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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?
- To: Adrian Chadd <adrian_(_at_)_freebsd_(_dot_)_org>
- Subject: Re: samba performance on 1Gig link: how to replace black magic with science? And why TCP windows scaling is not in play?
- From: "Lev A. Serebryakov" <lev_(_at_)_serebryakov_(_dot_)_spb_(_dot_)_ru>
- Date: Thu, 05 Jun 2008 15:22:00 +0400
- Cc: net_(_at_)_freebsd_(_dot_)_org
Adrian Chadd wrote:
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!
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.
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?
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
// Lev Sserebryakov
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