From: Eric Dumazet <eric.dumazet@gmail.com>
To: Alexander Zimmermann <alexander.zimmermann@comsys.rwth-aachen.de>
Cc: Yuchung Cheng <ycheng@google.com>,
Hagen Paul Pfeifer <hagen@jauu.net>,
netdev <netdev@vger.kernel.org>, Hannemann Arnd <arnd@arndnet.de>,
Lukowski Damian <damian@tvk.rwth-aachen.de>
Subject: Re: [PATCH] tcp: bound RTO to minimum
Date: Thu, 25 Aug 2011 10:26:45 +0200 [thread overview]
Message-ID: <1314260805.2387.11.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC> (raw)
In-Reply-To: <4033BFEE-C432-4D94-8372-BA166AF2AA26@comsys.rwth-aachen.de>
Le jeudi 25 août 2011 à 09:28 +0200, Alexander Zimmermann a écrit :
> Hi Eric,
>
> Am 25.08.2011 um 07:28 schrieb Eric Dumazet:
> > Real question is : do we really want to process ~1000 timer interrupts
> > per tcp session, ~2000 skb alloc/free/build/handling, possibly ~1000 ARP
> > requests, only to make tcp revover in ~1sec when connectivity returns
> > back. This just doesnt scale.
>
> maybe a stupid question, but 1000?. With an minRTO of 200ms and a maximum
> probing time of 120s, we 600 retransmits in a worst-case-senario
> (assumed that we get for every rot retransmission an icmp). No?
Where is asserted the "max probing time of 120s" ?
It is not the case on my machine :
I have way more retransmits than that, even if spaced by 1600 ms
07:16:13.389331 write(3, "\350F\235JC\357\376\363&\3\374\270R\21L\26\324{\37p\342\244i\304\356\241I:\301\332\222\26"..., 48) = 48
07:16:13.389417 select(7, [3 4], [], NULL, NULL) = 1 (in [3])
07:31:39.901311 read(3, 0xff8c4c90, 8192) = -1 EHOSTUNREACH (No route to host)
Old kernels where performing up to 15 retries, doing exponential backoff.
Now its kind of unlimited, according to experimental results.
next prev parent reply other threads:[~2011-08-25 8:26 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-24 16:21 [BUG] tcp : how many times a frame can possibly be retransmitted ? Eric Dumazet
2011-08-24 19:03 ` Alexander Zimmermann
2011-08-24 19:39 ` Jerry Chu
2011-08-24 19:45 ` Eric Dumazet
2011-08-24 22:44 ` Ilpo Järvinen
2011-08-24 23:00 ` Eric Dumazet
2011-08-24 23:41 ` [PATCH] tcp: bound RTO to minimum Hagen Paul Pfeifer
2011-08-24 23:43 ` Hagen Paul Pfeifer
2011-08-25 1:50 ` Yuchung Cheng
2011-08-25 5:28 ` Eric Dumazet
2011-08-25 7:28 ` Alexander Zimmermann
2011-08-25 8:26 ` Eric Dumazet [this message]
2011-08-25 8:44 ` Alexander Zimmermann
2011-08-25 8:46 ` Arnd Hannemann
2011-08-25 9:09 ` Eric Dumazet
2011-08-25 9:46 ` Arnd Hannemann
2011-08-25 10:02 ` Eric Dumazet
2011-08-25 10:14 ` Ilpo Järvinen
2011-08-25 10:15 ` Arnd Hannemann
2011-08-25 8:56 ` [BUG] tcp : how many times a frame can possibly be retransmitted ? Ilpo Järvinen
2011-08-25 9:40 ` Eric Dumazet
2011-08-25 10:07 ` Ilpo Järvinen
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