netdev - Re: BW regression after "tcp: refine TSO autosizing"

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Date:	Tue, 20 Jan 2015 11:14:37 -0800
From:	Rick Jones <rick.jones2@...com>
To:	Eric Dumazet <eric.dumazet@...il.com>,
	Dave Taht <dave.taht@...il.com>
CC:	Eyal Perry <eyalpe@...lanox.com>,
	Yuchung Cheng <ycheng@...gle.com>,
	Neal Cardwell <ncardwell@...gle.com>,
	Eyal Perry <eyalpe@....mellanox.co.il>,
	Or Gerlitz <gerlitz.or@...il.com>,
	Linux Netdev List <netdev@...r.kernel.org>,
	Amir Vadai <amirv@...lanox.com>,
	Yevgeny Petrilin <yevgenyp@...lanox.com>,
	Saeed Mahameed <saeedm@...lanox.com>,
	Ido Shamay <idos@...lanox.com>, Amir Ancel <amira@...lanox.com>
Subject: Re: BW regression after "tcp: refine TSO autosizing"


>> Are you saying that at long last, delayed acks as we knew them are
>> dead, dead, dead?
>
> Sorry, I can not parse what you are saying.
>
> In case you missed it, it has nothing to do with delayed ACK but GRO on
> receiver.

Dave - assuming I've interpreted Eric's comments correctly, I believe 
the answer to your question is No.  Your desire for a world brimming 
with ack-every-other purity has not been fulfilled :)

However, the engineers formerly at Mentat are probably pleased that a 
functional near-equivalent to their ACK avoidance heuristic has ended-up 
being implemented and tacitly accepted, albeit by the back door :)


>>> DUMP_TCP_INFO=1 ./netperf -H remote -T2,2 -t TCP_STREAM -l 20
>>> MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to remote () port 0 AF_INET : cpu bind
>>> rto=201000 ato=0 pmtu=1500 rcv_ssthresh=29200 rtt=67 rttvar=6 snd_ssthresh=263 cwnd=265 reordering=3 total_retrans=4569 ca_state=0
>>
>> The above statistics are not dumped by my netperf, and look extremely
>> desirable to capture in netperf-wrapper. This is a script parsing some
>> other kernel data at the conclusion of the run? or a better netperf?
>
> Thats a 3 lines patch in netperf actually.

More stuff to pull from a TCP_INFO call I presume?  Feel free to drop me 
a patch, though I'd probably want it to be in the guise of the omni 
output selectors.

happy benchmarking,

rick
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