Re: [PATCH 2/2 net-next] openvswitch: Use skb_zerocopy() for upcall

On 11/08/2013 11:47 AM, Thomas Graf wrote:

Use of skb_zerocopy() avoids the expensive call to memcpy() when
copying the packet data into the Netlink skb. Completes checksum
through skb_checksum_help() if needed.

Netlink messaged must be properly padded and aligned to meet
sanity checks of the user space counterpart.

Cost of memcpy is significantly reduced from:
+   7.48%       vhost-8471  [k] memcpy
+   5.57%     ovs-vswitchd  [k] memcpy
+   2.81%       vhost-8471  [k] csum_partial_copy_generic

to:
+   5.72%     ovs-vswitchd  [k] memcpy
+   3.32%       vhost-5153  [k] memcpy
+   0.68%       vhost-5153  [k] skb_zerocopy

(megaflows disabled)

Signed-off-by: Thomas Graf <tgraf-G/eBtMaohhA@public.gmane.org>
Cc: Jesse Gross <redacted>
Cc: Eric Dumazet <redacted>

Reviewed-by: Daniel Borkmann <redacted>