From 59987a623a2792ec836438249512da51f203e33a Mon Sep 17 00:00:00 2001
From: Ben Pfaff <blp@nicira.com>
Date: Thu, 25 Apr 2013 16:42:04 -0700
Subject: [PATCH] system-stats: Move into separate thread.

Signed-off-by: Ben Pfaff <blp@nicira.com>
---
 vswitchd/system-stats.c | 106 ++++++++++++++++++++++++++++++++--------
 1 file changed, 85 insertions(+), 21 deletions(-)

diff --git a/vswitchd/system-stats.c b/vswitchd/system-stats.c
index e7c1d7311..b1642284c 100644
--- a/vswitchd/system-stats.c
+++ b/vswitchd/system-stats.c
@@ -35,7 +35,9 @@
 #include "dirs.h"
 #include "dynamic-string.h"
 #include "json.h"
+#include "latch.h"
 #include "ofpbuf.h"
+#include "ovs-thread.h"
 #include "poll-loop.h"
 #include "shash.h"
 #include "smap.h"
@@ -504,17 +506,33 @@ get_filesys_stats(struct smap *stats OVS_UNUSED)
 
 #define SYSTEM_STATS_INTERVAL (5 * 1000) /* In milliseconds. */
 
-/* The next time to wake up, or LLONG_MAX if stats are disabled. */
-static long long int next_refresh = LLONG_MAX;
+static pthread_mutex_t mutex = PTHREAD_ADAPTIVE_MUTEX_INITIALIZER;
+static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
+static struct latch latch;
+static bool enabled;
+static bool started;
+static struct smap *system_stats;
+
+static void *system_stats_thread_func(void *);
+static void discard_stats(void);
 
 /* Enables or disables system stats collection, according to 'enable'. */
 void
 system_stats_enable(bool enable)
 {
-    if (!enable) {
-        next_refresh = LLONG_MAX;
-    } else if (next_refresh == LLONG_MAX) {
-        next_refresh = time_msec();
+    if (enabled != enable) {
+        xpthread_mutex_lock(&mutex);
+        if (enable) {
+            if (!started) {
+                xpthread_create(NULL, NULL, system_stats_thread_func, NULL);
+                latch_init(&latch);
+                started = true;
+            }
+            discard_stats();
+            xpthread_cond_signal(&cond);
+        }
+        enabled = enable;
+        xpthread_mutex_unlock(&mutex);
     }
 }
 
@@ -529,23 +547,22 @@ system_stats_enable(bool enable)
 struct smap *
 system_stats_run(void)
 {
-    if (time_msec() >= next_refresh) {
-        struct smap *stats;
+    struct smap *stats = NULL;
 
-        stats = xmalloc(sizeof *stats);
-        smap_init(stats);
-        get_cpu_cores(stats);
-        get_load_average(stats);
-        get_memory_stats(stats);
-        get_process_stats(stats);
-        get_filesys_stats(stats);
-
-        next_refresh = time_msec() + SYSTEM_STATS_INTERVAL;
+    xpthread_mutex_lock(&mutex);
+    if (system_stats) {
+        latch_poll(&latch);
 
-        return stats;
+        if (enabled) {
+            stats = system_stats;
+            system_stats = NULL;
+        } else {
+            discard_stats();
+        }
     }
+    xpthread_mutex_unlock(&mutex);
 
-    return NULL;
+    return stats;
 }
 
 /* Causes poll_block() to wake up when system_stats_run() needs to be
@@ -553,7 +570,54 @@ system_stats_run(void)
 void
 system_stats_wait(void)
 {
-    if (next_refresh != LLONG_MAX) {
-        poll_timer_wait_until(next_refresh);
+    if (enabled) {
+        latch_wait(&latch);
+    }
+}
+
+static void
+discard_stats(void)
+{
+    if (system_stats) {
+        smap_destroy(system_stats);
+        free(system_stats);
+        system_stats = NULL;
+    }
+}
+
+static void * NO_RETURN
+system_stats_thread_func(void *arg OVS_UNUSED)
+{
+    pthread_detach(pthread_self());
+
+    for (;;) {
+        long long int next_refresh;
+        struct smap *stats;
+
+        xpthread_mutex_lock(&mutex);
+        while (!enabled) {
+            xpthread_cond_wait(&cond, &mutex);
+        }
+        xpthread_mutex_unlock(&mutex);
+
+        stats = xmalloc(sizeof *stats);
+        smap_init(stats);
+        get_cpu_cores(stats);
+        get_load_average(stats);
+        get_memory_stats(stats);
+        get_process_stats(stats);
+        get_filesys_stats(stats);
+
+        xpthread_mutex_lock(&mutex);
+        discard_stats();
+        system_stats = stats;
+        latch_set(&latch);
+        xpthread_mutex_unlock(&mutex);
+
+        next_refresh = time_msec() + SYSTEM_STATS_INTERVAL;
+        do {
+            poll_timer_wait_until(next_refresh);
+            poll_block();
+        } while (time_msec() < next_refresh);
     }
 }
-- 
2.20.1