linux-kernel - [PATCH 3/5] mmiotrace: print overrun counts

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Message-ID: <20080427223708.2137ba95@daedalus.pq.iki.fi>
Date:	Sun, 27 Apr 2008 22:37:08 +0300
From:	Pekka Paalanen <pq@....fi>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Pekka Paalanen <pq@....fi>, Steven Rostedt <rostedt@...dmis.org>,
	linux-kernel@...r.kernel.org, akpm@...l.org,
	Peter Zijlstra <peterz@...radead.org>,
	Soeren Sandmann Pedersen <sandmann@...hat.com>,
	Steven Rostedt <srostedt@...hat.com>,
	Pavel Roskin <proski@....org>
Subject: [PATCH 3/5] mmiotrace: print overrun counts

>From d5c3a38d48e223bcf192f48a8b202fdffa616390 Mon Sep 17 00:00:00 2001
From: Pekka Paalanen <pq@....fi>
Date: Sun, 27 Apr 2008 00:00:33 +0300
Subject: [PATCH] mmiotrace: print overrun counts

Signed-off-by: Pekka Paalanen <pq@....fi>
---
 kernel/trace/trace_mmiotrace.c |   25 +++++++++++++++++++++++++
 1 files changed, 25 insertions(+), 0 deletions(-)

diff --git a/kernel/trace/trace_mmiotrace.c b/kernel/trace/trace_mmiotrace.c
index 6d2edbd..d0f649a 100644
--- a/kernel/trace/trace_mmiotrace.c
+++ b/kernel/trace/trace_mmiotrace.c
@@ -17,11 +17,13 @@ struct header_iter {
 };
 
 static struct trace_array *mmio_trace_array;
+static bool overrun_detected;
 
 static void mmio_reset_data(struct trace_array *tr)
 {
 	int cpu;
 
+	overrun_detected = false;
 	tr->time_start = ftrace_now(tr->cpu);
 
 	for_each_online_cpu(cpu)
@@ -124,12 +126,34 @@ static void mmio_close(struct trace_iterator *iter)
 	iter->private = NULL;
 }
 
+static unsigned long count_overruns(struct trace_iterator *iter)
+{
+	int cpu;
+	unsigned long cnt = 0;
+	for_each_online_cpu(cpu) {
+		cnt += iter->overrun[cpu];
+		iter->overrun[cpu] = 0;
+	}
+	return cnt;
+}
+
 static ssize_t mmio_read(struct trace_iterator *iter, struct file *filp,
 				char __user *ubuf, size_t cnt, loff_t *ppos)
 {
 	ssize_t ret;
 	struct header_iter *hiter = iter->private;
 	struct trace_seq *s = &iter->seq;
+	unsigned long n;
+
+	n = count_overruns(iter);
+	if (n) {
+		/* XXX: This is later than where events were lost. */
+		trace_seq_printf(s, "MARK 0.000000 Lost %lu events.\n", n);
+		if (!overrun_detected)
+			pr_warning("mmiotrace has lost events.\n");
+		overrun_detected = true;
+		goto print_out;
+	}
 
 	if (!hiter)
 		return 0;
@@ -142,6 +166,7 @@ static ssize_t mmio_read(struct trace_iterator *iter, struct file *filp,
 		iter->private = NULL;
 	}
 
+print_out:
 	ret = trace_seq_to_user(s, ubuf, cnt);
 	return (ret == -EBUSY) ? 0 : ret;
 }
-- 
1.5.3.7

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