From: Lennert Buytenhek <buytenh@wantstofly.org>
To: Ben Greear <greearb@candelatech.com>
Cc: Robert Olsson <Robert.Olsson@data.slu.se>,
hadi@cyberus.ca, netdev@oss.sgi.com
Subject: Re: inter-packet gap in pktgen
Date: Wed, 8 Dec 2004 08:38:58 +0100 [thread overview]
Message-ID: <20041208073858.GA4027@xi.wantstofly.org> (raw)
In-Reply-To: <41B632F3.1090104@candelatech.com>
On Tue, Dec 07, 2004 at 02:47:15PM -0800, Ben Greear wrote:
> >By tweaking the 'ipg' parameter I can generate pretty much any packet rate
> >I want, as long as I set ipg=(1e9/rate)-496 instead of something possibly
> >more straightforward.
>
> That 496 will also change with load on the system, at least on average. I
> dealt with this by having a user-space app sample the rate and adjust the
> ipg to keep the average rate where I want it.
>
> So, I'd suggest leaving the ipg as it is, and use external tools to get
> the exact pps that you are looking for.
Just because it's possible that way doesn't mean that it's the only
way or even _the_ way of doing it.
Another option is:
next_tx = get_time_in_ns();
while (--count) {
tx_packet();
next_tx += 1e9/intended_pps;
nanospin(next_tx - get_time_in_ns());
}
This should be relatively independent of system load. OK, I know,
time to show some code.
--L
next prev parent reply other threads:[~2004-12-08 7:38 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-12-07 22:25 inter-packet gap in pktgen Lennert Buytenhek
2004-12-07 22:47 ` Ben Greear
2004-12-08 7:38 ` Lennert Buytenhek [this message]
2004-12-08 10:21 ` Robert Olsson
2004-12-08 11:15 ` Lennert Buytenhek
2004-12-08 19:32 ` Ben Greear
2004-12-10 22:29 ` Lennert Buytenhek
2004-12-10 23:01 ` Ben Greear
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