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authorEric Dumazet <edumazet@google.com>2016-04-26 15:30:07 -0700
committerDavid S. Miller <davem@davemloft.net>2016-04-27 21:55:45 -0400
commit501e7ef569f4ea2dc7e50773cf6a5d757c94f9b4 (patch)
treeed5b66685cc0b9623945a1b99066502d15fa19f3 /include/linux/netdevice.h
parent35ef7d689d7d54ab345b179e50c749fe3a2529eb (diff)
downloadop-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.h8
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;
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