From: David Miller <davem@davemloft.net>
To: alexandre.sidorenko@hp.com
Cc: shemminger@vyatta.com, jarkao2@gmail.com, netdev@vger.kernel.org
Subject: Re: An inconsistency/bug in ingress netem timestamps
Date: Wed, 15 Apr 2009 16:41:42 -0700 (PDT) [thread overview]
Message-ID: <20090415.164142.193730680.davem@davemloft.net> (raw)
In-Reply-To: <200904151700.59906.alexandre.sidorenko@hp.com>
From: Alex Sidorenko <alexandre.sidorenko@hp.com>
Date: Wed, 15 Apr 2009 17:00:59 -0400
> the timestamps change depending on whether there are any ptype_all handlers
> registered. Just starting tcpdump changes the behaviour, this probably
> means 'inconsistent' ?
It changes whether there is a "timestamp user" and packet sniffers are
currently defined as such as user.
The argument is whether the overhead of making this type of use
a "timestamp user" is warranted or not.
Turning on timestamps is heavily optimized like this because taking
the timestamp on every packet is extremely expensive, especially
on large classes of x86 systems.
Therefore if we make changes here, they have to have a very specific
and limited scope in order to avoid turning this expensive operation
on when it's not really necessary.
next prev parent reply other threads:[~2009-04-15 23:41 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-04-13 19:50 An inconsistency/bug in ingress netem timestamps Alex Sidorenko
2009-04-15 19:50 ` Jarek Poplawski
2009-04-15 20:10 ` Alex Sidorenko
2009-04-15 20:26 ` Jarek Poplawski
2009-04-15 20:29 ` Stephen Hemminger
2009-04-15 21:00 ` Alex Sidorenko
2009-04-15 23:41 ` David Miller [this message]
2009-04-16 10:10 ` David Miller
2009-04-16 12:09 ` Alex Sidorenko
2009-04-16 21:48 ` Jarek Poplawski
2009-04-17 12:04 ` David Miller
2009-04-17 16:50 ` Alex Sidorenko
2009-04-17 20:08 ` [PATCH] " Jarek Poplawski
2009-04-20 9:15 ` David Miller
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