Messages in this thread | | | Date | Mon, 8 Jul 2002 08:27:56 -0400 (EDT) | From | "Richard B. Johnson" <> | Subject | Re: timer queue is still influenced by network load |
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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.
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