[PATCH 2/2] ftrace: nmi update statistics

Steven Rostedt
2008-10-30T20:12:24Z

[-- Attachment #1: ftrace-count-nmi-writes.patch --]
[-- Type: text/plain, Size: 3349 bytes --]

This patch adds dynamic ftrace NMI update statistics to the
/debugfs/tracing/dyn_ftrace_total_info stat file.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
arch/x86/kernel/ftrace.c | 26 ++++++++++++++++++++++++--
kernel/trace/trace.c | 31 ++++++++++++++++++++++++-------
2 files changed, 48 insertions(+), 9 deletions(-)

Index: linux-tip.git/arch/x86/kernel/ftrace.c
===================================================================
--- linux-tip.git.orig/arch/x86/kernel/ftrace.c 2008-10-30 15:30:12.000000000 -0400
+++ linux-tip.git/arch/x86/kernel/ftrace.c 2008-10-30 15:51:51.000000000 -0400
@@ -91,6 +91,19 @@ static int mod_code_write;
static void *mod_code_ip;
static void *mod_code_newcode;

+static int nmi_wait_count;
+static atomic_t nmi_update_count;
+
+int ftrace_arch_read_dyn_info(char *buf, int size)
+{
+ int r;
+
+ r = snprintf(buf, size, "%u %u",
+ nmi_wait_count,
+ atomic_read(&nmi_update_count));
+ return r;
+}
+
static void ftrace_mod_code(void)
{
/*
@@ -109,8 +122,10 @@ void ftrace_nmi_enter(void)
atomic_inc(&in_nmi);
/* Must have in_nmi seen before reading write flag */
smp_mb();
- if (mod_code_write)
+ if (mod_code_write) {
ftrace_mod_code();
+ atomic_inc(&nmi_update_count);
+ }
}

void ftrace_nmi_exit(void)
@@ -122,8 +137,15 @@ void ftrace_nmi_exit(void)

static void wait_for_nmi(void)
{
- while (atomic_read(&in_nmi))
+ int waited = 0;
+
+ while (atomic_read(&in_nmi)) {
+ waited = 1;
cpu_relax();
+ }
+
+ if (waited)
+ nmi_wait_count++;
}

static int
Index: linux-tip.git/kernel/trace/trace.c
===================================================================
--- linux-tip.git.orig/kernel/trace/trace.c 2008-10-30 15:18:45.000000000 -0400
+++ linux-tip.git/kernel/trace/trace.c 2008-10-30 15:51:51.000000000 -0400
@@ -2837,22 +2837,39 @@ static struct file_operations tracing_ma

#ifdef CONFIG_DYNAMIC_FTRACE

+#define DYN_INFO_BUF_SIZE 1023
+static char ftrace_dyn_info_buffer[DYN_INFO_BUF_SIZE+1];
+static DEFINE_MUTEX(dyn_info_mutex);
+
+int __weak ftrace_arch_read_dyn_info(char *buf, int size)
+{
+ return 0;
+}
+
static ssize_t
-tracing_read_long(struct file *filp, char __user *ubuf,
+tracing_read_dyn_info(struct file *filp, char __user *ubuf,
size_t cnt, loff_t *ppos)
{
unsigned long *p = filp->private_data;
- char buf[64];
+ char *buf = ftrace_dyn_info_buffer;
int r;

- r = sprintf(buf, "%ld\n", *p);
+ mutex_lock(&dyn_info_mutex);
+ r = sprintf(buf, "%ld ", *p);
+
+ r += ftrace_arch_read_dyn_info(buf+r, DYN_INFO_BUF_SIZE-r);
+ buf[r++] = '\n';
+
+ r = simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+
+ mutex_unlock(&dyn_info_mutex);

- return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+ return r;
}

-static struct file_operations tracing_read_long_fops = {
+static struct file_operations tracing_dyn_info_fops = {
.open = tracing_open_generic,
- .read = tracing_read_long,
+ .read = tracing_read_dyn_info,
};
#endif

@@ -2961,7 +2978,7 @@ static __init int tracer_init_debugfs(vo
#ifdef CONFIG_DYNAMIC_FTRACE
entry = debugfs_create_file("dyn_ftrace_total_info", 0444, d_tracer,
&ftrace_update_tot_cnt,
- &tracing_read_long_fops);
+ &tracing_dyn_info_fops);
if (!entry)
pr_warning("Could not create debugfs "
"'dyn_ftrace_total_info' entry\n");

--