Messages in this thread | | | From | Mark_H_Johnson@raytheon ... | Subject | Re: Real-Time Preemption, comparison to 2.6.10-mm1 | Date | Wed, 5 Jan 2005 16:58:38 -0600 |
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> Do you have a simple way of triggering and trapping the starvation? That > of course is probably asking for a lot. :)
What I have been doing is now recorded as bug #3997 at http://bugme.osdl.org/show_bug.cgi?id=3997 Running latencytest has the advantage of generating some charts that I can show others how well (or poorly) the system runs.
I just rebooted in SMP and did a few other tests with the following steps that should be simpler to set up and run.
[1] Create cpu_test.c as follows:
#define LOOPS 100000000 int main() { int u, v, k, l; for (v=0; v<100; v++) { for (u=0; u<LOOPS; u++) { k += 1; if (!(u%100)) { l += 1; k = 0; } } } return k; }
On my 866 Mhz Pentium III, it runs for about 3 minutes, 45 seconds. Adjust the outer loop in the code if you need to run shorter or longer. I would not run more than 5 minutes - you should easily get the symptom before then. This also puts a limit of how long you have to wait if the system gets "stuck" and does not respond to your keyboard or mouse.
[2] Build the application gcc -o cpu_test cpu_test.c
[3] On a two CPU system (or repeat this step N-1 times for your N cpu system). Run in a separate window... chrt -f 10 ./cpu_test
[4] In a separate window... nice ./cpu_test
At this point, you should have the system 100% utilized with N-1 real time applications & 1 nice application. I used top to confirm this result.
[5] In a separate window do one or more of the following: a. head -c $1 /dev/zero >tmpfile (replacing $1 with about 1.5x your physical memory size - this is my "disk write" test) b. cp tmpfile tmpfile2 (this is my "disk copy" test) c. cat tmpfile tmpfile2 >/dev/null (this is my "disk read" test) delete the files when done.
It appears (at least on my system) that disk I/O triggers the problem more than the other tests (x11perf, top [with no delay]).
I was however in an odd situation [just before I sent this message] where it appeared that the disk copy was OK but I could not type on any of my windows - mouse entries were OK but not the keyboard. That may be a different variant of my "starvation problem".
--Mark
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