delayacct: track delays from IRQ/SOFTIRQ

Delay accounting does not track the delay of IRQ/SOFTIRQ.  While
IRQ/SOFTIRQ could have obvious impact on some workloads productivity, such
as when workloads are running on system which is busy handling network
IRQ/SOFTIRQ.

Get the delay of IRQ/SOFTIRQ could help users to reduce such delay.  Such
as setting interrupt affinity or task affinity, using kernel thread for
NAPI etc.  This is inspired by "sched/psi: Add PSI_IRQ to track
IRQ/SOFTIRQ pressure"[1].  Also fix some code indent problems of older
code.

And update tools/accounting/getdelays.c:
    / # ./getdelays -p 156 -di
    print delayacct stats ON
    printing IO accounting
    PID     156

    CPU             count     real total  virtual total    delay total  delay average
                       15       15836008       16218149      275700790         18.380ms
    IO              count    delay total  delay average
                        0              0          0.000ms
    SWAP            count    delay total  delay average
                        0              0          0.000ms
    RECLAIM         count    delay total  delay average
                        0              0          0.000ms
    THRASHING       count    delay total  delay average
                        0              0          0.000ms
    COMPACT         count    delay total  delay average
                        0              0          0.000ms
    WPCOPY          count    delay total  delay average
                       36        7586118          0.211ms
    IRQ             count    delay total  delay average
                       42         929161          0.022ms

[1] commit 52b1364b("sched/psi: Add PSI_IRQ to track IRQ/SOFTIRQ pressure")

Link: https://lkml.kernel.org/r/202304081728353557233@zte.com.cnSigned-off-by: Yang Yang <yang.yang29@zte.com.cn>
Cc: Jiang Xuexin <jiang.xuexin@zte.com.cn>
Cc: wangyong <wang.yong12@zte.com.cn>
Cc: junhua huang <huang.junhua@zte.com.cn>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Documentation/accounting/delay-accounting.rst

@@ -16,6 +16,7 @@ d) memory reclaim
 e) thrashing
 f) direct compact
 g) write-protect copy
+h) IRQ/SOFTIRQ
 
 and makes these statistics available to userspace through
 the taskstats interface.
@@ -49,7 +50,7 @@ this structure. See
 for a description of the fields pertaining to delay accounting.
 It will generally be in the form of counters returning the cumulative
 delay seen for cpu, sync block I/O, swapin, memory reclaim, thrash page
-cache, direct compact, write-protect copy etc.
+cache, direct compact, write-protect copy, IRQ/SOFTIRQ etc.
 
 Taking the difference of two successive readings of a given
 counter (say cpu_delay_total) for a task will give the delay
@@ -120,6 +121,8 @@ Get sum of delays, since system boot, for all pids with tgid 5::
                        0              0          0.000ms
 	WPCOPY          count    delay total  delay average
                        0              0          0.000ms
+	IRQ             count    delay total  delay average
+                       0              0          0.000ms
 
 Get IO accounting for pid 1, it works only with -p::
 

include/linux/delayacct.h

@@ -48,10 +48,13 @@ struct task_delay_info {
 	u64 wpcopy_start;
 	u64 wpcopy_delay;	/* wait for write-protect copy */
 
+	u64 irq_delay;	/* wait for IRQ/SOFTIRQ */
+
 	u32 freepages_count;	/* total count of memory reclaim */
 	u32 thrashing_count;	/* total count of thrash waits */
 	u32 compact_count;	/* total count of memory compact */
 	u32 wpcopy_count;	/* total count of write-protect copy */
+	u32 irq_count;	/* total count of IRQ/SOFTIRQ */
 };
 #endif
 
@@ -81,6 +84,7 @@ extern void __delayacct_compact_start(void);
 extern void __delayacct_compact_end(void);
 extern void __delayacct_wpcopy_start(void);
 extern void __delayacct_wpcopy_end(void);
+extern void __delayacct_irq(struct task_struct *task, u32 delta);
 
 static inline void delayacct_tsk_init(struct task_struct *tsk)
 {
@@ -215,6 +219,15 @@ static inline void delayacct_wpcopy_end(void)
 		__delayacct_wpcopy_end();
 }
 
