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net dst: use a percpu_counter to track entries

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struct dst_ops tracks number of allocated dst in an atomic_t field,
subject to high cache line contention in stress workload.

Switch to a percpu_counter, to reduce number of time we need to dirty a
central location. Place it on a separate cache line to avoid dirtying
read only fields.

Stress test :

(Sending 160.000.000 UDP frames,
IP route cache disabled, dual E5540 @2.53GHz,
32bit kernel, FIB_TRIE, SLUB/NUMA)

Before:

real    0m51.179s
user    0m15.329s
sys     10m15.942s

After:

real	0m45.570s
user	0m15.525s
sys	9m56.669s

With a small reordering of struct neighbour fields, subject of a
following patch, (to separate refcnt from other read mostly fields)

real	0m41.841s
user	0m15.261s
sys	8m45.949s

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2010-10-08 06:37:34 +00:00 • committed by David S. Miller
parent 0ed8ddf404
commit fc66f95c68
8 changed files with 100 additions and 35 deletions
Download patch file Download diff file Expand all files Collapse all files

4
net/ipv4/xfrm4_policy.c
View file

@ -174,7 +174,7 @@ static inline int xfrm4_garbage_collect(struct dst_ops *ops)
struct net *net = container_of(ops, struct net, xfrm.xfrm4_dst_ops);
xfrm4_policy_afinfo.garbage_collect(net);
return (atomic_read(&ops->entries) > ops->gc_thresh * 2);
return (dst_entries_get_slow(ops) > ops->gc_thresh * 2);
}
static void xfrm4_update_pmtu(struct dst_entry *dst, u32 mtu)
@ -232,7 +232,6 @@ static struct dst_ops xfrm4_dst_ops = {
.ifdown = xfrm4_dst_ifdown,
.local_out = __ip_local_out,
.gc_thresh = 1024,
.entries = ATOMIC_INIT(0),
};
static struct xfrm_policy_afinfo xfrm4_policy_afinfo = {
@ -288,6 +287,7 @@ void __init xfrm4_init(int rt_max_size)
* and start cleaning when were 1/2 full
*/
xfrm4_dst_ops.gc_thresh = rt_max_size/2;
dst_entries_init(&xfrm4_dst_ops);
xfrm4_state_init();
xfrm4_policy_init();