On 25 Sep 2017, at 17:04, Stephen Hurd wrote:
Bjoern A. Zeeb wrote:
On 23 Sep 2017, at 23:46, Stephen Hurd wrote:
Bjoern A. Zeeb wrote:
On 23 Sep 2017, at 6:32, Stephen Hurd wrote:
Bjoern A. Zeeb wrote:
On 23 Sep 2017, at 1:35, Stephen Hurd wrote:
Author: shurd
Date: Sat Sep 23 01:35:14 2017
New Revision: 323942
URL: https://svnweb.freebsd.org/changeset/base/323942
Log:
Chain mbufs before passing to if_input()
Build a list of mbufs to pass to if_input() after LRO.
Results in
12% small packet forwarding rate improvement.
I not saying anything against the change, I am just saying the commit
message doesn’t describe what it does.
Can you explain what was confusing about it or propose other wording?
I'm not sure what was confusing, and I'd like to avoid similarly
confusing messages in the future.
I think it’s because I read “after LRO” as “after LRO processing
happened” which is exactly not what is happening in that case; I know
logically in the code order it’s “after LRO”.
If I understand the change correctly (and I think jtl summarised it
quite well already as well):
“In cases when LRO is disabled or LRO is not consuming the packet,
try to build an mbuf chain and pass the chain to if_input() thus
lowering the per-packet overheads (*).
For a packet forwarding case we have seen a 12% rate improvement for
small packets.”
(*) would be nice to describe them at this point so people understand
where 12% come from (e.g., function call overhead, locking overhead,
whatever ..) because that’s the reason you are doing the change.
Also I am pretty sure this works with ether_input but not so much
with fddi_input, iso88025_input, and ifdead_input is probably going
to leak as well.
Thanks for the heads up. They all seem to use m_freem(), so they
shouldn't leak.
Right. My bad.
It doesn't look like they would actually work though (except
ifdead_input of course).
Well, they’d work with a bit of packet loss I guess ;-)
/bz
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