On Thu, Jan 28, 2016 at 01:14:59AM +0000, Daniele Di Proietto wrote: > > > On 26/01/2016 08:23, "Ben Pfaff" <b...@ovn.org> wrote: > > >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. > > I tried adding "restrict", but I didn't notice any differences. > > It seems that GCC decides to inline a different set of functions with > this patch applied. > > Given the numbers, and given that we can restore the performance of the > emc path in other ways, I'm in favour of this patch. > > Acked-by: Daniele Di Proietto <diproiet...@vmware.com>
Thanks. I applied this to master. _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
