> -----Original Message----- > From: David Marchand <[email protected]> > Sent: Wednesday, June 24, 2020 10:24 AM > To: Ananyev, Konstantin <[email protected]> > Cc: [email protected]; [email protected]; Richardson, Bruce > <[email protected]>; [email protected]; [email protected]; > Stokes, Ian <[email protected]>; [email protected]; Thomas Monjalon > <[email protected]>; Mcnamara, John > <[email protected]>; Kovacevic, Marko <[email protected]>; > Burakov, Anatoly <[email protected]>; Olivier > Matz <[email protected]>; Andrew Rybchenko <[email protected]>; > Neil Horman <[email protected]> > Subject: Re: [dpdk-dev] [PATCH v3 6/9] eal: register non-EAL threads as lcores > > On Tue, Jun 23, 2020 at 3:16 PM Ananyev, Konstantin > <[email protected]> wrote: > > > Even before this series, MP has no protection on lcore placing between > > > primary and secondary processes. > > > > Agree, it is not a new problem, it has been there for a while. > > Though making lcore assignment dynamic will make it more noticeable and > > harder to avoid. > > With static only lcore distribution it is much easier to control things. > > > > > Personally, I have no use for DPDK MP and marking MP as not supporting > > > this new feature is tempting for a first phase. > > > If this is a strong requirement, I can look at it in a second phase. > > > What do you think? > > > > In theory it is possible to mark this new API as not supported for MP. > > At least for now. Though I think it is sort of temporal solution. > > AFAIK, MP is used by customers, so sooner or later someone will hit that > > problem. > > I understand this argument. > But then we don't see those customers giving feedback. > > > > Let say, we do have pdump app/library in our mainline. > > As I can see - it will be affected when users will start using this new > > dynamic lcore API > > inside their apps. > > Supporting lcore allocation in MP requires exchanges between > primary/secondary processes like what we have for memory allocations. > It will be quite a beast to get to work fine, while not even knowing > if people actually want to use both.
I don't think we need to re-implement RPC as we did for memory subsystem. One relatively simple approach - move lcore_role[] and related lock into shared memory (separate memzone or so). I think it should help a lot and will solve majority of the problems. One limitation - init/fini callbacks can be static only. As the drawback, it will introduce change in current behaviour: secondary process with lcore-mask that intersects with master lcore-mask will fail to start. Second approach - make lcore_id local process entity: prohibit indexing by lcore_id in shared data structures. Let say for mempool - make cache local (per process). While that approach is probably more elegant and consistent, it would require more work and will cause ABI (maybe API also) breakage. > For v4, I added a check to exclude MP and the new API. Do you mean - make this new dynamic-lcore API return an error if callied from secondary process? > I am still willing to help if people do care about using both features > together.
