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Subject[PATCH 5/6] Account ksoftirq time as cpustat softirq
Date
softirq time in ksoftirqd context is not accounted in ns granularity
per cpu softirq stats, as we want that to be a part of ksoftirqd
exec_runtime.

Accounting them separately, and using them while doing stats makes
/proc/stat include that time in cpu si time.

Signed-off-by: Venkatesh Pallipadi <venki@google.com>
---
kernel/sched.c | 28 +++++++++++++++++++++-------
1 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index 7e812a6..cba8090 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1941,6 +1941,7 @@ static void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
*/
static DEFINE_PER_CPU(u64, cpu_hardirq_time);
static DEFINE_PER_CPU(u64, cpu_softirq_time);
+static DEFINE_PER_CPU(u64, cpu_ksoftirqd_time);

static DEFINE_PER_CPU(u64, irq_start_time);
static int sched_clock_irqtime;
@@ -1979,15 +1980,20 @@ void account_system_vtime(struct task_struct *curr)
delta = now - per_cpu(irq_start_time, cpu);
per_cpu(irq_start_time, cpu) = now;
/*
- * We do not account for softirq time from ksoftirqd here.
* We want to continue accounting softirq time to ksoftirqd thread
* in that case, so as not to confuse scheduler with a special task
* that do not consume any time, but still wants to run.
+ * So, softirq time in ksoftirqd is accounted separately and used
+ * for softirq time reporting in /proc/stat.
*/
- if (in_irq())
+ if (in_irq()) {
per_cpu(cpu_hardirq_time, cpu) += delta;
- else if (in_serving_softirq() && !(is_ksoftirqd_context()))
- per_cpu(cpu_softirq_time, cpu) += delta;
+ } else if (in_serving_softirq()) {
+ if (is_ksoftirqd_context())
+ per_cpu(cpu_ksoftirqd_time, cpu) += delta;
+ else
+ per_cpu(cpu_softirq_time, cpu) += delta;
+ }

local_irq_restore(flags);
}
@@ -2025,7 +2031,9 @@ static int irqtime_account_si_update(void)
int ret = 0;

local_irq_save(flags);
- latest_ns = __get_cpu_var(cpu_softirq_time);
+ latest_ns = __get_cpu_var(cpu_softirq_time) +
+ __get_cpu_var(cpu_ksoftirqd_time);
+
if (cputime64_gt(nsecs_to_cputime64(latest_ns), cpustat->softirq))
ret = 1;
local_irq_restore(flags);
@@ -3606,7 +3614,8 @@ void account_system_time(struct task_struct *p, int hardirq_offset,
* no timer going off while we are on hardirq and hence we may never get an
* oppurtunity to update it solely in system time.
* p->stime and friends are only updated on system time and not on irq
- * softirq as those do not count in task exec_runtime any more.
+ * softirq as those do not count in task exec_runtime any more (except
+ * for ksoftirqd).
*/
static void irqtime_account_process_tick(struct task_struct *p, int user_tick,
struct rq *rq)
@@ -3620,7 +3629,12 @@ static void irqtime_account_process_tick(struct task_struct *p, int user_tick,
} else if (user_tick) {
account_user_time(p, cputime_one_jiffy, one_jiffy_scaled);
} else if (irqtime_account_si_update()) {
- cpustat->softirq = cputime64_add(cpustat->softirq, tmp);
+ if (is_ksoftirqd_context()) {
+ __account_system_time(p, cputime_one_jiffy,
+ one_jiffy_scaled, &cpustat->softirq);
+ } else {
+ cpustat->softirq = cputime64_add(cpustat->softirq, tmp);
+ }
} else if (p == rq->idle) {
account_idle_time(cputime_one_jiffy);
} else if (p->flags & PF_VCPU) { /* System time or guest time */
--
1.7.1


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