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



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
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