Re: [Xenomai-core] [RFC, PATCH] per-thread exec-time stats

[Jan Kiszka <jan.kiszka@domain.hid>]

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Jan Kiszka wrote:

> Here is such a patch + a reworked version of the exec-time stats. Compiles and boots,
> doesn't cause obvious troubles when running in a loop while threads are created and
> destroyed in parallel. Nevertheless, a quick hack which may contain bugs.

As expected, there were bugs. This version of the exec-time patch always uses TSC for
timestamping and the related correct conversion function. And it doesn't try to update
the exec-time across CPUs as the TSCs may not be in sync. Thus, when there is no
scheduling activity on some CPU, we may not see progress in /stat. But this is the least
invasive way, and we typically DO have activity anyway.

Jan


---
 include/nucleus/pod.h    |   28 ++++++++++++++++++++++++++++
 include/nucleus/thread.h |    1 +
 ksrc/nucleus/module.c    |   20 ++++++++++++++++----
 ksrc/nucleus/pod.c       |    5 +++++
 ksrc/nucleus/thread.c    |    1 +
 5 files changed, 51 insertions(+), 4 deletions(-)

Index: include/nucleus/thread.h
===================================================================
--- include/nucleus/thread.h.orig
+++ include/nucleus/thread.h
@@ -152,6 +152,7 @@ typedef struct xnthread {
 	unsigned long csw;	/* Context switches (includes
 				   secondary -> primary switches) */
 	unsigned long pf;	/* Number of page faults */
+	xnticks_t exec_time;	/* Accumulated execution time (ticks) */
     } stat;
 #endif /* CONFIG_XENO_OPT_STATS */
 
Index: include/nucleus/pod.h
===================================================================
--- include/nucleus/pod.h.orig
+++ include/nucleus/pod.h
@@ -145,6 +145,10 @@ typedef struct xnsched {
 
     xnthread_t rootcb;          /*!< Root thread control block. */
 
+#ifdef CONFIG_XENO_OPT_STATS
+    xnticks_t last_csw;         /*!< Last context switch (ticks). */
+#endif /* CONFIG_XENO_OPT_STATS */
+
 } xnsched_t;
 
 #ifdef CONFIG_SMP
@@ -545,6 +549,30 @@ static inline void xnpod_delete_self (vo
     xnpod_delete_thread(xnpod_current_thread());
 }
 
+#ifdef CONFIG_XENO_OPT_STATS
+static inline void xnpod_acc_exec_time(xnthread_t *thread)
+{
+    xnsched_t *sched = thread->sched;
+    xnticks_t now = xnarch_get_cpu_tsc();
+
+    thread->stat.exec_time += now - sched->last_csw;
+    sched->last_csw = now;
+}
+
+static inline void xnpod_update_csw_date(xnsched_t *sched)
+{
+    sched->last_csw = xnarch_get_cpu_tsc();
+}
+#else /* !CONFIG_XENO_OPT_STATS */
+static inline void xnpod_acc_exec_time(xnthread_t *thread)
+{
+}
+
+static inline void xnpod_update_csw_date(xnsched_t *sched)
+{
+}
+#endif /* CONFIG_XENO_OPT_STATS */
+
 #ifdef __cplusplus
 }
 #endif
Index: ksrc/nucleus/thread.c
===================================================================
--- ksrc/nucleus/thread.c.orig
+++ ksrc/nucleus/thread.c
@@ -90,6 +90,7 @@ int xnthread_init(xnthread_t *thread,
 	thread->stat.ssw = 0;
 	thread->stat.csw = 0;
 	thread->stat.pf = 0;
+	thread->stat.exec_time = 0;
 #endif /* CONFIG_XENO_OPT_STATS */
 
 	/* These will be filled by xnpod_start_thread() */
Index: ksrc/nucleus/pod.c
===================================================================
--- ksrc/nucleus/pod.c.orig
+++ ksrc/nucleus/pod.c
@@ -669,6 +669,9 @@ static inline void xnpod_switch_zombie(x
 
 	xnthread_cleanup_tcb(threadout);
 
+	/* no need to update stats of dying thread */
+	xnpod_update_csw_date(sched);
+
 	xnarch_finalize_and_switch(xnthread_archtcb(threadout),
 				   xnthread_archtcb(threadin));
 
@@ -2433,6 +2436,7 @@ void xnpod_schedule(void)
 		xnarch_enter_root(xnthread_archtcb(threadin));
 	}
 
+	xnpod_acc_exec_time(threadout);
 	xnthread_inc_csw(threadin);
 
 	xnarch_switch_to(xnthread_archtcb(threadout),
@@ -2604,6 +2608,7 @@ void xnpod_schedule_runnable(xnthread_t 
 		nkpod->schedhook(runthread, XNREADY);
 #endif /* __XENO_SIM__ */
 
+	xnpod_acc_exec_time(runthread);
 	xnthread_inc_csw(threadin);
 
 	xnarch_switch_to(xnthread_archtcb(runthread),
Index: ksrc/nucleus/module.c
===================================================================
--- ksrc/nucleus/module.c.orig
+++ ksrc/nucleus/module.c
@@ -269,6 +269,7 @@ struct stat_seq_iterator {
 		unsigned long ssw;
 		unsigned long csw;
 		unsigned long pf;
+		xnticks_t exec_time;
 	} stat_info[1];
 };
 
@@ -309,13 +310,17 @@ static void stat_seq_stop(struct seq_fil
 static int stat_seq_show(struct seq_file *seq, void *v)
 {
 	if (v == SEQ_START_TOKEN)
-		seq_printf(seq, "%-3s  %-6s %-10s %-10s %-4s  %-8s  %s\n",
-			   "CPU", "PID", "MSW", "CSW", "PF", "STAT", "NAME");
+		seq_printf(seq, "%-3s  %-6s %-10s %-10s %-4s  %-8s  %12s"
+			   "  %s\n",
+			   "CPU", "PID", "MSW", "CSW", "PF", "STAT", "TIME",
+			   "NAME");
 	else {
 		struct stat_seq_info *p = (struct stat_seq_info *)v;
-		seq_printf(seq, "%3u  %-6d %-10lu %-10lu %-4lu  %.8lx  %s\n",
+		unsigned long long exec_time = xnarch_tsc_to_ns(p->exec_time);
+		seq_printf(seq, "%3u  %-6d %-10lu %-10lu %-4lu  %.8lx  %12llu"
+			   "  %s\n",
 			   p->cpu, p->pid, p->ssw, p->csw, p->pf, p->status,
-			   p->name);
+			   xnarch_ulldiv(exec_time, 1000, NULL), p->name);
 	}
 
 	return 0;
@@ -365,6 +370,12 @@ static int stat_seq_open(struct inode *i
 
 	iter->nentries = 0;
 
+	/* Update exec-time stats at least on current CPU, unsync'ed TSCs
+	   prevent cross-CPU update yet. */
+	xnlock_get_irqsave(&nklock, s);
+	xnpod_acc_exec_time(xnpod_current_thread());
+	xnlock_put_irqrestore(&nklock, s);
+
 	/* Take a snapshot element-wise, restart if something changes
 	   underneath us. */
 
@@ -389,6 +400,7 @@ static int stat_seq_open(struct inode *i
 		iter->stat_info[n].ssw = thread->stat.ssw;
 		iter->stat_info[n].csw = thread->stat.csw;
 		iter->stat_info[n].pf = thread->stat.pf;
+		iter->stat_info[n].exec_time = thread->stat.exec_time;
 
 		holder = nextq(&nkpod->threadq, holder);
 




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