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sched: walt: Introduce bucket bitmask

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In get_pred_busy, we attempt to find the closing bucket, which is
nothing but the first bucket which is filled after the start bucket.

We can optimize this computation by using a bitmask of buckets.

Change-Id: I377be499fdd4876d5d3a43e8ebb34a489e6ae17b
Signed-off-by: Shaleen Agrawal <quic_shalagra@quicinc.com>
This commit is contained in:
Shaleen Agrawal 2022-02-09 11:30:06 -08:00 committed by Rishabh Bhatnagar
parent ef3ba55b55
commit a8e14cc963
2 changed files with 16 additions and 16 deletions
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1
include/linux/sched/walt.h
View File

@ -92,6 +92,7 @@ struct walt_task_struct {
u32 curr_window, prev_window;
u32 pred_demand;
u8 busy_buckets[NUM_BUSY_BUCKETS];
u16 bucket_bitmask;
u16 demand_scaled;
u16 pred_demand_scaled;
u64 active_time;

31
kernel/sched/walt/walt.c
View File

@ -1135,7 +1135,7 @@ static void set_window_start(struct rq *rq)
* decayed. The rate of increase and decay could be different based
* on current count in the bucket.
*/
static inline void bucket_increase(u8 *buckets, int idx)
static inline void bucket_increase(u8 *buckets, u16 *bucket_bitmask, int idx)
{
int i, step;
@ -1143,8 +1143,10 @@ static inline void bucket_increase(u8 *buckets, int idx)
if (idx != i) {
if (buckets[i] > DEC_STEP)
buckets[i] -= DEC_STEP;
else
else {
buckets[i] = 0;
*bucket_bitmask &= ~BIT_MASK(i);
}
} else {
step = buckets[i] >= CONSISTENT_THRES ?
INC_STEP_BIG : INC_STEP;
@ -1152,6 +1154,7 @@ static inline void bucket_increase(u8 *buckets, int idx)
buckets[i] = U8_MAX;
else
buckets[i] += step;
*bucket_bitmask |= BIT_MASK(i);
}
}
}
@ -1191,27 +1194,23 @@ static inline int busy_to_bucket(u32 normalized_rt)
* to use for prediction. Once found, it returns the midpoint of that bucket.
*/
static u32 get_pred_busy(struct task_struct *p,
int start, u32 runtime)
int start, u32 runtime, u16 bucket_bitmask)
{
int i;
struct walt_task_struct *wts = (struct walt_task_struct *) p->android_vendor_data1;
u8 *buckets = wts->busy_buckets;
u32 dmin, dmax;
u64 cur_freq_runtime = 0;
int first = NUM_BUSY_BUCKETS, final;
int first = NUM_BUSY_BUCKETS, final = NUM_BUSY_BUCKETS;
u32 ret = runtime;
u16 next_mask = bucket_bitmask >> start;
/* skip prediction for new tasks due to lack of history */
if (unlikely(is_new_task(p)))
goto out;
/* find minimal bucket index to pick */
for (i = start; i < NUM_BUSY_BUCKETS; i++) {
if (buckets[i]) {
first = i;
break;
}
}
if (next_mask)
first = ffs(next_mask) - 1 + start;
/* if no higher buckets are filled, predict runtime */
if (first >= NUM_BUSY_BUCKETS)
goto out;
@ -1249,7 +1248,7 @@ static inline u32 calc_pred_demand(struct task_struct *p)
return wts->pred_demand;
return get_pred_busy(p, busy_to_bucket(wts->curr_window),
wts->curr_window);
wts->curr_window, wts->bucket_bitmask);
}
/*
@ -1809,8 +1808,8 @@ static inline u32 predict_and_update_buckets(
struct walt_task_struct *wts = (struct walt_task_struct *) p->android_vendor_data1;
bidx = busy_to_bucket(runtime);
pred_demand = get_pred_busy(p, bidx, runtime);
bucket_increase(wts->busy_buckets, bidx);
pred_demand = get_pred_busy(p, bidx, runtime, wts->bucket_bitmask);
bucket_increase(wts->busy_buckets, &wts->bucket_bitmask, bidx);
return pred_demand;
}
@ -2237,7 +2236,7 @@ static void init_new_task_load(struct task_struct *p)
for (i = 0; i < NUM_BUSY_BUCKETS; ++i)
wts->busy_buckets[i] = 0;
wts->bucket_bitmask = 0;
wts->cpu_cycles = 0;
memset(wts->curr_window_cpu, 0, sizeof(u32) * WALT_NR_CPUS);