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| author | Eric Dumazet <eric.dumazet@gmail.com> | 2010-10-11 10:22:12 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2010-10-12 12:35:25 -0700 |
| commit | 29b4433d991c88d86ca48a4c1cc33c671475be4b (patch) | |
| tree | 2ad21b86aab8193c4533820c40cd31af97a7377f /include | |
| parent | f0b9f4725180ea58c8da78b3de0b4e0ad180fc2c (diff) | |
| download | linux-29b4433d991c88d86ca48a4c1cc33c671475be4b.tar.gz linux-29b4433d991c88d86ca48a4c1cc33c671475be4b.tar.bz2 linux-29b4433d991c88d86ca48a4c1cc33c671475be4b.zip | |
net: percpu net_device refcount
We tried very hard to remove all possible dev_hold()/dev_put() pairs in
network stack, using RCU conversions.
There is still an unavoidable device refcount change for every dst we
create/destroy, and this can slow down some workloads (routers or some
app servers, mmap af_packet)
We can switch to a percpu refcount implementation, now dynamic per_cpu
infrastructure is mature. On a 64 cpus machine, this consumes 256 bytes
per device.
On x86, dev_hold(dev) code :
before
lock incl 0x280(%ebx)
after:
movl 0x260(%ebx),%eax
incl fs:(%eax)
Stress bench :
(Sending 160.000.000 UDP frames,
IP route cache disabled, dual E5540 @2.53GHz,
32bit kernel, FIB_TRIE)
Before:
real 1m1.662s
user 0m14.373s
sys 12m55.960s
After:
real 0m51.179s
user 0m15.329s
sys 10m15.942s
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/netdevice.h | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 4160db3721ba..14fbb04c459d 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -1026,7 +1026,7 @@ struct net_device { struct timer_list watchdog_timer; /* Number of references to this device */ - atomic_t refcnt ____cacheline_aligned_in_smp; + int __percpu *pcpu_refcnt; /* delayed register/unregister */ struct list_head todo_list; @@ -1330,6 +1330,7 @@ static inline void unregister_netdevice(struct net_device *dev) unregister_netdevice_queue(dev, NULL); } +extern int netdev_refcnt_read(const struct net_device *dev); extern void free_netdev(struct net_device *dev); extern void synchronize_net(void); extern int register_netdevice_notifier(struct notifier_block *nb); @@ -1798,7 +1799,7 @@ extern void netdev_run_todo(void); */ static inline void dev_put(struct net_device *dev) { - atomic_dec(&dev->refcnt); + irqsafe_cpu_dec(*dev->pcpu_refcnt); } /** @@ -1809,7 +1810,7 @@ static inline void dev_put(struct net_device *dev) */ static inline void dev_hold(struct net_device *dev) { - atomic_inc(&dev->refcnt); + irqsafe_cpu_inc(*dev->pcpu_refcnt); } /* Carrier loss detection, dial on demand. The functions netif_carrier_on |