kernel/sched/stats.c | 86 ++++++++++++++++++++++++++------------------ 1 file changed, 52 insertions(+), 34 deletions(-)
Function seq_printf supports rich format string for decimals printing,
but there is no need for it in /proc/schedstat, since majority of the
data is space separared decimals. Use seq_put_decimal_ull instead as
faster alternative.
Performance counter stats (truncated) for sh -c 'cat /proc/schedstat >
/dev/null' before and after applying the patch from machine with 72 CPUs
are below.
Before:
2.94 msec task-clock # 0.820 CPUs utilized
1 context-switches # 340.551 /sec
0 cpu-migrations # 0.000 /sec
340 page-faults # 115.787 K/sec
10,327,200 instructions # 1.89 insn per cycle
# 0.10 stalled cycles per insn
5,458,307 cycles # 1.859 GHz
1,052,733 stalled-cycles-frontend # 19.29% frontend cycles idle
2,066,321 branches # 703.687 M/sec
25,621 branch-misses # 1.24% of all branches
0.00357974 +- 0.00000209 seconds time elapsed ( +- 0.06% )
After:
2.50 msec task-clock # 0.785 CPUs utilized
1 context-switches # 399.780 /sec
0 cpu-migrations # 0.000 /sec
340 page-faults # 135.925 K/sec
7,371,867 instructions # 1.59 insn per cycle
# 0.13 stalled cycles per insn
4,647,053 cycles # 1.858 GHz
986,487 stalled-cycles-frontend # 21.23% frontend cycles idle
1,591,374 branches # 636.199 M/sec
28,973 branch-misses # 1.82% of all branches
0.00318461 +- 0.00000295 seconds time elapsed ( +- 0.09% )
This is ~11% (relative) improvement in time elapsed.
Signed-off-by: Dmitry Ilvokhin <d@ilvokhin.com>
---
kernel/sched/stats.c | 86 ++++++++++++++++++++++++++------------------
1 file changed, 52 insertions(+), 34 deletions(-)
diff --git a/kernel/sched/stats.c b/kernel/sched/stats.c
index d1c9429a4ac5..b304f821e8ff 100644
--- a/kernel/sched/stats.c
+++ b/kernel/sched/stats.c
@@ -98,6 +98,56 @@ void __update_stats_enqueue_sleeper(struct rq *rq, struct task_struct *p,
}
}
+static void show_runqueue_stats(struct seq_file *seq, int cpu, struct rq *rq)
+{
+ seq_printf(seq, "cpu%d", cpu);
+ seq_put_decimal_ull(seq, " ", rq->yld_count);
+ seq_put_decimal_ull(seq, " ", 0);
+ seq_put_decimal_ull(seq, " ", rq->sched_count);
+ seq_put_decimal_ull(seq, " ", rq->sched_goidle);
+ seq_put_decimal_ull(seq, " ", rq->ttwu_count);
+ seq_put_decimal_ull(seq, " ", rq->ttwu_local);
+ seq_put_decimal_ull(seq, " ", rq->rq_cpu_time);
+ seq_put_decimal_ull(seq, " ", rq->rq_sched_info.run_delay);
+ seq_put_decimal_ull(seq, " ", rq->rq_sched_info.pcount);
+ seq_putc(seq, '\n');
+}
+
+static void show_domain_stats(struct seq_file *seq, int dcount,
+ struct sched_domain *sd)
+{
+ enum cpu_idle_type itype;
+
+ seq_printf(seq, "domain%d %s %*pb", dcount, sd->name,
+ cpumask_pr_args(sched_domain_span(sd)));
+ for (itype = 0; itype < CPU_MAX_IDLE_TYPES; itype++) {
+ seq_put_decimal_ull(seq, " ", sd->lb_count[itype]);
+ seq_put_decimal_ull(seq, " ", sd->lb_balanced[itype]);
