From: David Miller <davem@davemloft.net>
To: lachlan.andrew@gmail.com
Cc: ilpo.jarvinen@helsinki.fi, netdev@vger.kernel.org, quetchen@caltech.edu
Subject: Re: [RFC PATCH net-2.6.25 uncompilable] [TCP]: Avoid breaking GSOed skbs when SACKed one-by-one
Date: Wed, 12 Dec 2007 07:11:36 -0800 (PST) [thread overview]
Message-ID: <20071212.071136.26499607.davem@davemloft.net> (raw)
In-Reply-To: <aa7d2c6d0712111614k2832f51axa8bc9736ac7ec796@mail.gmail.com>
From: "Lachlan Andrew" <lachlan.andrew@gmail.com>
Date: Tue, 11 Dec 2007 16:14:36 -0800
> This thread started because TCP processing interferes with RTT
> estimation. This problem would be eliminated if time-stamping were
> done as soon as the packet comes off the NIC.
We don't do that because such timestamping is too expensive.
It used to be the case that we did this, but we stopped doing
that a long time ago.
On x86 for example, timestamping can involve touching a slow
I/O device to read the timestamp. We do not want to do that
for every packet.
Also, we timestamp differently for TCP, the global high
resolution timestamp is overkill for this purpose.
Really, this is a silly idea and would only be a bandaid
for the problem at hand, that TCP input processing is
too expensive in certain circumstances.
next prev parent reply other threads:[~2007-12-12 15:11 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <aa7d2c6d0711261023m3d2dd850o76a8f44aef022f39@mail.gmail.com>
[not found] ` <001001c83063$9adbc9d0$d5897e82@csp.uiuc.edu>
2007-11-28 23:47 ` [PATCH] tcp-illinois: incorrect beta usage Stephen Hemminger
2007-11-29 0:25 ` Lachlan Andrew
2007-11-29 0:43 ` Stephen Hemminger
2007-11-29 5:26 ` Shao Liu
2007-12-03 22:52 ` [RFC] TCP illinois max rtt aging Stephen Hemminger
2007-12-03 23:06 ` Lachlan Andrew
2007-12-03 23:59 ` Shao Liu
2007-12-04 0:32 ` Stephen Hemminger
2007-12-04 1:23 ` Lachlan Andrew
2007-12-04 8:37 ` Ilpo Järvinen
2007-12-07 3:27 ` Lachlan Andrew
2007-12-07 11:05 ` Ilpo Järvinen
2007-12-07 12:41 ` David Miller
2007-12-07 13:05 ` Ilpo Järvinen
2007-12-07 18:27 ` Ilpo Järvinen
2007-12-08 1:32 ` David Miller
2007-12-11 11:59 ` [RFC PATCH net-2.6.25 uncompilable] [TCP]: Avoid breaking GSOed skbs when SACKed one-by-one (Was: Re: [RFC] TCP illinois max rtt aging) Ilpo Järvinen
2007-12-11 12:32 ` [RFC PATCH net-2.6.25 uncompilable] [TCP]: Avoid breaking GSOed skbs when SACKed one-by-one David Miller
2007-12-12 0:14 ` Lachlan Andrew
2007-12-12 15:11 ` David Miller [this message]
2007-12-12 23:35 ` Lachlan Andrew
2007-12-12 23:38 ` David Miller
2007-12-13 0:00 ` Stephen Hemminger
2007-12-15 9:51 ` SACK scoreboard (Was: Re: [RFC PATCH net-2.6.25 uncompilable] [TCP]: Avoid breaking GSOed skbs when SACKed one-by-one) Ilpo Järvinen
2008-01-08 7:36 ` SACK scoreboard David Miller
2008-01-08 12:12 ` Ilpo Järvinen
2008-01-09 7:58 ` David Miller
2008-01-08 16:51 ` John Heffner
2008-01-08 22:44 ` David Miller
2008-01-09 1:34 ` Lachlan Andrew
2008-01-09 6:35 ` David Miller
2008-01-09 2:25 ` Andi Kleen
2008-01-09 4:27 ` John Heffner
2008-01-09 6:41 ` David Miller
2008-01-09 14:56 ` John Heffner
2008-01-09 18:14 ` SANGTAE HA
2008-01-09 18:23 ` John Heffner
2008-01-09 12:55 ` Ilpo Järvinen
2008-01-09 6:39 ` David Miller
2008-01-09 7:03 ` Andi Kleen
2008-01-09 7:16 ` David Miller
2008-01-09 9:47 ` Evgeniy Polyakov
2008-01-09 14:02 ` Andi Kleen
2007-11-29 14:12 ` [PATCH] tcp-illinois: incorrect beta usage Herbert Xu
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