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Subject[tip:sched/balancing] sched: Add SD_PREFER_SIBLING
Commit-ID:  b5d978e0c7e79a7ff842e895c85a86b38c71f1cd
Gitweb: http://git.kernel.org/tip/b5d978e0c7e79a7ff842e895c85a86b38c71f1cd
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Tue, 1 Sep 2009 10:34:33 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Fri, 4 Sep 2009 10:09:53 +0200

sched: Add SD_PREFER_SIBLING

Do the placement thing using SD flags.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Acked-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Acked-by: Gautham R Shenoy <ego@in.ibm.com>
Cc: Balbir Singh <balbir@in.ibm.com>
LKML-Reference: <20090901083825.897028974@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
include/linux/sched.h | 29 +++++++++++++++--------------
kernel/sched.c | 14 +++++++++++++-
2 files changed, 28 insertions(+), 15 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 9c96ef2..651dded 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -798,18 +798,19 @@ enum cpu_idle_type {
#define SCHED_LOAD_SCALE_FUZZ SCHED_LOAD_SCALE

#ifdef CONFIG_SMP
-#define SD_LOAD_BALANCE 1 /* Do load balancing on this domain. */
-#define SD_BALANCE_NEWIDLE 2 /* Balance when about to become idle */
-#define SD_BALANCE_EXEC 4 /* Balance on exec */
-#define SD_BALANCE_FORK 8 /* Balance on fork, clone */
-#define SD_WAKE_IDLE 16 /* Wake to idle CPU on task wakeup */
-#define SD_WAKE_AFFINE 32 /* Wake task to waking CPU */
-#define SD_WAKE_BALANCE 64 /* Perform balancing at task wakeup */
-#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 SD_WAKE_IDLE_FAR 2048 /* Gain latency sacrificing cache hit */
+#define SD_LOAD_BALANCE 0x0001 /* Do load balancing on this domain. */
+#define SD_BALANCE_NEWIDLE 0x0002 /* Balance when about to become idle */
+#define SD_BALANCE_EXEC 0x0004 /* Balance on exec */
+#define SD_BALANCE_FORK 0x0008 /* Balance on fork, clone */
+#define SD_WAKE_IDLE 0x0010 /* Wake to idle CPU on task wakeup */
+#define SD_WAKE_AFFINE 0x0020 /* Wake task to waking CPU */
+#define SD_WAKE_BALANCE 0x0040 /* Perform balancing at task wakeup */
+#define SD_SHARE_CPUPOWER 0x0080 /* Domain members share cpu power */
+#define SD_POWERSAVINGS_BALANCE 0x0100 /* Balance for power savings */
+#define SD_SHARE_PKG_RESOURCES 0x0200 /* Domain members share cpu pkg resources */
+#define SD_SERIALIZE 0x0400 /* Only a single load balancing instance */
+#define SD_WAKE_IDLE_FAR 0x0800 /* Gain latency sacrificing cache hit */
+#define SD_PREFER_SIBLING 0x1000 /* Prefer to place tasks in a sibling domain */

enum powersavings_balance_level {
POWERSAVINGS_BALANCE_NONE = 0, /* No power saving load balance */
@@ -829,7 +830,7 @@ static inline int sd_balance_for_mc_power(void)
if (sched_smt_power_savings)
return SD_POWERSAVINGS_BALANCE;

- return 0;
+ return SD_PREFER_SIBLING;
}

static inline int sd_balance_for_package_power(void)
@@ -837,7 +838,7 @@ static inline int sd_balance_for_package_power(void)
if (sched_mc_power_savings | sched_smt_power_savings)
return SD_POWERSAVINGS_BALANCE;

- return 0;
+ return SD_PREFER_SIBLING;
}

/*
diff --git a/kernel/sched.c b/kernel/sched.c
index 584a122..9d64cec 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3811,9 +3811,13 @@ static inline void update_sd_lb_stats(struct sched_domain *sd, int this_cpu,
const struct cpumask *cpus, int *balance,
struct sd_lb_stats *sds)
{
+ struct sched_domain *child = sd->child;
struct sched_group *group = sd->groups;
struct sg_lb_stats sgs;
- int load_idx;
+ int load_idx, prefer_sibling = 0;
+
+ if (child && child->flags & SD_PREFER_SIBLING)
+ prefer_sibling = 1;

init_sd_power_savings_stats(sd, sds, idle);
load_idx = get_sd_load_idx(sd, idle);
@@ -3833,6 +3837,14 @@ static inline void update_sd_lb_stats(struct sched_domain *sd, int this_cpu,
sds->total_load += sgs.group_load;
sds->total_pwr += group->__cpu_power;

+ /*
+ * In case the child domain prefers tasks go to siblings
+ * first, lower the group capacity to one so that we'll try
+ * and move all the excess tasks away.
+ */
+ if (prefer_sibling)
+ sgs.group_capacity = 1;
+
if (local_group) {
sds->this_load = sgs.avg_load;
sds->this = group;

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