+ seq_put_decimal_ull(seq, " ", sd->lb_failed[itype]);
+ seq_put_decimal_ull(seq, " ", sd->lb_imbalance_load[itype]);
+ seq_put_decimal_ull(seq, " ", sd->lb_imbalance_util[itype]);
+ seq_put_decimal_ull(seq, " ", sd->lb_imbalance_task[itype]);
+ seq_put_decimal_ull(seq, " ", sd->lb_imbalance_misfit[itype]);
+ seq_put_decimal_ull(seq, " ", sd->lb_gained[itype]);
+ seq_put_decimal_ull(seq, " ", sd->lb_hot_gained[itype]);
+ seq_put_decimal_ull(seq, " ", sd->lb_nobusyq[itype]);
+ seq_put_decimal_ull(seq, " ", sd->lb_nobusyg[itype]);
+ }
+ seq_put_decimal_ull(seq, " ", sd->alb_count);
+ seq_put_decimal_ull(seq, " ", sd->alb_failed);
+ seq_put_decimal_ull(seq, " ", sd->alb_pushed);
+ seq_put_decimal_ull(seq, " ", sd->sbe_count);
+ seq_put_decimal_ull(seq, " ", sd->sbe_balanced);
+ seq_put_decimal_ull(seq, " ", sd->sbe_pushed);
+ seq_put_decimal_ull(seq, " ", sd->sbf_count);
+ seq_put_decimal_ull(seq, " ", sd->sbf_balanced);
+ seq_put_decimal_ull(seq, " ", sd->sbf_pushed);
+ seq_put_decimal_ull(seq, " ", sd->ttwu_wake_remote);
+ seq_put_decimal_ull(seq, " ", sd->ttwu_move_affine);
+ seq_put_decimal_ull(seq, " ", sd->ttwu_move_balance);
+ seq_putc(seq, '\n');
+}
+
/*
* Current schedstat API version.
*
@@ -121,44 +171,12 @@ static int show_schedstat(struct seq_file *seq, void *v)
rq = cpu_rq(cpu);
/* runqueue-specific stats */
- seq_printf(seq,
- "cpu%d %u 0 %u %u %u %u %llu %llu %lu",
- cpu, rq->yld_count,
- rq->sched_count, rq->sched_goidle,
- rq->ttwu_count, rq->ttwu_local,
- rq->rq_cpu_time,
- rq->rq_sched_info.run_delay, rq->rq_sched_info.pcount);
-
- seq_printf(seq, "\n");
+ show_runqueue_stats(seq, cpu, rq);
/* domain-specific stats */
rcu_read_lock();
for_each_domain(cpu, sd) {
- enum cpu_idle_type itype;
-
- seq_printf(seq, "domain%d %s %*pb", dcount++, sd->name,
- cpumask_pr_args(sched_domain_span(sd)));
- for (itype = 0; itype < CPU_MAX_IDLE_TYPES; itype++) {
- seq_printf(seq, " %u %u %u %u %u %u %u %u %u %u %u",
- sd->lb_count[itype],
- sd->lb_balanced[itype],
- sd->lb_failed[itype],
- sd->lb_imbalance_load[itype],
- sd->lb_imbalance_util[itype],
- sd->lb_imbalance_task[itype],
- sd->lb_imbalance_misfit[itype],
- sd->lb_gained[itype],
- sd->lb_hot_gained[itype],
- sd->lb_nobusyq[itype],
- sd->lb_nobusyg[itype]);
- }
- seq_printf(seq,
- " %u %u %u %u %u %u %u %u %u %u %u %u\n",
- sd->alb_count, sd->alb_failed, sd->alb_pushed,
- sd->sbe_count, sd->sbe_balanced, sd->sbe_pushed,
- sd->sbf_count, sd->sbf_balanced, sd->sbf_pushed,
- sd->ttwu_wake_remote, sd->ttwu_move_affine,
- sd->ttwu_move_balance);
+ show_domain_stats(seq, dcount++, sd);
}
rcu_read_unlock();
}
--
2.47.3Hello everyone, I wanted to follow up on this patch and see if the proposed changes look reasonable to you. I'd greatly appreciate any feedback you may have, and thank you in advance for taking the time to review it. Best regards, Dmitry
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