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- Implement much more intelligent ipi sending. This algorithm tries to

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minimize IPIs and rescheduling when scheduling like tasks while keeping
   latency low for important threads.
   1) An idle thread is running.
   2) The current thread is worse than realtime and the new thread is
      better than realtime.  Realtime to realtime doesn't preempt.
   3) The new thread's priority is less than the threshold.
This commit is contained in:
Jeff Roberson 2007-01-25 23:51:59 +00:00
parent 45a5e03456
commit fc3a97dcb7
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=166247
1 changed files with 23 additions and 11 deletions
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34
sys/kern/sched_ule.c
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@ -700,31 +700,43 @@ tdq_idled(struct tdq *tdq)
static void
tdq_notify(struct td_sched *ts)
{
struct thread *td;
struct thread *ctd;
struct pcpu *pcpu;
int prio;
int cpri;
int pri;
int cpu;
prio = ts->ts_thread->td_priority;
cpu = ts->ts_cpu;
pri = ts->ts_thread->td_priority;
pcpu = pcpu_find(cpu);
td = pcpu->pc_curthread;
ctd = pcpu->pc_curthread;
cpri = ctd->td_priority;
/*
* If our priority is not better than the current priority there is
* nothing to do.
*/
if (prio > td->td_priority)
if (pri > cpri)
return;
/* Always set NEEDRESCHED. */
td->td_flags |= TDF_NEEDRESCHED;
/*
* IPI if we exceed the threshold or if the target cpu is running an
* idle thread.
* Always IPI idle.
*/
if (prio > ipi_thresh && td->td_priority < PRI_MIN_IDLE)
if (cpri > PRI_MIN_IDLE)
goto sendipi;
/*
* If we're realtime or better and there is timeshare or worse running
* send an IPI.
*/
if (pri < PRI_MAX_REALTIME && cpri > PRI_MAX_REALTIME)
goto sendipi;
/*
* Otherwise only IPI if we exceed the threshold.
*/
if (pri > ipi_thresh)
return;
if (td->td_priority < PRI_MIN_IDLE) {
sendipi:
ctd->td_flags |= TDF_NEEDRESCHED;
if (cpri < PRI_MIN_IDLE) {
if (ipi_ast)
ipi_selected(1 << cpu, IPI_AST);
else if (ipi_preempt)