mbuf leak with SMP and debug.mpsafenet=1

[Brian Fundakowski Feldman]

On Tue, Oct 19, 2004 at 06:20:37PM -0400, Andrew Gallatin wrote:
> 
> Robert Watson writes:
>  > 
>  > Yeah -- I've been trying to avoid committing this patch since atomic
>  > operations hurt the P4 quite a bit more than one would hope.  We already
>  > do MPSAFE stats in UMA, so an interesting question might be whether these
>  > stats are redundant to stats already gathered and we can use them instead. 
>  > One of the theoretical advantages of mbuma is that mbufs become just
>  > another case of existing slab allocated memory resources, so I would think
>  > most of the interesting stats should be there. 
> 
> Getting the stats from uma seems like the right thing to do in the
> long run, but the atomic stats is a low-risk way to avoid bogus
> mbuf leak reports from 5.3-RELEASE users.

I ran into this last week and kept wondering how I was losing so many
mbufs, then searching the kernel for possible scenarios... finding none
finally matching up vmstat -z output with netstat -m to clue myself in.

We could really easily just add to netstat -m
warnx("value for SMP systems may be misleading; see manpage");

-- 
Brian Fundakowski Feldman                           \'[ FreeBSD ]''''''''''\
  <> green at FreeBSD.org                               \  The Power to Serve! \
 Opinions expressed are my own.                       \,,,,,,,,,,,,,,,,,,,,,,\