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Subject[RFC][PATCH 2/8] sched: SD_PREFER_SIBLING
Do the placement thing using SD flags

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
include/linux/sched.h | 29 +++++++++++++++--------------
kernel/sched.c | 14 +++++++++++++-
2 files changed, 28 insertions(+), 15 deletions(-)
Index: linux-2.6/include/linux/sched.h
===================================================================
--- linux-2.6.orig/include/linux/sched.h
+++ linux-2.6/include/linux/sched.h
@@ -808,18 +808,19 @@ 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 */
@@ -839,7 +840,7 @@ static inline int sd_balance_for_mc_powe
if (sched_smt_power_savings)
return SD_POWERSAVINGS_BALANCE;

- return 0;
+ return SD_PREFER_SIBLING;
}

static inline int sd_balance_for_package_power(void)
@@ -847,7 +848,7 @@ static inline int sd_balance_for_package
if (sched_mc_power_savings | sched_smt_power_savings)
return SD_POWERSAVINGS_BALANCE;

- return 0;
+ return SD_PREFER_SIBLING;
}

/*
Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -3803,9 +3803,13 @@ static inline void update_sd_lb_stats(st
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);
@@ -3825,6 +3829,14 @@ static inline void update_sd_lb_stats(st
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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