Add option to allow single threading of sched domains
Large sched domains can be very expensive to scan. Add an option
SD_SERIALIZE to the sched domain flags. If that flag is set then
we make sure that no other such domain is being balanced.
Signed-off-by: Christoph Lameter <[email protected]>
Index: linux-2.6.19-rc5-mm1/include/asm-ia64/topology.h
===================================================================
--- linux-2.6.19-rc5-mm1.orig/include/asm-ia64/topology.h 2006-11-14 14:02:10.000000000 -0600
+++ linux-2.6.19-rc5-mm1/include/asm-ia64/topology.h 2006-11-14 14:03:05.969788964 -0600
@@ -101,6 +101,7 @@ void build_cpu_to_node_map(void);
.flags = SD_LOAD_BALANCE \
| SD_BALANCE_EXEC \
| SD_BALANCE_FORK \
+ | SD_SERIALIZE \
| SD_WAKE_BALANCE, \
.last_balance = jiffies, \
.balance_interval = 64, \
Index: linux-2.6.19-rc5-mm1/include/linux/sched.h
===================================================================
--- linux-2.6.19-rc5-mm1.orig/include/linux/sched.h 2006-11-14 14:02:10.000000000 -0600
+++ linux-2.6.19-rc5-mm1/include/linux/sched.h 2006-11-14 14:03:05.988344844 -0600
@@ -647,6 +647,7 @@ enum idle_type
#define SD_SHARE_CPUPOWER 128 /* Domain members share cpu power */
#define SD_POWERSAVINGS_BALANCE 256 /* Balance for power savings */
#define SD_SHARE_PKG_RESOURCES 512 /* Domain members share cpu pkg resources */
+#define SD_SERIALIZE 1024 /* Only a single load balancing instance */
#define BALANCE_FOR_MC_POWER \
(sched_smt_power_savings ? SD_POWERSAVINGS_BALANCE : 0)
Index: linux-2.6.19-rc5-mm1/include/linux/topology.h
===================================================================
--- linux-2.6.19-rc5-mm1.orig/include/linux/topology.h 2006-11-14 14:02:10.000000000 -0600
+++ linux-2.6.19-rc5-mm1/include/linux/topology.h 2006-11-14 14:03:06.000064348 -0600
@@ -194,7 +194,8 @@
.wake_idx = 0, /* unused */ \
.forkexec_idx = 0, /* unused */ \
.per_cpu_gain = 100, \
- .flags = SD_LOAD_BALANCE, \
+ .flags = SD_LOAD_BALANCE \
+ | SD_SERIALIZE, \
.last_balance = jiffies, \
.balance_interval = 64, \
.nr_balance_failed = 0, \
Index: linux-2.6.19-rc5-mm1/kernel/sched.c
===================================================================
--- linux-2.6.19-rc5-mm1.orig/kernel/sched.c 2006-11-14 14:03:01.000000000 -0600
+++ linux-2.6.19-rc5-mm1/kernel/sched.c 2006-11-14 14:03:26.749455649 -0600
@@ -2883,6 +2883,7 @@ static void update_load(struct rq *this_
*
* Balancing parameters are set up in arch_init_sched_domains.
*/
+static spinlock_t balancing;
static void run_rebalance_domains(struct softirq_action *h)
{
@@ -2912,6 +2913,11 @@ static void run_rebalance_domains(struct
if (unlikely(!interval))
interval = 1;
+ if (sd->flags & SD_SERIALIZE) {
+ if (!spin_trylock(&balancing))
+ goto out;
+ }
+
if (time_after_eq(jiffies, sd->last_balance + interval)) {
if (load_balance(this_cpu, this_rq, sd, idle)) {
/*
@@ -2923,6 +2929,9 @@ static void run_rebalance_domains(struct
}
sd->last_balance = jiffies;
}
+ if (sd->flags & SD_SERIALIZE)
+ spin_unlock(&balancing);
+out:
if (time_after(next_balance, sd->last_balance + interval))
next_balance = sd->last_balance + interval;
}
@@ -6986,6 +6996,7 @@ void __init sched_init(void)
#ifdef CONFIG_RT_MUTEXES
plist_head_init(&init_task.pi_waiters, &init_task.pi_lock);
+ spin_lock_init(&balancing);
#endif
/*
Index: linux-2.6.19-rc5-mm1/include/asm-i386/topology.h
===================================================================
--- linux-2.6.19-rc5-mm1.orig/include/asm-i386/topology.h 2006-11-14 14:02:10.000000000 -0600
+++ linux-2.6.19-rc5-mm1/include/asm-i386/topology.h 2006-11-14 14:03:06.055731993 -0600
@@ -89,6 +89,7 @@ static inline int node_to_first_cpu(int
.flags = SD_LOAD_BALANCE \
| SD_BALANCE_EXEC \
| SD_BALANCE_FORK \
+ | SD_SERIALIZE \
| SD_WAKE_BALANCE, \
.last_balance = jiffies, \
.balance_interval = 1, \
Index: linux-2.6.19-rc5-mm1/include/asm-powerpc/topology.h
===================================================================
--- linux-2.6.19-rc5-mm1.orig/include/asm-powerpc/topology.h 2006-11-14 14:02:10.000000000 -0600
+++ linux-2.6.19-rc5-mm1/include/asm-powerpc/topology.h 2006-11-14 14:03:06.068428123 -0600
@@ -59,6 +59,7 @@ extern int pcibus_to_node(struct pci_bus
| SD_BALANCE_EXEC \
| SD_BALANCE_NEWIDLE \
| SD_WAKE_IDLE \
+ | SD_SERIALIZE \
| SD_WAKE_BALANCE, \
.last_balance = jiffies, \
.balance_interval = 1, \
Index: linux-2.6.19-rc5-mm1/include/asm-x86_64/topology.h
===================================================================
--- linux-2.6.19-rc5-mm1.orig/include/asm-x86_64/topology.h 2006-11-14 14:02:10.000000000 -0600
+++ linux-2.6.19-rc5-mm1/include/asm-x86_64/topology.h 2006-11-14 14:03:06.082100878 -0600
@@ -47,6 +47,7 @@ extern int __node_distance(int, int);
.flags = SD_LOAD_BALANCE \
| SD_BALANCE_FORK \
| SD_BALANCE_EXEC \
+ | SD_SERIALIZE \
| SD_WAKE_BALANCE, \
.last_balance = jiffies, \
.balance_interval = 1, \
-
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