> > > Log Message:
> > > Add
> > > options         MCLSHIFT=12
> > > in order to avoid a copy when a mbuf cluster has to be sent to a domU
> > > (which is the common case when the packet comes from a physical network
> > > interface).
> > 
> > i doubt if it's a reasonable value for this "GENERIC" kernel.
> > it makes mclsize dominant about socket buffer calculation, doesn't it?
> 
> Can you give more details ? I don't understand what you mean here.

sbreserve() sets sb_mbmax to (sb_hiwat * 2).
given mtu=1500 and mclsize=4096, as mclsize > (mtu * 2),
now sbspace() likely takes care of sb_mbmax rather than sb_hiwat
even for bulk transfer.

YAMAMOTO Takashi