On Wed, 3 Jul 2002, Xinwen - Fu wrote:
> Richard,
> I did a few experiments using the example (jiq, I changed jiffies
> to do_gettimeofday() ) from Linux Device
> Driver, 2nd version (p196).
>
> I have two machines m1 and m2. On m1, I run a timer queue (jiq)
> module. Then I download a big file from m1 to m2. The timings are
> different between before ftp and during ftp.
>
>
>
> It shows that
> timer queue is still not accurate. So
> the conclusion of " you're guaranteed that the queue will run at the next
> clock tick, thus eliminating latency caused by system load" is WRONG!!!
>
> What is your opinion?
Well you are guaranteed that it will run. You just don't know how fast
it will run. The bottom-half code run off the timer-queue is run with
the interrupts enabled. It can get interrupted and it may be interrupted
by network driver code that loops in ISRs, taking a large percentage
of the CPU cycles.
So, I don't think you are measuring what you think you are measuring.
Cheers,
Dick Johnson
Penguin : Linux version 2.4.18 on an i686 machine (797.90 BogoMips).
Windows-2000/Professional isn't.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Mon Jul 15 2002 - 22:00:12 EST