Eric Lee / linux-smarc-t335x-v3.2

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Commit 8bdd663aba341c15cd2fa9dbd7061b8b387964dc

Authored by Eric Dumazet
Committed by David S. Miller
1 parent ff4fbd43fe
Exists in master and in 4 other branches v3.2_AM335xPSP_04.06.00.11, v3.2_NEWT335xPSP_04.06.00.11, v3.2_SBC_SMARTMEN, v3.2_SMARCT335xPSP_04.06.00.11

net: reorder fields of struct socket 

On x86_64, its rather unfortunate that "wait_queue_head_t wait"
field of "struct socket" spans two cache lines (assuming a 64
bytes cache line in current cpus)

offsetof(struct socket, wait)=0x30
sizeof(wait_queue_head_t)=0x18

This might explain why Kenny Chang noticed that his multicast workload
was performing bad with 64 bit kernels, since more cache lines ping pongs
were involved.

This litle patch moves "wait" field next "fasync_list" so that both
fields share a single cache line, to speedup sock_def_readable()

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Showing 1 changed file with 6 additions and 2 deletions Side-by-side Diff

... ... @@ -129,11 +129,15 @@
129 129 socket_state state;
130 130 short type;
131 131 unsigned long flags;
132   - const struct proto_ops *ops;
  132 + /*
  133 + * Please keep fasync_list & wait fields in the same cache line
  134 + */
133 135 struct fasync_struct *fasync_list;
  136 + wait_queue_head_t wait;
  137 +
134 138 struct file *file;
135 139 struct sock *sk;
136   - wait_queue_head_t wait;
  140 + const struct proto_ops *ops;
137 141 };
138 142  
139 143 struct vm_area_struct;