Much improved sosend_*() functions

[John-Mark Gurney]

Randall Stewart wrote this message on Fri, Sep 29, 2006 at 16:55 -0400:
> Mike Silbersack wrote:
> >On Fri, 29 Sep 2006, Andre Oppermann wrote:
> >
> >
> >>over it an copies the data into the mbufs by using uiomove().  
> >>sosend_dgram()
> >>and sosend_generic() are change to use m_uiotombuf() instead of 
> >>sosend_copyin().
> >
> >
> >Can you do some UDP testing with 512b, 1K, 2K, 4K, 8K, and 16K packets to
> >see if performance changes there as well?
> 
> Hmm.. I would think 512b and 1K will not show any
> improvement.. since they would probably end up either
> in an mbuf chain.. or a single 2k (or maybe 4k) cluster..
> ... quite a waste.. now if we had 512b and 1k clusters that
> would be cool...
> 
> In fact I have always thought we should:
> 
> a) have no data portion in an mbuf.. just pointers i.e. always
>    an EXT
> 
> b) Have a 256/512 and 1k cluster too..
> 
> This would allow copy by reference no matter what size si
> being sent...

IMO it's quite a waste of memory the way we have thigns now, though
w/ TSO it'll change things...

w/ 512 byte mbuf and a 2k cluster just to store just 1514 bytes of data,
that's only 60% effeciency wrt to memory usage...  so, we currently
waste 40% of memory allocated to mbufs+clusters...  Even reducing
mbufs back to 128 or 256 would be a big help, though IPSEC I believe
would have issues...

Hmmm.. If we switched clusters to 1536 bytes in size, we'd be able to
fit 8 in 12k (though I guess for 8k page boxes we'd do 16 in 24k)...  The
only issue w/ that would be that a few of the clusters would possibly
split page boundaries...  How much this would effect performance would
be an interesting question to answer...

-- 
  John-Mark Gurney				Voice: +1 415 225 5579

     "All that I will do, has been done, All that I have, has not."