> -----Original Message----- > From: Burakov, Anatoly <anatoly.bura...@intel.com> > Sent: Wednesday, February 17, 2021 12:09 PM > To: Van Haaren, Harry <harry.van.haa...@intel.com>; Richardson, Bruce > <bruce.richard...@intel.com> > Cc: dev@dpdk.org > Subject: Re: [dpdk-dev] [PATCH] eal: support using 0 as coremask for no- > affinitization > > On 16-Feb-21 5:44 PM, Van Haaren, Harry wrote: > >> -----Original Message----- > >> From: Bruce Richardson <bruce.richard...@intel.com> > >> Sent: Tuesday, February 16, 2021 5:31 PM > >> To: Van Haaren, Harry <harry.van.haa...@intel.com> > >> Cc: Burakov, Anatoly <anatoly.bura...@intel.com>; dev@dpdk.org > >> Subject: Re: [dpdk-dev] [PATCH] eal: support using 0 as coremask for no- > >> affinitization > >> > >> On Tue, Feb 16, 2021 at 05:22:25PM +0000, Van Haaren, Harry wrote: > >>>> -----Original Message----- > >>>> From: Burakov, Anatoly <anatoly.bura...@intel.com> > >>>> Sent: Tuesday, February 16, 2021 10:53 AM > >>>> To: Richardson, Bruce <bruce.richard...@intel.com>; Van Haaren, Harry > >>>> <harry.van.haa...@intel.com> > >>>> Cc: dev@dpdk.org > >>>> Subject: Re: [dpdk-dev] [PATCH] eal: support using 0 as coremask for no- > >>>> affinitization > >>>> > >>>> On 16-Feb-21 10:46 AM, Bruce Richardson wrote: > >>>>> On Tue, Feb 16, 2021 at 10:36:13AM +0000, Burakov, Anatoly wrote: > >>>>>> On 16-Feb-21 9:43 AM, Bruce Richardson wrote: > >>>>>>> Allow the user to specify that they don't want any core pinning from > >> DPDK > >>>>>>> by passing in the coremask of 0. > >>>>>>> --- > >>>>>> > >>>>>> I haven't checked what happens yet, but down the line we also set > affinity > >>>>>> for service cores as well as interrupt thread. what would be the > semantics > >>>>>> of those in this particular case? do we want the same ability for > >>>>>> service > >>>>>> cores (i.e. pick a non-affinitized core)? And where does interrupt > >>>>>> thread > >>>>>> affinitize in this case (presumably, nowhere too)? > >>>>>> > >>>>> I have not checked the service core setup, because a) I forgot about > >>>>> them > >>>>> and b) I'm not sure how their affinity rules work with respect to the > >>>>> main > >>>>> lcore mask. On the other hand I did check out that the lcore mask for > >>>>> all > >>>>> non-pinned threads, or control threads, is the full set of bits as > >>>>> expected. > >>>>> > >>>>> /Bruce > >>>>> > >>>> > >>>> +Harry, > >>>> > >>>> I believe service core mask must not overlap with lcore masks, so > >>>> presumably using 0 as lcore mask would make it so that any service core > >>>> mask will be valid (which is presumably what we want?). > >>> > >>> Services cores -S list or -s <mask> *must* overlap with the RTE lcores, > >>> EAL > >>> then"steals" the service cores from the application lcores, code that > >> implements here: > >>> http://git.dpdk.org/dpdk- > >> stable/tree/lib/librte_eal/common/eal_common_options.c?h=20.11#n657 > >>> > >>>> Should service cores also have a "just pick a core" parameter? > >>> > >>> I'm not sure, depends on what the bigger goal is here. > >>> Assuming we're enabling this for ROLE_RTE threads, then > >>> it would seem to me that ROLE_SERVICE and control threads > >>> would require similar treatment? > >>> > >> Control threads are affinitised to all cores not in the coremask, which > >> means in this case that they can run anywhere on the system the OS chooses. > > > > Ah ok, fair enough yes. > > > >> In case of service cores, it would seem that using service cores with an > >> empty coremask is just not compatible. I would assume that this > >> incompatibility already exists when one has a coremask with only one core > >> already in it. > > > > Yes, correct, it would leave zero lcores for ROLE_RTE, meaning no lcores > > for the > application. > > A possible solution would be to special case a zero service core mask and > > apply > the same > > treatment as ROLE_RTE coremask? > > > > Others likely have better ideas - I don't have time to follow DPDK > threading/pinning topic > > closely at the moment. > > > > I don't think it's a good idea to disallow service cores functionality > in this case, but i don't have a way to solve this, other than > implementing similar 0x0 coremask for service cores and assume it always > means "one core affinitized to wherever the OS feels like it". After > all, with lcore mask 0x0 we assume user wants one single core only, so > following that, one single service core is a valid extrapolation IMO.
OK with me - seems reasonable. > Perhaps specifying the number of l/s cores when using 0x0 would be > interesting, but IMO unless there's ask for it, i'd rather not > overcomplicate things and go with similar semantics for service cores, > and just allow a 0x0 coremask that means only one unaffinitized service > core will be created. > > Thoughts? Agree with keeping-it-simple if possible, and agree that unaffinitized with a single service-core with a 0x0 mask makes sense. Most important to me is to maintain backward compatibility with existing usage of -S and -s, but this shouldn't break anything? (Famous last words..) > -- > Thanks, > Anatoly
