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Subject[PATCH v2 3/3] mmiotrace: count events lost due to not recording
From 7b1371189e38609f74c68a7b83c0a7a038a9b712 Mon Sep 17 00:00:00 2001
From: Pekka Paalanen <pq@iki.fi>
Date: Tue, 6 Jan 2009 13:57:11 +0200
Subject: [PATCH] mmiotrace: count events lost due to not recording

Impact: enhances lost events counting in mmiotrace

The tracing framework, or the ring buffer facility it uses, has a switch
to stop recording data. When recording is off, the trace events will be
lost. The framework does not count these, so mmiotrace has to count them
itself.

Signed-off-by: Pekka Paalanen <pq@iki.fi>
---
kernel/trace/trace_mmiotrace.c | 14 ++++++++++----
1 files changed, 10 insertions(+), 4 deletions(-)
diff --git a/kernel/trace/trace_mmiotrace.c b/kernel/trace/trace_mmiotrace.c
index fcec59f..621c8c3 100644
--- a/kernel/trace/trace_mmiotrace.c
+++ b/kernel/trace/trace_mmiotrace.c
@@ -9,6 +9,7 @@
#include <linux/kernel.h>
#include <linux/mmiotrace.h>
#include <linux/pci.h>
+#include <asm/atomic.h>

#include "trace.h"
#include "trace_output.h"
@@ -20,6 +21,7 @@ struct header_iter {
static struct trace_array *mmio_trace_array;
static bool overrun_detected;
static unsigned long prev_overruns;
+static atomic_t dropped_count;

static void mmio_reset_data(struct trace_array *tr)
{
@@ -122,11 +124,11 @@ static void mmio_close(struct trace_iterator *iter)

static unsigned long count_overruns(struct trace_iterator *iter)
{
- unsigned long cnt = 0;
+ unsigned long cnt = atomic_xchg(&dropped_count, 0);
unsigned long over = ring_buffer_overruns(iter->tr->buffer);

if (over > prev_overruns)
- cnt = over - prev_overruns;
+ cnt += over - prev_overruns;
prev_overruns = over;
return cnt;
}
@@ -308,8 +310,10 @@ static void __trace_mmiotrace_rw(struct trace_array *tr,

event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry),
&irq_flags);
- if (!event)
+ if (!event) {
+ atomic_inc(&dropped_count);
return;
+ }
entry = ring_buffer_event_data(event);
tracing_generic_entry_update(&entry->ent, 0, preempt_count());
entry->ent.type = TRACE_MMIO_RW;
@@ -336,8 +340,10 @@ static void __trace_mmiotrace_map(struct trace_array *tr,

event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry),
&irq_flags);
- if (!event)
+ if (!event) {
+ atomic_inc(&dropped_count);
return;
+ }
entry = ring_buffer_event_data(event);
tracing_generic_entry_update(&entry->ent, 0, preempt_count());
entry->ent.type = TRACE_MMIO_MAP;
--
1.6.0.6


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