[tracker/cpuaffinity] tracker-store: Avoid CPU hopping of main threads

[Jürg Billeter <juergbi src gnome org>]

commit 80c2fe73175a144d4bc3d9fae748669f935f9a00
Author: Jürg Billeter <j bitron ch>
Date:   Thu Jun 24 14:34:45 2010 +0200

    tracker-store: Avoid CPU hopping of main threads
    
    This improves update performance on SMP systems.

 src/tracker-store/tracker-store.c |   29 +++++++++++++++++++++++++++++
 1 files changed, 29 insertions(+), 0 deletions(-)
---
diff --git a/src/tracker-store/tracker-store.c b/src/tracker-store/tracker-store.c
index 729964a..6d9e1d3 100644
--- a/src/tracker-store/tracker-store.c
+++ b/src/tracker-store/tracker-store.c
@@ -21,6 +21,10 @@
 
 #include "config.h"
 
+#define _GNU_SOURCE
+#include <sched.h>
+#include <pthread.h>
+
 #include <unistd.h>
 #include <sys/types.h>
 
@@ -104,6 +108,9 @@ typedef struct {
 
 static GStaticPrivate private_key = G_STATIC_PRIVATE_INIT;
 
+/* cpu used for mainloop thread and main update/query thread */
+static int main_cpu;
+
 static void start_handler (TrackerStorePrivate *private);
 
 static void
@@ -446,6 +453,17 @@ pool_dispatch_cb (gpointer data,
 	TrackerStoreTask *task;
 	GThread *running_thread = g_thread_self ();
 
+	/* special task, only ever sent to main pool */
+	if (GPOINTER_TO_INT (data) == 1) {
+		cpu_set_t cpuset;
+		CPU_ZERO (&cpuset);
+		CPU_SET (main_cpu, &cpuset);
+
+		/* avoid cpu hopping which can lead to significantly worse performance */
+		pthread_setaffinity_np (pthread_self (), sizeof (cpu_set_t), &cpuset);
+		return;
+	}
+
 	private = user_data;
 	task = data;
 
@@ -604,6 +622,7 @@ tracker_store_init (void)
 	TrackerStorePrivate *private;
 	gint i;
 	const char *tmp;
+	cpu_set_t cpuset;
 
 	private = g_new0 (TrackerStorePrivate, 1);
 
@@ -630,6 +649,16 @@ tracker_store_init (void)
 	g_thread_pool_set_max_idle_time (15 * 1000);
 	g_thread_pool_set_max_unused_threads (2);
 
+	main_cpu = sched_getcpu ();
+	CPU_ZERO (&cpuset);
+	CPU_SET (main_cpu, &cpuset);
+
+	/* avoid cpu hopping which can lead to significantly worse performance */
+	pthread_setaffinity_np (pthread_self (), sizeof (cpu_set_t), &cpuset);
+	/* lock main update/query thread to same cpu to improve overall performance
+	   main loop thread is essentially idle during query execution */
+	g_thread_pool_push (private->main_pool, GINT_TO_POINTER (1), NULL);
+
 	g_static_private_set (&private_key,
 	                      private,
 	                      private_free);