+static inline void delayacct_irq(struct task_struct *task, u32 delta)
+{
+	if (!static_branch_unlikely(&delayacct_key))
+		return;
+
+	if (task->delays)
+		__delayacct_irq(task, delta);
+}
+
 #else
 static inline void delayacct_init(void)
 {}
@@ -253,6 +266,8 @@ static inline void delayacct_wpcopy_start(void)
 {}
 static inline void delayacct_wpcopy_end(void)
 {}
+static inline void delayacct_irq(struct task_struct *task, u32 delta)
+{}
 
 #endif /* CONFIG_TASK_DELAY_ACCT */
 

include/uapi/linux/taskstats.h

@@ -34,7 +34,7 @@
  */
 
 
-#define TASKSTATS_VERSION	13
+#define TASKSTATS_VERSION	14
 #define TS_COMM_LEN		32	/* should be >= TASK_COMM_LEN
 					 * in linux/sched.h */
 
@@ -198,6 +198,10 @@ struct taskstats {
 	/* v13: Delay waiting for write-protect copy */
 	__u64    wpcopy_count;
 	__u64    wpcopy_delay_total;
+
+	/* v14: Delay waiting for IRQ/SOFTIRQ */
+	__u64    irq_count;
+	__u64    irq_delay_total;
 };
 
 

kernel/delayacct.c

@@ -179,12 +179,15 @@ int delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
 	d->compact_delay_total = (tmp < d->compact_delay_total) ? 0 : tmp;
 	tmp = d->wpcopy_delay_total + tsk->delays->wpcopy_delay;
 	d->wpcopy_delay_total = (tmp < d->wpcopy_delay_total) ? 0 : tmp;
+	tmp = d->irq_delay_total + tsk->delays->irq_delay;
+	d->irq_delay_total = (tmp < d->irq_delay_total) ? 0 : tmp;
 	d->blkio_count += tsk->delays->blkio_count;
 	d->swapin_count += tsk->delays->swapin_count;
 	d->freepages_count += tsk->delays->freepages_count;
 	d->thrashing_count += tsk->delays->thrashing_count;
 	d->compact_count += tsk->delays->compact_count;
 	d->wpcopy_count += tsk->delays->wpcopy_count;
+	d->irq_count += tsk->delays->irq_count;
 	raw_spin_unlock_irqrestore(&tsk->delays->lock, flags);
 
 	return 0;
@@ -274,3 +277,14 @@ void __delayacct_wpcopy_end(void)
 		      &current->delays->wpcopy_delay,
 		      &current->delays->wpcopy_count);
 }
+
+void __delayacct_irq(struct task_struct *task, u32 delta)
+{
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&task->delays->lock, flags);
+	task->delays->irq_delay += delta;
+	task->delays->irq_count++;
+	raw_spin_unlock_irqrestore(&task->delays->lock, flags);
+}
+

kernel/sched/core.c

@@ -704,6 +704,7 @@ static void update_rq_clock_task(struct rq *rq, s64 delta)
 	rq->prev_irq_time += irq_delta;
 	delta -= irq_delta;
 	psi_account_irqtime(rq->curr, irq_delta);
+	delayacct_irq(rq->curr, irq_delta);
 #endif
 #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
 	if (static_key_false((&paravirt_steal_rq_enabled))) {

tools/accounting/getdelays.c

@@ -208,6 +208,8 @@ static void print_delayacct(struct taskstats *t)
 	       "COMPACT  %12s%15s%15s\n"
 	       "      %15llu%15llu%15.3fms\n"
 	       "WPCOPY   %12s%15s%15s\n"
+	       "      %15llu%15llu%15.3fms\n"
+	       "IRQ   %15s%15s%15s\n"
 	       "      %15llu%15llu%15.3fms\n",
 	       "count", "real total", "virtual total",
 	       "delay total", "delay average",
@@ -239,7 +241,11 @@ static void print_delayacct(struct taskstats *t)
 	       "count", "delay total", "delay average",
 	       (unsigned long long)t->wpcopy_count,
 	       (unsigned long long)t->wpcopy_delay_total,
-          average_ms((double)t->wpcopy_delay_total, t->wpcopy_count));
+	       average_ms((double)t->wpcopy_delay_total, t->wpcopy_count),
+	       "count", "delay total", "delay average",
+	       (unsigned long long)t->irq_count,
+	       (unsigned long long)t->irq_delay_total,
+	       average_ms((double)t->irq_delay_total, t->irq_count));
 }
 
 static void task_context_switch_counts(struct taskstats *t)