[Fwd: [SLE] microsecond clock timer]

Message-ID: <3A361DF7.584E043F@computer.org> Date: Tue, 12 Dec 2000 12:45:43 +0000 From: Garry Smith Subject: [Fwd: [SLE] microsecond clock timer] Whooops, wrong reply-to address. Try again!! Garry Smith wrote:

Hi Alan,

Thank you for your reply.

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I think you will find that select() uses the interval timer, so therefore select() will be subject to the same granularity problems (10ms minimum time) as I mentioned in my earlier posting.

It sounds like this is going to be a real pain :-(

The interval timer, this must be a software component in the Linux kernel, yes? The actual clock harware should be nonosecs! surely... We are talking of chips that have MHz/GHz...

I have been given a microsecond clock .dll for Windows (which I have yet to use). I do not yet know if that lives up to the microsecond requirement either.

When I have a moment I will do a comparison between the Linux (as discussed here)/Windows methods to see what happens. It will be interesting to see if Windows can manage a finer granularity.

What do other people do when they need to test (accurately) the performance of their code on Linux? I am particularily interested in timing the period that method calls take to complete

regards Garry

...

Alan Lenton

----- Original Message ----- From: "Jesse Marlin" To: "Garry Smith" Cc: Sent: Monday, December 11, 2000 3:04 PM Subject: [SLE] microsecond clock timer

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Hi all,

I am about to start doing some performance testing on a software

Garry Smith writes: project

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that I am involved with. I would like to use my version of SuSE Linux 7.0 Professional as one of the test platforms.

How can I get Linux to provide microsecond granularity when I make calls to the system clock? In otherwords, I need a microsecond clock on Linux to get accurate performance measurements of my software?

You can use select, like so:

struct timeval tv;

tv.tv_sec = 0; tv.tv_usec = 1000;

/* Sleep for a while */ select (0, NULL, NULL, NULL, &tv);

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