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| author | Eric Dumazet <edumazet@google.com> | 2016-04-26 15:30:07 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2016-04-27 21:55:45 -0400 |
| commit | 501e7ef569f4ea2dc7e50773cf6a5d757c94f9b4 (patch) | |
| tree | ed5b66685cc0b9623945a1b99066502d15fa19f3 /include/linux/netdevice.h | |
| parent | 35ef7d689d7d54ab345b179e50c749fe3a2529eb (diff) | |
| download | op-kernel-dev-501e7ef569f4ea2dc7e50773cf6a5d757c94f9b4.zip op-kernel-dev-501e7ef569f4ea2dc7e50773cf6a5d757c94f9b4.tar.gz | |
net-rfs: fix false sharing accessing sd->input_queue_head
sd->input_queue_head is incremented for each processed packet
in process_backlog(), and read from other cpus performing
Out Of Order avoidance in get_rps_cpu()
Moving this field in a separate cache line keeps it mostly
hot for the cpu in process_backlog(), as other cpus will
only read it.
In a stress test, process_backlog() was consuming 6.80 % of cpu cycles,
and the patch reduced the cost to 0.65 %
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux/netdevice.h')
| -rw-r--r-- | include/linux/netdevice.h | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 18d8394..934ca86 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -2747,11 +2747,15 @@ struct softnet_data { struct sk_buff *completion_queue; #ifdef CONFIG_RPS - /* Elements below can be accessed between CPUs for RPS */ + /* input_queue_head should be written by cpu owning this struct, + * and only read by other cpus. Worth using a cache line. + */ + unsigned int input_queue_head ____cacheline_aligned_in_smp; + + /* Elements below can be accessed between CPUs for RPS/RFS */ struct call_single_data csd ____cacheline_aligned_in_smp; struct softnet_data *rps_ipi_next; unsigned int cpu; - unsigned int input_queue_head; unsigned int input_queue_tail; #endif unsigned int dropped; |
