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Subject[PATCH] lockdep: Add nr_save_trace_invocations counter
NOT FOR INCLUSION

I created this patch as a result of Peter Zilstra's request to get more
info from lockdep. This patch is not for inclusion, at least in its
present form, because it adds some redunant info to /proc/lockdep_stats

However, some of the fields are new, and it is worth examining, and / or
applying if you are looking at the MAX_STACK_TRACE_ENTRIES too big
problem.

I generated this patch against a recent tip/master but it applies without
conflicts to the latest rt kernel as well. Comments are welcome, in fact
they are appreciated.

From 5181c0296dd1549e4e706ff25a4cd81a1d90137d Mon Sep 17 00:00:00 2001
From: John Kacur <jkacur@redhat.com>
Date: Thu, 22 Apr 2010 17:02:42 +0200
Subject: [PATCH] lockdep: Add nr_save_trace_invocations counter

Add the nr_save_trace_invocations counter which counts the number of
time save_trace() is invoked when relevant for trace enteries.

This means, those invocations from mark_lock() and add_lock_to_list()

When called from mark_lock() we break it down into LOCKSTATE categories.

Signed-off-by: John Kacur <jkacur@redhat.com>
---
kernel/lockdep.c | 20 ++++++++++++++++++++
kernel/lockdep_internals.h | 2 ++
kernel/lockdep_proc.c | 23 +++++++++++++++++++++++
3 files changed, 45 insertions(+), 0 deletions(-)

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 78325f8..f921576 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -371,6 +371,10 @@ static int verbose(struct lock_class *class)
unsigned long nr_stack_trace_entries;
static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];

+/* Calls to save_trace() from mark_lock() and add_lock_to_list() only*/
+unsigned long nr_save_trace_invocations;
+unsigned long nr_save_trace_invocations_type[LOCK_USAGE_STATES];
+
static int save_trace(struct stack_trace *trace)
{
trace->nr_entries = 0;
@@ -410,6 +414,19 @@ static int save_trace(struct stack_trace *trace)
return 1;
}

+/*
+ * This function is only called from mark_lock() and add_lock_to_list()
+ * which are only called when holding the graph_lock. This counter
+ * piggybacks off of that lock
+ */
+static void inc_save_trace_invocations(enum lock_usage_bit new_bit)
+{
+ nr_save_trace_invocations++;
+ if (WARN_ON(new_bit >= LOCK_USAGE_STATES))
+ return;
+ nr_save_trace_invocations_type[new_bit]++;
+}
+
unsigned int nr_hardirq_chains;
unsigned int nr_softirq_chains;
unsigned int nr_process_chains;
@@ -449,6 +466,7 @@ static const char *usage_str[] =
#define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
#include "lockdep_states.h"
#undef LOCKDEP_STATE
+#undef __USAGE
[LOCK_USED] = "INITIAL USE",
};

@@ -816,6 +834,7 @@ static int add_lock_to_list(struct lock_class *class, struct lock_class *this,
if (!entry)
return 0;

+ nr_save_trace_invocations++;
if (!save_trace(&entry->trace))
return 0;

@@ -2615,6 +2634,7 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,

hlock_class(this)->usage_mask |= new_mask;

+ inc_save_trace_invocations(new_bit);
if (!save_trace(hlock_class(this)->usage_traces + new_bit))
return 0;

diff --git a/kernel/lockdep_internals.h b/kernel/lockdep_internals.h
index 8d7d4b6..6149358 100644
--- a/kernel/lockdep_internals.h
+++ b/kernel/lockdep_internals.h
@@ -84,6 +84,8 @@ extern unsigned long nr_list_entries;
extern unsigned long nr_lock_chains;
extern int nr_chain_hlocks;
extern unsigned long nr_stack_trace_entries;
+extern unsigned long nr_save_trace_invocations;
+extern unsigned long nr_save_trace_invocations_type[LOCK_USAGE_STATES];

extern unsigned int nr_hardirq_chains;
extern unsigned int nr_softirq_chains;
diff --git a/kernel/lockdep_proc.c b/kernel/lockdep_proc.c
index 59b76c8..ef5f372 100644
--- a/kernel/lockdep_proc.c
+++ b/kernel/lockdep_proc.c
@@ -215,8 +215,24 @@ static void lockdep_stats_debug_show(struct seq_file *m)
#endif
}

+#define __USAGE(__STATE) \
+[LOCK_USED_IN_##__STATE] = "LOCK_USED_IN_"__stringify(__STATE), \
+[LOCK_ENABLED_##__STATE] = "LOCK_ENABLED_"__stringify(__STATE), \
+[LOCK_USED_IN_##__STATE##_READ] = "LOCK_USED_IN_"__stringify(__STATE)"_READ", \
+[LOCK_ENABLED_##__STATE##_READ] = "LOCK_ENABLED_"__stringify(__STATE)"_READ",
+
+static const char *lockstate_tostr[] =
+{
+#define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
+#include "lockdep_states.h"
+#undef LOCKDEP_STATE
+#undef __USAGE
+ [LOCK_USED] = "LOCK_USED",
+};
+
static int lockdep_stats_show(struct seq_file *m, void *v)
{
+ int bit;
struct lock_class *class;
unsigned long nr_unused = 0, nr_uncategorized = 0,
nr_irq_safe = 0, nr_irq_unsafe = 0,
@@ -307,6 +323,13 @@ static int lockdep_stats_show(struct seq_file *m, void *v)
nr_process_chains);
seq_printf(m, " stack-trace entries: %11lu [max: %lu]\n",
nr_stack_trace_entries, MAX_STACK_TRACE_ENTRIES);
+ seq_printf(m, " stack-trace invocations: %lu\n",
+ nr_save_trace_invocations);
+
+ for (bit=0; bit < LOCK_USAGE_STATES; bit++)
+ seq_printf(m, "\t%s: %lu\n", lockstate_tostr[bit],
+ nr_save_trace_invocations_type[bit]);
+
seq_printf(m, " combined max dependencies: %11u\n",
(nr_hardirq_chains + 1) *
(nr_softirq_chains + 1) *
--
1.6.6.1


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