Hi,
I would like to know about which threads will be preempted by which on my
OpenSolaris machine.
Therefore, I ran a multithreaded program "myprogram" with 32 threads on my
24-core Solaris machine. I make sure that each thread of my program has same
priority (priority zero), so that we can reduce priority inversions (saving
preemptions -- system overhead). However, I ran the following script
whoprempt.d to see who preempted myprogram threads and got the following output
Unlike what I thought, myprogram threads are preempted (for 2796 times -- last
line of the output) by the threads of same myprogram.
Could anyone explain why this happens, please?
DTrace script
==============
#pragma D option quiet
sched:::preempt
{
self->preempt = 1;
}
sched:::remain-cpu
/self->preempt/
{
self->preempt = 0;
}
sched:::off-cpu
/self->preempt/
{
/*
* If we were told to preempt ourselves, see who we ended up
giving
* the CPU to.
*/
@[stringof(args[1]->pr_fname), args[0]->pr_pri,
execname,
curlwpsinfo->pr_pri] = count();
self->preempt = 0;
}
END
{
printf("%30s %3s %30s %3s %5s\n", "PREEMPTOR",
"PRI","||","PREEMPTED", "PRI", "#");
printa("%30s %3d %30s %3d %5@d\n", @);
}
Output:
=======
PREEMPTOR PRI || PREEMPTED PRI #
dtrace 0 || myprogram 0 1
dtrace 50 || myprogram 0 1
sched -1 || myprogram 0 1
myprogram 0 || dtrace 0 1
....
.....
nscd 59 || myprogram 0 4
sendmail 59 || myprogram 0 4
sched 60 || myprogram 0 92
sched 98 || myprogram 0 272
sched 99 || myprogram 0 2110
myprogram 0 || myprogram 0 2796
--
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