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Date: Wed, 27 Jun 2012 20:52:43 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Dave Jones <davej@...hat.com>
Cc: Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: big allocation failure during tracing init.
On Fri, 2012-06-22 at 15:36 -0400, Dave Jones wrote:
> I guess the problem is on kernels built with CONFIG_MAXCPUS, struct trace_iterator
> can be pretty large due to this embedded in it..
>
> struct ring_buffer_iter *buffer_iter[NR_CPUS];
>
> Any thoughts on how to change that to a smaller dynamic data structure,
> without adding too much overhead to tracing ? (I'm assuming a linked-list walk
> for eg would be excessive?)
>
Does this patch fix it for you?
-- Steve
commit 0339abcabbef5f1fc57a8af046861a04e0a0ef9f
Author: Steven Rostedt <srostedt@...hat.com>
Date: Wed Jun 27 20:46:14 2012 -0400
tracing: Remove NR_CPUS array from trace_iterator
Replace the NR_CPUS array of buffer_iter from the trace_iterator
with an allocated array. This will just create an array of
possible CPUS instead of the max number specified.
Added a helper function called 'trace_buffer_iter()' that returns
the buffer_iter item or NULL if it is not defined or the array was
not allocated. Some routines do not require the array
(tracing_open_pipe() for one).
Reported-by: Dave Jones <davej@...hat.com>
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 1aff183..af961d6 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -65,7 +65,7 @@ struct trace_iterator {
void *private;
int cpu_file;
struct mutex mutex;
- struct ring_buffer_iter *buffer_iter[NR_CPUS];
+ struct ring_buffer_iter **buffer_iter;
unsigned long iter_flags;
/* trace_seq for __print_flags() and __print_symbolic() etc. */
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a8d5654..85073f9 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1710,9 +1710,11 @@ EXPORT_SYMBOL_GPL(trace_vprintk);
static void trace_iterator_increment(struct trace_iterator *iter)
{
+ struct ring_buffer_iter *buf_iter = trace_buffer_iter(iter, iter->cpu);
+
iter->idx++;
- if (iter->buffer_iter[iter->cpu])
- ring_buffer_read(iter->buffer_iter[iter->cpu], NULL);
+ if (buf_iter)
+ ring_buffer_read(buf_iter, NULL);
}
static struct trace_entry *
@@ -1720,7 +1722,7 @@ peek_next_entry(struct trace_iterator *iter, int cpu, u64 *ts,
unsigned long *lost_events)
{
struct ring_buffer_event *event;
- struct ring_buffer_iter *buf_iter = iter->buffer_iter[cpu];
+ struct ring_buffer_iter *buf_iter = trace_buffer_iter(iter, cpu);
if (buf_iter)
event = ring_buffer_iter_peek(buf_iter, ts);
@@ -1858,10 +1860,10 @@ void tracing_iter_reset(struct trace_iterator *iter, int cpu)
tr->data[cpu]->skipped_entries = 0;
- if (!iter->buffer_iter[cpu])
+ buf_iter = trace_buffer_iter(iter, cpu);
+ if (!buf_iter)
return;
- buf_iter = iter->buffer_iter[cpu];
ring_buffer_iter_reset(buf_iter);
/*
@@ -2207,13 +2209,15 @@ static enum print_line_t print_bin_fmt(struct trace_iterator *iter)
int trace_empty(struct trace_iterator *iter)
{
+ struct ring_buffer_iter *buf_iter;
int cpu;
/* If we are looking at one CPU buffer, only check that one */
if (iter->cpu_file != TRACE_PIPE_ALL_CPU) {
cpu = iter->cpu_file;
- if (iter->buffer_iter[cpu]) {
- if (!ring_buffer_iter_empty(iter->buffer_iter[cpu]))
+ buf_iter = trace_buffer_iter(iter, cpu);
+ if (buf_iter) {
+ if (!ring_buffer_iter_empty(buf_iter))
return 0;
} else {
if (!ring_buffer_empty_cpu(iter->tr->buffer, cpu))
@@ -2223,8 +2227,9 @@ int trace_empty(struct trace_iterator *iter)
}
for_each_tracing_cpu(cpu) {
- if (iter->buffer_iter[cpu]) {
- if (!ring_buffer_iter_empty(iter->buffer_iter[cpu]))
+ buf_iter = trace_buffer_iter(iter, cpu);
+ if (buf_iter) {
+ if (!ring_buffer_iter_empty(buf_iter))
return 0;
} else {
if (!ring_buffer_empty_cpu(iter->tr->buffer, cpu))
@@ -2383,6 +2388,8 @@ __tracing_open(struct inode *inode, struct file *file)
if (!iter)
return ERR_PTR(-ENOMEM);
+ iter->buffer_iter = kzalloc(sizeof(*iter->buffer_iter) * num_possible_cpus(),
+ GFP_KERNEL);
/*
* We make a copy of the current tracer to avoid concurrent
* changes on it while we are reading.
@@ -2443,6 +2450,7 @@ __tracing_open(struct inode *inode, struct file *file)
fail:
mutex_unlock(&trace_types_lock);
kfree(iter->trace);
+ kfree(iter->buffer_iter);
seq_release_private(inode, file);
return ERR_PTR(-ENOMEM);
}
@@ -2483,6 +2491,7 @@ static int tracing_release(struct inode *inode, struct file *file)
mutex_destroy(&iter->mutex);
free_cpumask_var(iter->started);
kfree(iter->trace);
+ kfree(iter->buffer_iter);
seq_release_private(inode, file);
return 0;
}
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 5aec220..55e1f7f 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -317,6 +317,14 @@ struct tracer {
#define TRACE_PIPE_ALL_CPU -1
+static inline struct ring_buffer_iter *
+trace_buffer_iter(struct trace_iterator *iter, int cpu)
+{
+ if (iter->buffer_iter && iter->buffer_iter[cpu])
+ return iter->buffer_iter[cpu];
+ return NULL;
+}
+
int tracer_init(struct tracer *t, struct trace_array *tr);
int tracing_is_enabled(void);
void trace_wake_up(void);
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index a7d2a4c..ce27c8b 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -538,7 +538,7 @@ get_return_for_leaf(struct trace_iterator *iter,
next = &data->ret;
} else {
- ring_iter = iter->buffer_iter[iter->cpu];
+ ring_iter = trace_buffer_iter(iter, iter->cpu);
/* First peek to compare current entry and the next one */
if (ring_iter)
--
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