28/03/2018 11:21, Burakov, Anatoly: > On 28-Mar-18 9:55 AM, Tan, Jianfeng wrote: > > On 3/28/2018 4:22 PM, Van Haaren, Harry wrote: > >> From: Thomas Monjalon [mailto:tho...@monjalon.net] > >>> 28/03/2018 04:08, Tan, Jianfeng: > >>>> From: Thomas Monjalon [mailto:tho...@monjalon.net] > >>>>> 27/03/2018 15:59, Anatoly Burakov: > >>>>>> Under the hood, we create a separate thread to deal with replies to > >>>>>> asynchronous requests, that will just wait to be notified by the > >>>>>> main thread, or woken up on a timer. > >>>>> > >>>>> I really don't like that a library is creating a thread. > >>>>> We don't even know where the thread is created (which core). > >>>>> Can it be a rte_service? or in the interrupt thread? > >>>> > >>>> Agree that we'd better not adding so many threads in a library. > >>>> > >>>> I was considering to merge all the threads into the interrupt thread, > >>> however, we don't have an interrupt thread in freebsd. Further, we don't > >>> implement alarm API in freebsd. That's why I tend to current > >>> implementation, > >>> and optimize it later. > >>> > >>> I would prefer we improve the current code now instead of polluting more > >>> with more uncontrolled threads. > >>> > >>>> For rte_service, it may be not a good idea to reply on it as it needs > >>> explicit API calls to setup. > >>> > >>> I don't see the issue of the explicit API. > >>> The IPC is a new service. > > > > My concern is that not every DPDK application sets up rte_service, but > > IPC will be used for very fundamental functions, like memory allocation. > > We could not possibly ask all DPDK applications to add rte_service now. > > > > And also take Harry's comments below into consideration, most likely, we > > will move these threads into interrupt thread now by adding > > > >> Although I do like to see new services, if we want to enable "core" > >> dpdk functionality with Services, we need a proper designed solution > >> for that. Service cores is not intended for "occasional" work - there > >> is no method to block and sleep on a specific service until work > >> becomes available, so this would imply a busy-polling. Using a service > >> (hence busy polling) for rte_malloc()-based memory mapping requests is > >> inefficient, and total overkill :) > >> > >> For this patch I suggest to use some blocking-read capable mechanism. > > > > The problem here is that we add too many threads; blocking-read does not > > decrease # of threads. > > > >> > >> The above said, in the longer term it would be good to have a design > >> that allows new file-descriptors to be added to a "dpdk core" thread, > >> which performs occasional lengthy work if the FD has data available. > > > > Interrupt thread vs rte_service, which is the direction to go? We > > actually have some others threads, in vhost and even virtio-user; we can > > also avoid those threads if we have a clear direction. > > > > Thanks, > > Jianfeng > > > > Hi all, > > First of all, @Thomas, this is not a "new library" - it's part of EAL.
I did not say it is a new library. > We're going to be removing a few threads from EAL as it is because of > IPC (Jianfeng has already submitted patches for those), I don't understand. Which threads are you going to remove? Which patch? > so i don't think > it's such a big deal to have two IPC threads instead of one. I'm open to > suggestions on how to make this work without a second thread, but i > don't see it. I am not against the second thread. I am against both threads :) > We've discussed possibility of using rte_service internally, but decided > against it for reasons already outlined by Harry - it's not a suitable > mechanism for this kind of thing, not as it is. > > Using interrupt thread for this _will_ work, however this will require a > a lot more changes, as currently alarm API allocates everything through > rte_malloc, while we want to use IPC for rte_malloc (which would make it > a circular dependency). So it'll probably be more API and more > complexity for dealing with malloc vs rte_malloc allocations. Hence the > least-bad approach taken here: a new thread. If everybody is happy enough with "least bad" design and not trying to improve the core design, what can I say?
