From: Nick Piggin <nickpiggin@yahoo.com.au>
---
25-akpm/include/linux/sched.h | 9 ++++++---
25-akpm/kernel/sched.c | 35 +++++++++++++++++++----------------
2 files changed, 25 insertions(+), 19 deletions(-)
diff -puN include/linux/sched.h~sched-damp-passive-balance include/linux/sched.h
--- 25/include/linux/sched.h~sched-damp-passive-balance 2004-04-03 15:20:55.603952496 -0800
+++ 25-akpm/include/linux/sched.h 2004-04-03 15:20:55.609951584 -0800
@@ -543,7 +543,8 @@ do { if (atomic_dec_and_test(&(tsk)->usa
#define SD_BALANCE_EXEC 2 /* Balance on exec */
#define SD_WAKE_IDLE 4 /* Wake to idle CPU on task wakeup */
#define SD_WAKE_AFFINE 8 /* Wake task to waking CPU */
-#define SD_SHARE_CPUPOWER 16 /* Domain members share cpu power */
+#define SD_WAKE_BALANCE 16 /* Perform balancing at task wakeup */
+#define SD_SHARE_CPUPOWER 32 /* Domain members share cpu power */
struct sched_group {
struct sched_group *next; /* Must be a circular list */
@@ -612,7 +613,8 @@ struct sched_domain {
.cache_nice_tries = 1, \
.per_cpu_gain = 100, \
.flags = SD_BALANCE_NEWIDLE \
- | SD_WAKE_AFFINE, \
+ | SD_WAKE_AFFINE \
+ | SD_WAKE_BALANCE, \
.last_balance = jiffies, \
.balance_interval = 1, \
.nr_balance_failed = 0, \
@@ -631,7 +633,8 @@ struct sched_domain {
.cache_hot_time = (10*1000000), \
.cache_nice_tries = 1, \
.per_cpu_gain = 100, \
- .flags = SD_BALANCE_EXEC, \
+ .flags = SD_BALANCE_EXEC \
+ | SD_WAKE_BALANCE, \
.last_balance = jiffies, \
.balance_interval = 1, \
.nr_balance_failed = 0, \
diff -puN kernel/sched.c~sched-damp-passive-balance kernel/sched.c
--- 25/kernel/sched.c~sched-damp-passive-balance 2004-04-03 15:20:55.605952192 -0800
+++ 25-akpm/kernel/sched.c 2004-04-03 15:20:55.612951128 -0800
@@ -760,25 +760,28 @@ static int try_to_wake_up(task_t * p, un
new_cpu = this_cpu; /* Wake to this CPU if we can */
/*
- * Passive load balancing. If the queues are very out of balance
- * we might as well balance here rather than the periodic load
- * balancing.
- */
- if (load > this_load + SCHED_LOAD_SCALE*2)
- goto out_set_cpu;
-
- /*
- * Migrate the task to the waking domain.
- * Do not violate hard affinity.
+ * Scan domains for affine wakeup and passive balancing
+ * possibilities.
*/
for_each_domain(this_cpu, sd) {
- if (!(sd->flags & SD_WAKE_AFFINE))
- break;
- if (task_hot(p, rq->timestamp_last_tick, sd))
- break;
+ unsigned int imbalance;
+ /*
+ * Start passive balancing when half the imbalance_pct
+ * limit is reached.
+ */
+ imbalance = sd->imbalance_pct + (sd->imbalance_pct - 100) / 2;
- if (cpu_isset(cpu, sd->span))
- goto out_set_cpu;
+ if ( ((sd->flags & SD_WAKE_AFFINE) &&
+ !task_hot(p, rq->timestamp_last_tick, sd))
+ || ((sd->flags & SD_WAKE_BALANCE) &&
+ imbalance*this_load <= 100*load) ) {
+ /*
+ * Now sd has SD_WAKE_AFFINE and p is cache cold in sd
+ * or sd has SD_WAKE_BALANCE and there is an imbalance
+ */
+ if (cpu_isset(cpu, sd->span))
+ goto out_set_cpu;
+ }
}
new_cpu = cpu; /* Could not wake to this_cpu. Wake to cpu instead */
_