Use deferred ring buffer allocation in new trace buffer instances by
copying the behavior of the deferred allocation of global_trace's buffer.
Without this, each new trace buffer instance will attempt to allocate
num_cpus * TRACE_BUF_SIZE_DEFAULT bytes for the ring buffer, which might
fail on a system with many cores. If this fails, the new instance is not
created, precluding the user from setting a smaller buffer for which
allocation might succeed.
Cc: David Sharp <dhsh...@google.com>
Cc: Vaibhav Nagarnaik <vnagarn...@google.com>
Cc: Alexander Z Lam <lambchop...@gmail.com>
Signed-off-by: Alexander Z Lam <a...@google.com>
---
kernel/trace/trace.c | 92 +++++++++++++++++++++++++--------------------
kernel/trace/trace.h | 5 ++-
kernel/trace/trace_events.c | 8 ++--
3 files changed, 58 insertions(+), 47 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 9e42e48..e0b0d2a 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -44,12 +44,6 @@
#include "trace_output.h"
/*
- * On boot up, the ring buffer is set to the minimum size, so that
- * we do not waste memory on systems that are not using tracing.
- */
-bool ring_buffer_expanded;
-
-/*
* We need to change this state when a selftest is running.
* A selftest will lurk into the ring-buffer to count the
* entries inserted during the selftest although some concurrent
@@ -86,6 +80,20 @@ static int dummy_set_flag(u32 old_flags, u32 bit, int set)
static DEFINE_PER_CPU(bool, trace_cmdline_save);
/*
+ * The global_trace is the descriptor that holds the tracing
+ * buffers for the live tracing. For each CPU, it contains
+ * a link list of pages that will store trace entries. The
+ * page descriptor of the pages in the memory is used to hold
+ * the link list by linking the lru item in the page descriptor
+ * to each of the pages in the buffer per CPU.
+ *
+ * For each active CPU there is a data field that holds the
+ * pages for the buffer for that CPU. Each CPU has the same number
+ * of pages allocated for its buffer.
+ */
+static struct trace_array global_trace;
+
+/*
* Kill all tracing for good (never come back).
* It is initialized to 1 but will turn to zero if the initialization
* of the tracer is successful. But that is the only place that sets
@@ -131,7 +139,7 @@ static int __init set_cmdline_ftrace(char *str)
strlcpy(bootup_tracer_buf, str, MAX_TRACER_SIZE);
default_bootup_tracer = bootup_tracer_buf;
/* We are using ftrace early, expand it */
- ring_buffer_expanded = true;
+ global_trace.buffer_expanded = true;
return 1;
}
__setup("ftrace=", set_cmdline_ftrace);
@@ -163,7 +171,7 @@ static int __init boot_alloc_snapshot(char *str)
{
allocate_snapshot = true;
/* We also need the main ring buffer expanded */
- ring_buffer_expanded = true;
+ global_trace.buffer_expanded = true;
return 1;
}
__setup("alloc_snapshot", boot_alloc_snapshot);
@@ -188,20 +196,6 @@ unsigned long long ns2usecs(cycle_t nsec)
return nsec;
}
-/*
- * The global_trace is the descriptor that holds the tracing
- * buffers for the live tracing. For each CPU, it contains
- * a link list of pages that will store trace entries. The
- * page descriptor of the pages in the memory is used to hold
- * the link list by linking the lru item in the page descriptor
- * to each of the pages in the buffer per CPU.
- *
- * For each active CPU there is a data field that holds the
- * pages for the buffer for that CPU. Each CPU has the same number
- * of pages allocated for its buffer.
