samba performance on 1Gig link: how to replace black magic with science? And why TCP windows scaling is not in play?

[Lev A. Serebryakov]

Adrian Chadd wrote:

> Figure out why window scaling isn't working - look at the options
> being negotiated (use tcpdump) and try to figure out which side isn't
> offering or is rejecting window size scaling negotiation.
   FreeBSD suggest scaling 9, Windows -- scaling 0. After that FreeBSD 
uses scaling, but windows is 49152 (scaled! 0x0060 in header!) always 
from FreeBSD to Win due to SO_RCVBUF=49152. Without this option window 
is 130560, but speed is MUCH worse!

> CIFS isn't the same profile as iperf/etc - its not just shovelling raw
> data down the socket, there's a whole protocol involved in scheduling
> what to transfer. Latency in handling commands screws your
> performance..
   But how this "magic values" in socket buffers can be explained? As 
far as I know, there are "big read/big write" commands in CIFS, which 
allows use more than 64K in one operation?

-- 
// Lev Sserebryakov