On Tue, Apr 01, 2014 at 03:14:16PM +0300, Lori Jakab wrote:
> On 3/26/14, 2:16 AM, Ben Pfaff wrote:
> >On Mon, Mar 24, 2014 at 10:59:06AM -0700, Jarno Rajahalme wrote:
> >>This patch shrinks the struct ofpbuf from 104 to 48 bytes on 64-bit
> >>systems, or from 52 to 36 bytes on 32-bit systems (counting in the
> >>'l7' removal by the previous patch). This may help contribute to
> >>cache efficiency, and will speed up initializing, copying and
> >>manipulating ofpbufs. This is potentially important for the DPDK
> >>datapath, but the rest of the code base may also see a little benefit.
> >>
> >>Changes are:
> >>
> >>- Remove 'l7' pointer (previous patch).
> >>- Use offsets instead of layer pointers for l2_5, l3, and l4 using
> >> 'l2' as basis. Usually 'data' is the same as 'l2', but this is not
> >> always the case (e.g., when parsing or constructing a packet), so it
> >> can not be easily used as the offset basis. Also, packet parsing is
> >> faster if we do not need to maintain the offsets each time we pull
> >> data from the ofpbuf.
> >>- Use uint32_t for 'allocated' and 'size', as 2^32 is enough even for
> >> largest possible messages/packets.
> >>- Use packed enum for 'source'.
> >>- Rearrange to avoid unnecessary padding.
> >>- Remove 'private_p', which was used only in two cases, both of which
> >> had the invariant ('l2' == 'data'), so we can temporarily use 'l2'
> >> as a private pointer.
> >>
> >>Signed-off-by: Jarno Rajahalme <jrajaha...@nicira.com>
>
> Unfotunately I missed this patch until rebasing my layer 3 patch
> series [1] today.
>
> Before this patch, I set the 'l2' pointer to NULL and 'l3' to the
> start of the network header to represent a layer 3 packet in a
> struct ofpbuf. The way struct ofpbuf looks after this patch makes
> the assumption of always having layer 2 headers a lot stronger.
>
> I see two options for my patches going forward:
> 1) Add back 'l3' and remove 'l3_ofs' from struct ofpbuf (keeping the
> rest as is); or
> 2) Encode a layer 3 packet by setting 'l2' to the network header
> address and set l3_ofs to 0.
Can we do the following?
3) Replace 'l2' by 'l2_ofs' also?
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