- */
-static struct trace_array global_trace;
-
LIST_HEAD(ftrace_trace_arrays);
int filter_current_check_discard(struct ring_buffer *buffer,
@@ -988,7 +982,7 @@ static int run_tracer_selftest(struct tracer *type)
#ifdef CONFIG_TRACER_MAX_TRACE
if (type->use_max_tr) {
/* If we expanded the buffers, make sure the max is expanded
too */
- if (ring_buffer_expanded)
+ if (tr->buffer_expanded)
ring_buffer_resize(tr->max_buffer.buffer,
trace_buf_size,
RING_BUFFER_ALL_CPUS);
tr->allocated_snapshot = true;
@@ -1014,7 +1008,7 @@ static int run_tracer_selftest(struct tracer *type)
tr->allocated_snapshot = false;
/* Shrink the max buffer again */
- if (ring_buffer_expanded)
+ if (tr->buffer_expanded)
ring_buffer_resize(tr->max_buffer.buffer, 1,
RING_BUFFER_ALL_CPUS);
}
@@ -1863,7 +1857,7 @@ void trace_printk_init_buffers(void)
pr_info("ftrace: Allocated trace_printk buffers\n");
/* Expand the buffers to set size */
- tracing_update_buffers();
+ tracing_update_buffers(&global_trace);
buffers_allocated = 1;
@@ -3538,7 +3532,7 @@ static int __tracing_resize_ring_buffer(struct
trace_array *tr,
* we use the size that was given, and we can forget about
* expanding it later.
*/
- ring_buffer_expanded = true;
+ tr->buffer_expanded = true;
/* May be called before buffers are initialized */
if (!tr->trace_buffer.buffer)
@@ -3578,11 +3572,6 @@ static int __tracing_resize_ring_buffer(struct
trace_array *tr,
return ret;
}
- if (cpu == RING_BUFFER_ALL_CPUS)
- set_buffer_entries(&tr->max_buffer, size);
- else
- per_cpu_ptr(tr->max_buffer.data, cpu)->entries = size;
-
out:
#endif /* CONFIG_TRACER_MAX_TRACE */
@@ -3621,6 +3610,21 @@ out:
/**
+ * set_global_ring_buffer_expanded
+ *
+ * Sets the buffer_expanded flag for global_trace, causing the next
+ * (re)allocation of the global tracing events ring buffer to use the expanded
+ * size. During boot, this causes the buffer to assume TRACE_BUF_SIZE_DEFAULT
+ * and after that, to assume the user-set size instead of 1.
+ */
+void set_global_ring_buffer_expanded()
+{
+ mutex_lock(&trace_types_lock);
+ global_trace.buffer_expanded = true;
+ mutex_unlock(&trace_types_lock);
+}
+
+/**
* tracing_update_buffers - used by tracing facility to expand ring buffers
*
* To save on memory when the tracing is never used on a system with it
@@ -3629,14 +3633,16 @@ out:
* to their default size.
*
* This function is to be called when a tracer is about to be used.
+ *
+ * @tr The trace_array which needs its buffers expanded
*/
-int tracing_update_buffers(void)
+int tracing_update_buffers(struct trace_array *tr)
{
int ret = 0;
mutex_lock(&trace_types_lock);
- if (!ring_buffer_expanded)
- ret = __tracing_resize_ring_buffer(&global_trace,
trace_buf_size,
+ if (!tr->buffer_expanded)
+ ret = __tracing_resize_ring_buffer(tr, trace_buf_size,
RING_BUFFER_ALL_CPUS);
mutex_unlock(&trace_types_lock);
@@ -3663,7 +3669,7 @@ static int tracing_set_tracer(const char *buf)
mutex_lock(&trace_types_lock);
- if (!ring_buffer_expanded) {
+ if (!tr->buffer_expanded) {
ret = __tracing_resize_ring_buffer(tr, trace_buf_size,
RING_BUFFER_ALL_CPUS);
if (ret < 0)
@@ -4243,7 +4249,7 @@ tracing_entries_read(struct file *filp, char __user *ubuf,
}
if (buf_size_same) {
- if (!ring_buffer_expanded)
+ if (!tr->buffer_expanded)
r = sprintf(buf, "%lu (expanded: %lu)\n",
size >> 10,
trace_buf_size >> 10);
@@ -4300,10 +4306,10 @@ tracing_total_entries_read(struct file *filp, char
__user *ubuf,
mutex_lock(&trace_types_lock);
for_each_tracing_cpu(cpu) {
