diff options
| author | Yuyang Du <yuyang.du@intel.com> | 2016-04-05 12:12:26 +0800 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-05-05 09:24:00 +0200 |
| commit | 6ecdd74962f246dfe8750b7bea481a1c0816315d (patch) | |
| tree | 3b07aefd3f08af08e983771f34eb1f9037cc7848 /kernel/sched/sched.h | |
| parent | 2159197d66770ec01f75c93fb11dc66df81fd45b (diff) | |
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 'kernel/sched/sched.h')
| -rw-r--r-- | kernel/sched/sched.h | 15 |
1 files changed, 10 insertions, 5 deletions
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 066a4c2d2695..ad83361f9e67 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -56,18 +56,23 @@ static inline void cpu_load_update_active(struct rq *this_rq) { } * increase coverage and consistency always enable it on 64bit platforms. */ #ifdef CONFIG_64BIT -# define SCHED_LOAD_RESOLUTION 10 -# define scale_load(w) ((w) << SCHED_LOAD_RESOLUTION) -# define scale_load_down(w) ((w) >> SCHED_LOAD_RESOLUTION) +# define SCHED_LOAD_SHIFT (SCHED_FIXEDPOINT_SHIFT + SCHED_FIXEDPOINT_SHIFT) +# define scale_load(w) ((w) << SCHED_FIXEDPOINT_SHIFT) +# define scale_load_down(w) ((w) >> SCHED_FIXEDPOINT_SHIFT) #else -# define SCHED_LOAD_RESOLUTION 0 +# define SCHED_LOAD_SHIFT (SCHED_FIXEDPOINT_SHIFT) # define scale_load(w) (w) # define scale_load_down(w) (w) #endif -#define SCHED_LOAD_SHIFT (10 + SCHED_LOAD_RESOLUTION) #define SCHED_LOAD_SCALE (1L << SCHED_LOAD_SHIFT) +/* + * NICE_0's weight (visible to users) and its load (invisible to users) have + * independent ranges, but they should be well calibrated. We use scale_load() + * and scale_load_down(w) to convert between them, and the following must be true: + * scale_load(sched_prio_to_weight[20]) == NICE_0_LOAD + */ #define NICE_0_LOAD SCHED_LOAD_SCALE #define NICE_0_SHIFT SCHED_LOAD_SHIFT |