Re: TCP, and clamping MSS..?
Re: TCP, and clamping MSS..?
- Subject: Re: TCP, and clamping MSS..?
- From: Vincent Lubet <email@hidden>
- Date: Thu, 11 Jan 2007 10:50:11 -0800
On Jan 11, 2007, at 6:16 AM, Andrew Gallatin wrote:
Thanks Vince.. I've filed problem id 4919145.
We got it.
FWIW, it looks like the MSS clamping code was removed sometime between
10.2 and 10.3. I've never really understood why it helps so much.
This isn't just my NIC that it helps for. See the thread starting at
http://lists.freebsd.org/pipermail/freebsd-net/2004-January/
002594.html
where I actually proposed removing it, and found that it really did
help!
Do you have any intuition on why keeping things nicely aligned helps
so much? Linux, on the same hardware, does not need to clamp the MTU,
and easily maxes out the 10GbE link with far lower CPU utilization.
Is the BSD stack just that much more sensitive to alignment?
I'm not sure why it's so sensitive, may be it has something do with
the mbuf
allocator.
Vincent
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