packet: reorder a member in packet_ring_buffer
There's a 4 byte hole in packet_ring_buffer structure before
prb_bdqc, that can be filled with 'pending' member, thus we can
reduce the overall structure size from 224 bytes to 216 bytes.
This also has the side-effect, that in struct packet_sock 2*4 byte
holes after the embedded packet_ring_buffer members are removed,
and overall, packet_sock can be reduced by 1 cacheline:
Before: size: 1344, cachelines: 21, members: 24
After: size: 1280, cachelines: 20, members: 24
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/packet/internal.h b/net/packet/internal.h
index e891f02..650751b 100644
--- a/net/packet/internal.h
+++ b/net/packet/internal.h
@@ -54,6 +54,7 @@
struct packet_ring_buffer {
struct pgv *pg_vec;
+
unsigned int head;
unsigned int frames_per_block;
unsigned int frame_size;
@@ -63,8 +64,9 @@
unsigned int pg_vec_pages;
unsigned int pg_vec_len;
- struct tpacket_kbdq_core prb_bdqc;
atomic_t pending;
+
+ struct tpacket_kbdq_core prb_bdqc;
};
extern struct mutex fanout_mutex;