On Tue, Apr 21, 2015 at 07:21:36PM +0100, Daniele Di Proietto wrote: > > > On 21 Apr 2015, at 17:01, Loftus, Ciara <ciara.lof...@intel.com> wrote: > > > > > > > >> -----Original Message----- > >> From: Ben Pfaff [mailto:b...@nicira.com] > >> Sent: Tuesday, April 21, 2015 4:08 PM > >> To: Loftus, Ciara > >> Cc: dev@openvswitch.org > >> Subject: Re: [ovs-dev] [PATCH RFC 0/1] dpif-netdev: Make EMC Size > >> Configurable > >> > >> On Tue, Apr 21, 2015 at 01:47:12PM +0100, Ciara Loftus wrote: > >>> This patch allows the user to specify the number of Exact Match Cache > >>> entries they wish to have available for their instance of the vswitch. > >>> This is a achieved by means of a 'configure' flag. > >>> > >>> At the moment, the default number of EMC entries is 1024, for which > >>> the switch should perform optimally up to this number of flows. > >>> However, if the user expects say roughly 2000 flows of traffic, an EMC > >>> with 2048 entries will perform better, allbeit with a larger demand on > >>> memory and time spent flushing the cache. If these requirements are > >>> acceptable to the user, they may choose to allocate 2048 entries like so, > >>> and in turn receive improved performance for their specific use case: > >>> > >>> './configure --with-emcsize=11' > >>> > >>> The number of entries is calculated as 2^11 = 2048. > >> > >> configure flags are really inconvenient. Is there a reason that this > >> can't be made configurable at runtime? It would be better yet if the > >> EMC size could automatically adjust itself. > > > > Thanks for the feedback. The implementation is naturally more complex for a > > runtime configurable but I think achievable - I'll look into it. > > Making it configurable at runtime is an option, but if that turns out > to be too complex I think we could just make it bigger. > > Each entry takes 176 bytes. We could, for example, reserve 16K > entries: that would take only 2.8 MB per core and (IMHO) it's > totally reasonable to reserve that memory in userspace. > > What do you guys think? > I'm CCing Ethan, as he might be interested in this too.
I'm happy to let you guys figure this out, I just think that configure-time options are undesirable in general. I'd probably make the same suggestion for any new configure option. _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev