On Tue, Jan 26, 2016 at 03:28:47AM +0000, Daniele Di Proietto wrote:
>
>
> On 25/01/2016 18:20, "Andy Zhou" <az...@ovn.org> wrote:
>
> >On Sun, Jan 24, 2016 at 8:32 AM, Ben Pfaff <b...@ovn.org> wrote:
> >
> >> Before this commit, emc_processing() copied a netdev_flow_key if there
> >>was
> >> no exact-match cache (EMC) hit. This commit eliminates the copy by
> >> constructing the netdev_flow_key in the place it would be copied.
> >>
> >> Found by inspection.
> >>
> >> Shahbaz (CCed) reports that this reduces the cost of an EMC miss by 72
> >> cycles in his test case in which the EMC is disabled. Presumably this
> >> is similarly valuable in cases where the EMC merely has few hits.
> >>
> >> CC: Muhammad Shahbaz <mshah...@cs.princeton.edu>
> >> Signed-off-by: Ben Pfaff <b...@ovn.org>
> >>
> >
> >Logic looks good to me.
> >
> >Acked-by: Andy Zhou <az...@ovn.org>
> >
> >I think Daniele is testing on performance impact on this patch. so it is
> >may be worthwhile
> >to wait for his input before pushing the change.
>
> If I disable the EMC I observe an increase in throughput when this patch
> is applied (from ~4.8 Mpps to ~5.4 Mpps).
>
> If the EMC is enabled, instead, I see a drop in throughput
> (from ~12.4 Mpps to ~12.0 Mpps) with this patch.
>
> At a first glance it looks like this patch is preventing my compiler
> (GCC 4.8) to perform some optimization.
Does the "restrict" keyword make any difference?
e.g. in the function prototype, changing
struct netdev_flow_key *keys
to
struct netdev_flow_key *restrict keys
Just a thought, not sure it'll help.
_______________________________________________
dev mailing list
dev@openvswitch.org
http://openvswitch.org/mailman/listinfo/dev
