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authorIngo Molnar <mingo@elte.hu>2006-02-17 13:52:44 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-02-17 13:59:26 -0800
commit4bbf39c29bc3409d6454faf0dfa1b3b0aa2ac2af (patch)
tree2f8ed8aa42a1645a9cb3306ce93c9e4b63536630
parent05efc67d100ff6c3364604b72729addf1a86fdab (diff)
downloadop-kernel-dev-4bbf39c29bc3409d6454faf0dfa1b3b0aa2ac2af.zip
op-kernel-dev-4bbf39c29bc3409d6454faf0dfa1b3b0aa2ac2af.tar.gz
[PATCH] Introduce CONFIG_DEFAULT_MIGRATION_COST
Heiko Carstens <heiko.carstens@de.ibm.com> wrote: The boot sequence on s390 sometimes takes ages and we spend a very long time (up to one or two minutes) in calibrate_migration_costs. The time spent there differs from boot to boot. Also the calculated costs differ a lot. I've seen differences by up to a factor of 15 (yes, factor not percent). Also I doubt that making these measurements make much sense on a completely virtualized architecture where you cannot tell how much cpu time you will get anyway. So introduce the CONFIG_DEFAULT_MIGRATION_COST method for an architecture to set the scheduler migration costs. This turns off automatic detection of migration costs. Makes sense on virtual platforms, where migration costs are hard to measure accurately. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--arch/s390/Kconfig4
-rw-r--r--kernel/sched.c13
2 files changed, 16 insertions, 1 deletions
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index b66602a..b7ca5bf 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -80,6 +80,10 @@ config HOTPLUG_CPU
can be controlled through /sys/devices/system/cpu/cpu#.
Say N if you want to disable CPU hotplug.
+config DEFAULT_MIGRATION_COST
+ int
+ default "1000000"
+
config MATHEMU
bool "IEEE FPU emulation"
depends on MARCH_G5
diff --git a/kernel/sched.c b/kernel/sched.c
index 66d9572..12d291b 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5058,7 +5058,18 @@ static void init_sched_build_groups(struct sched_group groups[], cpumask_t span,
#define MAX_DOMAIN_DISTANCE 32
static unsigned long long migration_cost[MAX_DOMAIN_DISTANCE] =
- { [ 0 ... MAX_DOMAIN_DISTANCE-1 ] = -1LL };
+ { [ 0 ... MAX_DOMAIN_DISTANCE-1 ] =
+/*
+ * Architectures may override the migration cost and thus avoid
+ * boot-time calibration. Unit is nanoseconds. Mostly useful for
+ * virtualized hardware:
+ */
+#ifdef CONFIG_DEFAULT_MIGRATION_COST
+ CONFIG_DEFAULT_MIGRATION_COST
+#else
+ -1LL
+#endif
+};
/*
* Allow override of migration cost - in units of microseconds.
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