On Sat, 31 Dec 2005 17:37:11 +0100
Mike Galbraith <[email protected]> wrote:
> Strange. Using the exact same arguments, I do see some odd bouncing up to
> high priorities, but they spend the vast majority of their time down at 25.
Mmmm... to make it more easly reproducible I've enlarged the sleep time
(1 microsecond is likely to be rounded too much and give different
results on different hardware/kernel/config...).
Compile this _without_ optimizations and try again:
------------------------------------------------
#include <stdlib.h>
#include <unistd.h>
char buf[1024];
static void burn_cpu(unsigned int x)
{
int i;
for (i=0; i < x; ++i)
buf[i%sizeof(buf)] = (x-i)*3;
}
int main(int argc, char **argv)
{
unsigned long burn;
if (argc != 2)
return 1;
burn = (unsigned long)atoi(argv[1]);
if (!burn)
return;
while(1) {
burn_cpu(burn*1000);
usleep(10000);
}
return 0;
}
-----------------------------------------
With "./a.out 3000" (and 2.6.15-rc7-rt1) I get this:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
5485 paolo 15 0 2396 320 252 R 62.7 0.1 0:09.77 a.out
Try different values: 1000, 2000, 3000 ... are you able to reproduce it
now?
If yes, try to start 2 of them with something like this:
"./a.out 3000 & ./a.out 3161"
so they are NOT syncronized and they use almost all the CPU time:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
5582 paolo 16 0 2396 320 252 S 45.7 0.1 0:05.52 a.out
5583 paolo 15 0 2392 320 252 S 45.7 0.1 0:05.49 a.out
This is the bad situation I hate: some cpu-eaters that eat all the CPU
time BUT have a really good priority only because they sleeps a bit.
--
Paolo Ornati
Linux 2.6.15-rc7-rt1 on x86_64
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