DragonFly BSD
DragonFly kernel List (threaded) for 2005-10
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Re: ftp runs slower on CPU 1

From: "Simon 'corecode' Schubert" <corecode@xxxxxxxxxxxx>
Date: Wed, 19 Oct 2005 11:50:53 +0200

Oliver Fromme wrote:
Phungte <phungte@xxxxxxxxx> wrote:
 > I am running a performance test on a dual cpu machine, with DragonFly
 > 1.3.7-DEVELOPMENT #2.
 > The machine runs as ftp server.
 > When ever the tcp thread runs on CPU0, the speed of the transfer is
 > ~90MB/sec.
 > If the tcpu thread runs on CPU1, the speed is down to less than 40MB/sec.

My guess is that interrupts are serviced on one CPU only.
If your server process happens to run on the same CPU, it
has to share it with interrupt processing.  If it runs on
the other CPU, then it gets its performance exclusively.
It would be interesting how enabling or disabling polling
influences your results.

Or maybe it's right the other way around: If the interrupts get served at the same CPU, then the packet data will be cached already (from the tcp thread selection code).

We really need to do some benchmarks on that.


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