path: root/drivers/net/ethernet/intel/ixgb
diff options
authorEric Dumazet <eric.dumazet@gmail.com>2011-11-14 06:05:34 +0000
committerDavid S. Miller <davem@davemloft.net>2011-11-14 14:13:30 -0500
commite52fcb2462ac484e6dd6e68869536609f0216938 (patch)
tree794407ff242481d5d09e3e669cabfe129d80f6df /drivers/net/ethernet/intel/ixgb
parentb2b5ce9d1ccf1c45f8ac68e5d901112ab76ba199 (diff)
bnx2x: uses build_skb() in receive path
bnx2x uses following formula to compute its rx_buf_sz : dev->mtu + 2*L1_CACHE_BYTES + 14 + 8 + 8 + 2 Then core network adds NET_SKB_PAD and SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) Final allocated size for skb head on x86_64 (L1_CACHE_BYTES = 64, MTU=1500) : 2112 bytes : SLUB/SLAB round this to 4096 bytes. Since skb truesize is then bigger than SK_MEM_QUANTUM, we have lot of false sharing because of mem_reclaim in UDP stack. One possible way to half truesize is to reduce the need by 64 bytes (2112 -> 2048 bytes) Instead of allocating a full cache line at the end of packet for alignment, we can use the fact that skb_shared_info sits at the end of skb->head, and we can use this room, if we convert bnx2x to new build_skb() infrastructure. skb_shared_info will be initialized after hardware finished its transfert, so we can eventually overwrite the final padding. Using build_skb() also reduces cache line misses in the driver, since we use cache hot skb instead of cold ones. Number of in-flight sk_buff structures is lower, they are recycled while still hot. Performance results : (820.000 pps on a rx UDP monothread benchmark, instead of 720.000 pps) Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> CC: Eilon Greenstein <eilong@broadcom.com> CC: Ben Hutchings <bhutchings@solarflare.com> CC: Tom Herbert <therbert@google.com> CC: Jamal Hadi Salim <hadi@mojatatu.com> CC: Stephen Hemminger <shemminger@vyatta.com> CC: Thomas Graf <tgraf@infradead.org> CC: Herbert Xu <herbert@gondor.apana.org.au> CC: Jeff Kirsher <jeffrey.t.kirsher@intel.com> Acked-by: Eilon Greenstein <eilong@broadcom.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/ethernet/intel/ixgb')
0 files changed, 0 insertions, 0 deletions