ftrace: nmi update statistics

Impact: add more debug info to /debugfs/tracing/dyn_ftrace_total_info

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>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index fe5f859130b5841d68b55b2861e7b506921ccd8e..6685b0fc1b4401264dfc9670f05121d581693205 100644 (file)
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -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

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a610ca77155891f45d625fe2c5927cae4a3fa8dd..bc36febc0771afc4b245e92f17d2112b0469198f 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2815,22 +2815,39 @@ static struct file_operations tracing_mark_fops = {
 
 #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);
 
-       return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+       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 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
 
@@ -2939,7 +2956,7 @@ static __init int tracer_init_debugfs(void)
 #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");