From: Eric Dumazet <eric.dumazet@gmail.com>
To: Tom Herbert <therbert@google.com>
Cc: netdev@vger.kernel.org
Subject: Re: Very low latency TCP for clusters
Date: Tue, 20 Jul 2010 00:03:00 +0200 [thread overview]
Message-ID: <1279576980.2458.56.camel@edumazet-laptop> (raw)
In-Reply-To: <AANLkTiniRmnwG4vT-MrQQHQjrdQ4sfOn6Uxi42Dsr8nu@mail.gmail.com>
Le lundi 19 juillet 2010 à 11:44 -0700, Tom Herbert a écrit :
> I see about 7 usecs as best number on loopback, so I believe this is
> in the ballpark. As I mentioned above, this about "best case" latency
> of a single thread, so we assume any amount of pinning or other
> customized configuration to that purpose.
Well, given I get 29 us on a ping between two machines (Gb link, no
process involved on receiver, only softirq), I really doubt we can reach
5 us on a tcp test involving a user process on both side ;)
$ ping -f -c 10000 -q 192.168.0.1
PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data.
--- 192.168.0.1 ping statistics ---
10000 packets transmitted, 10000 received, 0% packet loss, time 395ms
rtt min/avg/max/mdev = 0.029/0.032/0.434/0.010 ms, ipg/ewma 0.039/0.033
ms
On loopback, its a bit better of course, but there is no cache miss nor
scheduler involved.
$ ping -f -c 10000 -q 127.0.0.1
PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data.
--- 127.0.0.1 ping statistics ---
10000 packets transmitted, 10000 received, 0% packet loss, time 55ms
rtt min/avg/max/mdev = 0.002/0.002/0.015/0.001 ms, ipg/ewma 0.005/0.002
ms
next prev parent reply other threads:[~2010-07-19 22:03 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-19 17:05 Very low latency TCP for clusters Tom Herbert
2010-07-19 17:35 ` David Miller
2010-07-19 17:41 ` Eric Dumazet
2010-07-19 18:44 ` Tom Herbert
2010-07-19 19:27 ` David Miller
2010-07-19 22:03 ` Eric Dumazet [this message]
2010-07-19 23:37 ` Tom Herbert
2010-07-20 5:26 ` Eric Dumazet
2010-07-20 17:24 ` Rick Jones
2010-07-20 12:57 ` Brian Bloniarz
2010-07-19 18:13 ` Rick Jones
2010-07-19 18:28 ` Nivedita Singhvi
2010-07-19 19:46 ` Mitchell Erblich
2010-07-19 21:16 ` Tom Herbert
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