Accounting for mbufs and clusters assigned to a socket buffer

[gnn at freebsd.org]

At Wed, 07 May 2008 06:17:48 +0300,
Giorgos Keramidas wrote:
> 
> I guess we could check *both* (m_flags & M_EXT) and m_ext.ext_type.
> 
> This won't really show how many mbufs use a classic cluster vs. a 9k
> cluster, but checking for all the m_ext.ext_types is probably going to
> look a bit ugly in a single if-check :(
> 
> We have at least EXT_CLUSTER, EXT_JUMBOP, EXT_JUMBO9, EXT_JUMBO16 and
> EXT_PACKET which may be interesting for cluster-related accounting, but
> in socketvar.h we can't really use the uma zone accounting.  I just
> noticed that the 'interesting' ext_types are conveniently short integers
> though.  Maybe we could change sb_ccnt to a small array, and then change
> 
>     if ((m)->m_flags & M_EXT) \
>         (sb)->sb_ccnt += 1;
> 
> to something like:
> 
>     if ((m)->m_flags & M_EXT && (m)->m_ext.ext_type < EXT_MBUF) \
>         (sb)->sb_ccnt[(m)->m_ext.ext_type - 1] += 1; \
> 
> With our current ext_type's
> 
> #define EXT_CLUSTER     1       /* mbuf cluster */
> #define EXT_SFBUF       2       /* sendfile(2)'s sf_bufs */
> #define EXT_JUMBOP      3       /* jumbo cluster 4096 bytes */
> #define EXT_JUMBO9      4       /* jumbo cluster 9216 bytes */
> #define EXT_JUMBO16     5       /* jumbo cluster 16184 bytes */
> #define EXT_PACKET      6       /* mbuf+cluster from packet zone */
> #define EXT_MBUF        7       /* external mbuf reference (M_IOVEC) */
> ...
> 
> the [ext_type - 1] would move the burden of parsing the ext_type at the
> place where we actually have to print something about the sb_ccnt
> counters.
> 
> Would the 'bloat' of u_int[6] for ext_type's which are unused  be too
> much to keep around?

I don't know if we want to go that far, but we could certainly try
it.  I'll keep it in mind.

Thanks,
George