These functions compile to ~60 bytes of machine code each.
With this .config: http://busybox.net/~vda/kernel_config
there are 617 calls to netif_tx_stop_queue()
and 49 calls to netif_tx_stop_all_queues() in vmlinux.
Code size is reduced by 27 kbytes:
text data bss dec hex filename
82426986 22255416 20627456 125309858 77813a2 vmlinux.before
82399481 22255416 20627456 125282353 777a831 vmlinux
It may seem strange that a seemingly simple code like one in
netif_tx_stop_queue() compiles to ~60 bytes of code.
Well, it's true. Here's its disassembly:
netif_tx_stop_queue:
e8 b0 15 4d 00 callq <__fentry__>
48 85 ff test %rdi,%rdi
75 25 jne <netif_tx_stop_queue+0x2f>
55 push %rbp
be 7a 18 00 00 mov $0x187a,%esi
48 c7 c7 50 59 d8 85 mov $.rodata+0x1d85950,%rdi
48 89 e5 mov %rsp,%rbp
e8 54 5a 7d fd callq <warn_slowpath_null>
48 c7 c7 5f 59 d8 85 mov $.rodata+0x1d8595f,%rdi
31 c0 xor %eax,%eax
e8 b0 47 48 00 callq <printk>
eb 09 jmp <netif_tx_stop_queue+0x38>
f0 80 8f e0 01 00 00 01 lock orb $0x1,0x1e0(%rdi)
c3 retq
5d pop %rbp
c3 retq
This causes gcc to auto-deinline it before this patch, but with 203 separate
copies in each module which uses this function:
$ nm --size-sort vmlinux.before | grep -e ' netif_tx_stop_queue$' | wc -l
203
Signed-off-by: Denys Vlasenko <dvlas...@redhat.com>
CC: David S. Miller <da...@davemloft.net>
CC: Jiri Pirko <jpi...@redhat.com>
CC: linux-kernel@vger.kernel.org
CC: net...@vger.kernel.org
CC: netfilter-de...@vger.kernel.org
---
include/linux/netdevice.h | 19 ++-----------------
net/core/dev.c | 21 +++++++++++++++++++++
2 files changed, 23 insertions(+), 17 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index dcf6ec2..f650d16 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2546,14 +2546,7 @@ static inline void netif_tx_wake_all_queues(struct
net_device *dev)
}
}
-static inline void netif_tx_stop_queue(struct netdev_queue *dev_queue)
-{
- if (WARN_ON(!dev_queue)) {
- pr_info("netif_stop_queue() cannot be called before
register_netdev()\n");
- return;
- }
- set_bit(__QUEUE_STATE_DRV_XOFF, &dev_queue->state);
-}
+void netif_tx_stop_queue(struct netdev_queue *dev_queue);
/**
* netif_stop_queue - stop transmitted packets
@@ -2567,15 +2560,7 @@ static inline void netif_stop_queue(struct net_device
*dev)
netif_tx_stop_queue(netdev_get_tx_queue(dev, 0));
}
-static inline void netif_tx_stop_all_queues(struct net_device *dev)
-{
- unsigned int i;
-
- for (i = 0; i < dev->num_tx_queues; i++) {
- struct netdev_queue *txq = netdev_get_tx_queue(dev, i);
- netif_tx_stop_queue(txq);
- }
-}
+void netif_tx_stop_all_queues(struct net_device *dev);
static inline bool netif_tx_queue_stopped(const struct netdev_queue *dev_queue)
{
diff --git a/net/core/dev.c b/net/core/dev.c
index 962ee9d..569031f 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6261,6 +6261,27 @@ static int netif_alloc_netdev_queues(struct net_device
*dev)
return 0;
}
+void netif_tx_stop_queue(struct netdev_queue *dev_queue)
+{
+ if (WARN_ON(!dev_queue)) {
+ pr_info("netif_stop_queue() cannot be called before
register_netdev()\n");
+ return;
+ }
+ set_bit(__QUEUE_STATE_DRV_XOFF, &dev_queue->state);
+}
+EXPORT_SYMBOL(netif_tx_stop_queue);
+
+void netif_tx_stop_all_queues(struct net_device *dev)
+{
+ unsigned int i;
+
+ for (i = 0; i < dev->num_tx_queues; i++) {
+ struct netdev_queue *txq = netdev_get_tx_queue(dev, i);
+ netif_tx_stop_queue(txq);
+ }
+}
+EXPORT_SYMBOL(netif_tx_stop_all_queues);
+
/**
* register_netdevice - register a network device
* @dev: device to register
--
1.8.1.4
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