Messages in this thread Patch in this message | | | From | Yuyang Du <> | Subject | [RFC PATCH 2/9 v4] sched: Precise accumulated time and acount runnable number in update_entity_runnable_avg | Date | Wed, 25 Jun 2014 08:36:01 +0800 |
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The current amount of time already accumulated against next period is determined by:
delta_w = sa->runnable_avg_period % 1024
Considering the runnable_avg_period is the sum of an infinite series, this method looks gross, even the error would be no more than 1024 (~1ms). But precisely accounting this is not hard, just use a variable period_contrib to record it.
The current runnable argument is either 1 or 0, indicating whether this entity is runnable or not. In order to account the number of runnables as well, change how runnable_avg_sum is accumulated.
Signed-off-by: Yuyang Du <yuyang.du@intel.com> --- include/linux/sched.h | 1 + kernel/sched/fair.c | 12 ++++++++---- 2 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h index 306f4f0..1b1997d 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1074,6 +1074,7 @@ struct sched_avg { * choices of y < 1-2^(-32)*1024. */ u32 runnable_avg_sum, runnable_avg_period; + u32 period_contrib; u64 last_runnable_update; s64 decay_count; unsigned long load_avg_contrib; diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 1a2d04f..e914e32 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2294,10 +2294,12 @@ static __always_inline int __update_entity_runnable_avg(u64 now, sa->last_runnable_update = now; /* delta_w is the amount already accumulated against our next period */ - delta_w = sa->runnable_avg_period % 1024; + delta_w = sa->period_contrib; if (delta + delta_w >= 1024) { /* period roll-over */ decayed = 1; + /* how much left for next period will start over, we don't know yet */ + sa->period_contrib = 0; /* * Now that we know we're crossing a period boundary, figure @@ -2306,7 +2308,7 @@ static __always_inline int __update_entity_runnable_avg(u64 now, */ delta_w = 1024 - delta_w; if (runnable) - sa->runnable_avg_sum += delta_w; + sa->runnable_avg_sum += runnable * delta_w; sa->runnable_avg_period += delta_w; delta -= delta_w; @@ -2323,15 +2325,17 @@ static __always_inline int __update_entity_runnable_avg(u64 now, /* Efficiently calculate \sum (1..n_period) 1024*y^i */ runnable_contrib = __compute_runnable_contrib(periods); if (runnable) - sa->runnable_avg_sum += runnable_contrib; + sa->runnable_avg_sum += runnable * runnable_contrib; sa->runnable_avg_period += runnable_contrib; } /* Remainder of delta accrued against u_0` */ if (runnable) - sa->runnable_avg_sum += delta; + sa->runnable_avg_sum += runnable * delta; sa->runnable_avg_period += delta; + sa->period_contrib += delta; + return decayed; } -- 1.7.9.5
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