diff options
author | Yuyang Du <yuyang.du@intel.com> | 2016-04-05 07:12:26 +0300 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2016-05-05 10:24:00 +0300 |
commit | 6ecdd74962f246dfe8750b7bea481a1c0816315d (patch) | |
tree | 3b07aefd3f08af08e983771f34eb1f9037cc7848 /include/linux/sched.h | |
parent | 2159197d66770ec01f75c93fb11dc66df81fd45b (diff) | |
download | linux-6ecdd74962f246dfe8750b7bea481a1c0816315d.tar.xz |
sched/fair: Generalize the load/util averages resolution definition
Integer metric needs fixed point arithmetic. In sched/fair, a few
metrics, e.g., weight, load, load_avg, util_avg, freq, and capacity,
may have different fixed point ranges, which makes their update and
usage error-prone.
In order to avoid the errors relating to the fixed point range, we
definie a basic fixed point range, and then formalize all metrics to
base on the basic range.
The basic range is 1024 or (1 << 10). Further, one can recursively
apply the basic range to have larger range.
Pointed out by Ben Segall, weight (visible to user, e.g., NICE-0 has
1024) and load (e.g., NICE_0_LOAD) have independent ranges, but they
must be well calibrated.
Signed-off-by: Yuyang Du <yuyang.du@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bsegall@google.com
Cc: dietmar.eggemann@arm.com
Cc: lizefan@huawei.com
Cc: morten.rasmussen@arm.com
Cc: pjt@google.com
Cc: umgwanakikbuti@gmail.com
Cc: vincent.guittot@linaro.org
Link: http://lkml.kernel.org/r/1459829551-21625-2-git-send-email-yuyang.du@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/linux/sched.h')
-rw-r--r-- | include/linux/sched.h | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h index d894f2d61388..7d779d70a3a5 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -937,9 +937,19 @@ enum cpu_idle_type { }; /* + * Integer metrics need fixed point arithmetic, e.g., sched/fair + * has a few: load, load_avg, util_avg, freq, and capacity. + * + * We define a basic fixed point arithmetic range, and then formalize + * all these metrics based on that basic range. + */ +# define SCHED_FIXEDPOINT_SHIFT 10 +# define SCHED_FIXEDPOINT_SCALE (1L << SCHED_FIXEDPOINT_SHIFT) + +/* * Increase resolution of cpu_capacity calculations */ -#define SCHED_CAPACITY_SHIFT 10 +#define SCHED_CAPACITY_SHIFT SCHED_FIXEDPOINT_SHIFT #define SCHED_CAPACITY_SCALE (1L << SCHED_CAPACITY_SHIFT) /* @@ -1205,8 +1215,8 @@ struct load_weight { * 1) load_avg factors frequency scaling into the amount of time that a * sched_entity is runnable on a rq into its weight. For cfs_rq, it is the * aggregated such weights of all runnable and blocked sched_entities. - * 2) util_avg factors frequency and cpu scaling into the amount of time - * that a sched_entity is running on a CPU, in the range [0..SCHED_LOAD_SCALE]. + * 2) util_avg factors frequency and cpu capacity scaling into the amount of time + * that a sched_entity is running on a CPU, in the range [0..SCHED_CAPACITY_SCALE]. * For cfs_rq, it is the aggregated such times of all runnable and * blocked sched_entities. * The 64 bit load_sum can: |