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ixgbe: Reduce Rx header size to what is actually used 

The recent changes to netdev_alloc_skb actually make it so that the size of
the buffer now actually has a more direct input on the truesize.  So in
order to make best use of the piece of a page we are allocated I am
reducing the IXGBE_RX_HDR_SIZE to 256 so that our truesize will be reduced
by 256 bytes as well.

This should result in performance improvements since the number of uses per
page should increase from 4 to 6 in the case of a 4K page.  In addition we
should see socket performance improvements due to the truesize dropping
to less than 1K for buffers less than 256 bytes.

Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
This commit is contained in:
Alexander Duyck 2012-05-24 01:59:27 +00:00 committed by Jeff Kirsher
parent ce42260669
commit 252562c207
2 changed files with 10 additions and 9 deletions
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15
drivers/net/ethernet/intel/ixgbe/ixgbe.h
View File

@ -77,17 +77,18 @@
#define IXGBE_MAX_FCPAUSE 0xFFFF
/* Supported Rx Buffer Sizes */
#define IXGBE_RXBUFFER_512 512 /* Used for packet split */
#define IXGBE_RXBUFFER_256 256 /* Used for skb receive header */
#define IXGBE_MAX_RXBUFFER 16384 /* largest size for a single descriptor */
/*
* NOTE: netdev_alloc_skb reserves up to 64 bytes, NET_IP_ALIGN mans we
* reserve 2 more, and skb_shared_info adds an additional 384 bytes more,
* this adds up to 512 bytes of extra data meaning the smallest allocation
* we could have is 1K.
* i.e. RXBUFFER_512 --> size-1024 slab
* NOTE: netdev_alloc_skb reserves up to 64 bytes, NET_IP_ALIGN means we
* reserve 64 more, and skb_shared_info adds an additional 320 bytes more,
* this adds up to 448 bytes of extra data.
*
* Since netdev_alloc_skb now allocates a page fragment we can use a value
* of 256 and the resultant skb will have a truesize of 960 or less.
*/
#define IXGBE_RX_HDR_SIZE IXGBE_RXBUFFER_512
#define IXGBE_RX_HDR_SIZE IXGBE_RXBUFFER_256
#define MAXIMUM_ETHERNET_VLAN_SIZE (ETH_FRAME_LEN + ETH_FCS_LEN + VLAN_HLEN)

4
drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
View File

@ -1517,8 +1517,8 @@ static bool ixgbe_cleanup_headers(struct ixgbe_ring *rx_ring,
* 60 bytes if the skb->len is less than 60 for skb_pad.
*/
pull_len = skb_frag_size(frag);
if (pull_len > 256)
pull_len = ixgbe_get_headlen(va, pull_len);
if (pull_len > IXGBE_RX_HDR_SIZE)
pull_len = ixgbe_get_headlen(va, IXGBE_RX_HDR_SIZE);
/* align pull length to size of long to optimize memcpy performance */
skb_copy_to_linear_data(skb, va, ALIGN(pull_len, sizeof(long)));