size += per_cpu_ptr(tr->trace_buffer.data, cpu)->entries >> 10;
- if (!ring_buffer_expanded)
+ if (!tr->buffer_expanded)
expanded_size += trace_buf_size >> 10;
}
- if (ring_buffer_expanded)
+ if (tr->buffer_expanded)
r = sprintf(buf, "%lu\n", size);
else
r = sprintf(buf, "%lu (expanded: %lu)\n", size, expanded_size);
@@ -4566,7 +4572,7 @@ tracing_snapshot_write(struct file *filp, const char
__user *ubuf, size_t cnt,
unsigned long val;
int ret;
- ret = tracing_update_buffers();
+ ret = tracing_update_buffers(tr);
if (ret < 0)
return ret;
@@ -5780,7 +5786,11 @@ static int new_instance_create(const char *name)
INIT_LIST_HEAD(&tr->systems);
INIT_LIST_HEAD(&tr->events);
- if (allocate_trace_buffers(tr, trace_buf_size) < 0)
+ /* Allocate with small size to avoid failure to allocate buffers on
+ * many-core systems. The ring buffer will be dynamically expanded via
+ * tracing_update_buffers when the user attempts to trace, or the user
+ * can set the size using buffer_size_kb */
+ if (allocate_trace_buffers(tr, 1) < 0)
goto out_free_tr;
/* Holder for file callbacks */
@@ -6217,7 +6227,7 @@ __init static int tracer_alloc_buffers(void)
trace_printk_init_buffers();
/* To save memory, keep the ring buffer size to its minimum */
- if (ring_buffer_expanded)
+ if (global_trace.buffer_expanded)
ring_buf_size = trace_buf_size;
else
ring_buf_size = 1;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 20572ed..3de07e0 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -195,6 +195,7 @@ struct trace_array {
struct trace_buffer max_buffer;
bool allocated_snapshot;
#endif
+ bool buffer_expanded;
int buffer_disabled;
struct trace_cpu trace_cpu; /* place holder */
#ifdef CONFIG_FTRACE_SYSCALLS
@@ -657,7 +658,6 @@ extern int DYN_FTRACE_TEST_NAME(void);
#define DYN_FTRACE_TEST_NAME2 trace_selftest_dynamic_test_func2
extern int DYN_FTRACE_TEST_NAME2(void);
-extern bool ring_buffer_expanded;
extern bool tracing_selftest_disabled;
DECLARE_PER_CPU(int, ftrace_cpu_disabled);
@@ -896,8 +896,9 @@ static inline void trace_branch_disable(void)
}
#endif /* CONFIG_BRANCH_TRACER */
+void set_global_ring_buffer_expanded(void);
/* set ring buffers to default size if not already done so */
-int tracing_update_buffers(void);
+int tracing_update_buffers(struct trace_array *tr);
/* trace event type bit fields, not numeric */
enum {
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index f57b015..6db3290 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -495,7 +495,7 @@ ftrace_event_write(struct file *file, const char __user
*ubuf,
if (!cnt)
return 0;
- ret = tracing_update_buffers();
+ ret = tracing_update_buffers(tr);
if (ret < 0)
return ret;
@@ -649,7 +649,7 @@ event_enable_write(struct file *filp, const char __user
*ubuf, size_t cnt,
if (ret)
return ret;
- ret = tracing_update_buffers();
+ ret = tracing_update_buffers(file->tr);
if (ret < 0)
return ret;
@@ -730,7 +730,7 @@ system_enable_write(struct file *filp, const char __user
*ubuf, size_t cnt,
if (ret)
return ret;
- ret = tracing_update_buffers();
+ ret = tracing_update_buffers(dir->tr);
if (ret < 0)
return ret;
@@ -2219,7 +2219,7 @@ static char bootup_event_buf[COMMAND_LINE_SIZE]
__initdata;
static __init int setup_trace_event(char *str)
{
strlcpy(bootup_event_buf, str, COMMAND_LINE_SIZE);
- ring_buffer_expanded = true;
+ set_global_ring_buffer_expanded();
tracing_selftest_disabled = true;
return 1;
--
1.8.3
--
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