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Subject[patch 7/11] net: Use bigrefs for net_device.refcount
The net_device has a refcnt used to keep track of it's uses.
This is used at the time of unregistering the network device
(module unloading ..) (see netdev_wait_allrefs) .
For loopback_dev , this refcnt increment/decrement is causing
unnecessary traffic on the interlink for NUMA system
affecting it's performance. This patch improves tbench numbers by 6% on a
8way x86 Xeon (x445).

This patch is dependent on the bigref patch

Signed-off-by : Niraj Kumar <nirajk@calsoftinc.com>
Signed-off-by : Shai Fultheim <shai@scalex86.org>
Signed-off-by : Ravikiran Thirumalai <kiran@scalex86.org>

Index: alloc_percpu-2.6.13/drivers/net/loopback.c
===================================================================
--- alloc_percpu-2.6.13.orig/drivers/net/loopback.c 2005-08-28 16:41:01.000000000 -0700
+++ alloc_percpu-2.6.13/drivers/net/loopback.c 2005-09-12 12:04:25.000000000 -0700
@@ -226,6 +226,12 @@
loopback_dev.priv = stats;
loopback_dev.get_stats = &get_stats;
}
+
+ /*
+ * This is the only struct net_device not allocated by alloc_netdev
+ * So explicitly init the bigref hanging off loopback_dev
+ */
+ bigref_init(&loopback_dev.netdev_refcnt);

return register_netdev(&loopback_dev);
};
Index: alloc_percpu-2.6.13/include/linux/netdevice.h
===================================================================
--- alloc_percpu-2.6.13.orig/include/linux/netdevice.h 2005-08-28 16:41:01.000000000 -0700
+++ alloc_percpu-2.6.13/include/linux/netdevice.h 2005-09-12 11:54:21.000000000 -0700
@@ -37,6 +37,7 @@
#include <linux/config.h>
#include <linux/device.h>
#include <linux/percpu.h>
+#include <linux/bigref.h>

struct divert_blk;
struct vlan_group;
@@ -377,7 +378,7 @@
/* device queue lock */
spinlock_t queue_lock;
/* Number of references to this device */
- atomic_t refcnt;
+ struct bigref netdev_refcnt;
/* delayed register/unregister */
struct list_head todo_list;
/* device name hash chain */
@@ -677,11 +678,11 @@

static inline void dev_put(struct net_device *dev)
{
- atomic_dec(&dev->refcnt);
+ bigref_put(&dev->netdev_refcnt, NULL);
}

-#define __dev_put(dev) atomic_dec(&(dev)->refcnt)
-#define dev_hold(dev) atomic_inc(&(dev)->refcnt)
+#define __dev_put(dev) bigref_put(&(dev)->netdev_refcnt, NULL);
+#define dev_hold(dev) bigref_get(&(dev)->netdev_refcnt);

/* Carrier loss detection, dial on demand. The functions netif_carrier_on
* and _off may be called from IRQ context, but it is caller
Index: alloc_percpu-2.6.13/net/core/dev.c
===================================================================
--- alloc_percpu-2.6.13.orig/net/core/dev.c 2005-08-28 16:41:01.000000000 -0700
+++ alloc_percpu-2.6.13/net/core/dev.c 2005-09-12 11:54:21.000000000 -0700
@@ -2658,6 +2658,7 @@
goto out;

dev->iflink = -1;
+ bigref_set(&dev->netdev_refcnt, 0);

/* Init, if this function is available */
if (dev->init) {
@@ -2808,7 +2809,7 @@
unsigned long rebroadcast_time, warning_time;

rebroadcast_time = warning_time = jiffies;
- while (atomic_read(&dev->refcnt) != 0) {
+ while ( bigref_val(&dev->netdev_refcnt) != 0) {
if (time_after(jiffies, rebroadcast_time + 1 * HZ)) {
rtnl_shlock();

@@ -2838,7 +2839,7 @@
printk(KERN_EMERG "unregister_netdevice: "
"waiting for %s to become free. Usage "
"count = %d\n",
- dev->name, atomic_read(&dev->refcnt));
+ dev->name, bigref_val(&dev->netdev_refcnt));
warning_time = jiffies;
}
}
@@ -2909,7 +2910,7 @@
netdev_wait_allrefs(dev);

/* paranoia */
- BUG_ON(atomic_read(&dev->refcnt));
+ BUG_ON(bigref_val(&dev->netdev_refcnt));
BUG_TRAP(!dev->ip_ptr);
BUG_TRAP(!dev->ip6_ptr);
BUG_TRAP(!dev->dn_ptr);
@@ -2969,6 +2970,7 @@

setup(dev);
strcpy(dev->name, name);
+ bigref_init(&dev->netdev_refcnt);
return dev;
}
EXPORT_SYMBOL(alloc_netdev);
@@ -2986,6 +2988,7 @@
#ifdef CONFIG_SYSFS
/* Compatiablity with error handling in drivers */
if (dev->reg_state == NETREG_UNINITIALIZED) {
+ bigref_destroy(&dev->netdev_refcnt);
kfree((char *)dev - dev->padded);
return;
}
@@ -2996,6 +2999,7 @@
/* will free via class release */
class_device_put(&dev->class_dev);
#else
+ bigref_destroy(&dev->netdev_refcnt);
kfree((char *)dev - dev->padded);
#endif
}
@@ -3210,7 +3214,7 @@
set_bit(__LINK_STATE_START, &queue->backlog_dev.state);
queue->backlog_dev.weight = weight_p;
queue->backlog_dev.poll = process_backlog;
- atomic_set(&queue->backlog_dev.refcnt, 1);
+ bigref_init(&queue->backlog_dev.netdev_refcnt);
}

dev_boot_phase = 0;
Index: alloc_percpu-2.6.13/net/core/net-sysfs.c
===================================================================
--- alloc_percpu-2.6.13.orig/net/core/net-sysfs.c 2005-08-28 16:41:01.000000000 -0700
+++ alloc_percpu-2.6.13/net/core/net-sysfs.c 2005-09-12 11:54:21.000000000 -0700
@@ -16,6 +16,7 @@
#include <net/sock.h>
#include <linux/rtnetlink.h>
#include <linux/wireless.h>
+#include <linux/bigref.h>

#define to_class_dev(obj) container_of(obj,struct class_device,kobj)
#define to_net_dev(class) container_of(class, struct net_device, class_dev)
@@ -400,6 +401,8 @@
= container_of(cd, struct net_device, class_dev);

BUG_ON(dev->reg_state != NETREG_RELEASED);
+
+ bigref_destroy(&dev->netdev_refcnt);

kfree((char *)dev - dev->padded);
}
-
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