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Subject[PATCH v1 18/19] sched: update shares distribution to use u64
Date
Update the shares distribution code to use u64. We still maintain tg->shares as
an unsigned long since sched entity weights can't exceed MAX_SHARES (2^28). This
patch updates all the calculations required to estimate shares to use u64.

Signed-off-by: Nikhil Rao <ncrao@google.com>
---
kernel/sched.c | 2 +-
kernel/sched_debug.c | 6 +++---
kernel/sched_fair.c | 17 ++++++++++++-----
3 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index 6b9b02a..e131225 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -367,7 +367,7 @@ struct cfs_rq {
u64 load_period;
u64 load_stamp, load_last, load_unacc_exec_time;

- unsigned long load_contribution;
+ u64 load_contribution;
#endif
#endif
};
diff --git a/kernel/sched_debug.c b/kernel/sched_debug.c
index d22b666..b809651 100644
--- a/kernel/sched_debug.c
+++ b/kernel/sched_debug.c
@@ -204,11 +204,11 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq)
SEQ_printf(m, " .%-30s: %lld\n", "load", cfs_rq->load.weight);
#ifdef CONFIG_FAIR_GROUP_SCHED
#ifdef CONFIG_SMP
- SEQ_printf(m, " .%-30s: %Ld.%06ld\n", "load_avg",
+ SEQ_printf(m, " .%-30s: %lld.%06ld\n", "load_avg",
SPLIT_NS(cfs_rq->load_avg));
- SEQ_printf(m, " .%-30s: %Ld.%06ld\n", "load_period",
+ SEQ_printf(m, " .%-30s: %lld.%06ld\n", "load_period",
SPLIT_NS(cfs_rq->load_period));
- SEQ_printf(m, " .%-30s: %ld\n", "load_contrib",
+ SEQ_printf(m, " .%-30s: %lld\n", "load_contrib",
cfs_rq->load_contribution);
SEQ_printf(m, " .%-30s: %d\n", "load_tg",
atomic_read(&cfs_rq->tg->load_weight));
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index bf9bbaa..3f56410 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -708,12 +708,13 @@ static void update_cfs_rq_load_contribution(struct cfs_rq *cfs_rq,
int global_update)
{
struct task_group *tg = cfs_rq->tg;
- long load_avg;
+ s64 load_avg;

load_avg = div64_u64(cfs_rq->load_avg, cfs_rq->load_period+1);
load_avg -= cfs_rq->load_contribution;

if (global_update || abs(load_avg) > cfs_rq->load_contribution / 8) {
+ /* TODO: fix atomics for 64-bit additions */
atomic_add(load_avg, &tg->load_weight);
cfs_rq->load_contribution += load_avg;
}
@@ -723,7 +724,7 @@ static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
{
u64 period = sysctl_sched_shares_window;
u64 now, delta;
- unsigned long load = cfs_rq->load.weight;
+ u64 load = cfs_rq->load.weight;

if (cfs_rq->tg == &root_task_group)
return;
@@ -743,8 +744,13 @@ static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
cfs_rq->load_unacc_exec_time = 0;
cfs_rq->load_period += delta;
if (load) {
+ u64 tmp = cfs_rq->load_avg;
cfs_rq->load_last = now;
cfs_rq->load_avg += delta * load;
+
+ /* Detect overflow and set load_avg to max */
+ if (unlikely(cfs_rq->load_avg < tmp))
+ cfs_rq->load_avg = ~0ULL;
}

/* consider updating load contribution on each fold or truncate */
@@ -769,24 +775,25 @@ static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)

static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
{
- long load_weight, load, shares;
+ s64 load_weight, load, shares;

load = cfs_rq->load.weight;

+ /* TODO: fixup atomics to handle u64 in 32-bit */
load_weight = atomic_read(&tg->load_weight);
load_weight += load;
load_weight -= cfs_rq->load_contribution;

shares = (tg->shares * load);
if (load_weight)
- shares /= load_weight;
+ shares = div64_u64(shares, load_weight);

if (shares < MIN_SHARES)
shares = MIN_SHARES;
if (shares > tg->shares)
shares = tg->shares;

- return shares;
+ return (long)shares;
}

static void update_entity_shares_tick(struct cfs_rq *cfs_rq)
--
1.7.3.1


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