Author: marius
Date: Thu Oct 6 11:48:13 2011
New Revision: 226057
URL: http://svn.freebsd.org/changeset/base/226057
Log:
- Currently, sched_balance_pair() may cause a CPU to send an IPI_PREEMPT to
itself, which sparc64 hardware doesn't support. One way to solve this
would be to directly call sched_preempt() instead of issuing a self-IPI.
However, quoting jhb@:
"On the other hand, you can probably just skip the IPI entirely if we are
going to send it to the current CPU. Presumably, once this routine
finishes, the current CPU will exit softlock (or will do so "soon") and
will then pick the next thread to run based on the adjustments made in
this routine, so there's no need to IPI the CPU running this routine
anyway. I think this is the better solution. Right now what is probably
happening on other platforms is as soon as this routine finishes the CPU
processes its self-IPI and causes mi_switch() which will just switch back
to the softclock thread it is already running."
- With r226054 and the the above change in place, sparc64 now no longer is
incompatible with ULE and vice versa. However, powerpc/E500 still is.
Submitted by: jhb
Reviewed by: jeff
Modified:
head/sys/kern/sched_ule.c
Modified: head/sys/kern/sched_ule.c
==============================================================================
--- head/sys/kern/sched_ule.c Thu Oct 6 11:20:21 2011 (r226056)
+++ head/sys/kern/sched_ule.c Thu Oct 6 11:48:13 2011 (r226057)
@@ -76,7 +76,7 @@ dtrace_vtime_switch_func_t dtrace_vtime_
#include <machine/cpu.h>
#include <machine/smp.h>
-#if defined(__sparc64__)
+#if defined(__powerpc__) && defined(E500)
#error "This architecture is not currently compatible with ULE"
#endif
@@ -839,6 +839,7 @@ sched_balance_pair(struct tdq *high, str
int low_load;
int moved;
int move;
+ int cpu;
int diff;
int i;
@@ -860,10 +861,14 @@ sched_balance_pair(struct tdq *high, str
for (i = 0; i < move; i++)
moved += tdq_move(high, low);
/*
- * IPI the target cpu to force it to reschedule with the new
- * workload.
+ * In case the target isn't the current cpu IPI it to force a
+ * reschedule with the new workload.
*/
- ipi_cpu(TDQ_ID(low), IPI_PREEMPT);
+ cpu = TDQ_ID(low);
+ sched_pin();
+ if (cpu != PCPU_GET(cpuid))
+ ipi_cpu(cpu, IPI_PREEMPT);
+ sched_unpin();
}
tdq_unlock_pair(high, low);
return (moved);
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