminate SMP races present in the
maintenance of mbuf statistics (they can "drift" on SMP boxes right now).

Robert N M Watson