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ipv4: percpu nh_rth_output cache

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Input path is mostly run under RCU and doesnt touch dst refcnt

But output path on forwarding or UDP workloads hits
badly dst refcount, and we have lot of false sharing, for example
in ipv4_mtu() when reading rt->rt_pmtu

Using a percpu cache for nh_rth_output gives a nice performance
increase at a small cost.

24 udpflood test on my 24 cpu machine (dummy0 output device)
(each process sends 1.000.000 udp frames, 24 processes are started)

before : 5.24 s
after : 2.06 s
For reference, time on linux-3.5 : 6.60 s

Signed-off-by: Eric Dumazet <edumazet@google.com>
Tested-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2012-07-31 05:45:30 +00:00 • committed by David S. Miller
parent 54764bb647
commit d26b3a7c4b
3 changed files with 34 additions and 7 deletions
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3
include/net/ip_fib.h
View file

@ -21,6 +21,7 @@
#include <linux/rcupdate.h>
#include <net/fib_rules.h>
#include <net/inetpeer.h>
#include <linux/percpu.h>
struct fib_config {
u8 fc_dst_len;
@ -81,7 +82,7 @@ struct fib_nh {
__be32 nh_gw;
__be32 nh_saddr;
int nh_saddr_genid;
struct rtable __rcu *nh_rth_output;
struct rtable __rcu * __percpu *nh_pcpu_rth_output;
struct rtable __rcu *nh_rth_input;
struct fnhe_hash_bucket *nh_exceptions;
};