> -----Original Message----- > From: Ajit Khaparde <[email protected]> > Sent: Wednesday, October 28, 2020 5:02 PM > To: Ma, Liang J <[email protected]> > Cc: Jerin Jacob <[email protected]>; Ananyev, Konstantin > <[email protected]>; Thomas Monjalon > <[email protected]>; dpdk-dev <[email protected]>; Ruifeng Wang (Arm Technology > China) <[email protected]>; Wang, Haiyue > <[email protected]>; Richardson, Bruce <[email protected]>; > Hunt, David <[email protected]>; Neil Horman > <[email protected]>; McDaniel, Timothy <[email protected]>; > Eads, Gage <[email protected]>; Marcin Wojtas > <[email protected]>; Guy Tzalik <[email protected]>; Harman Kalra > <[email protected]>; John Daley <[email protected]>; Wei > Hu (Xavier <[email protected]>; Ziyang Xuan <[email protected]>; > [email protected]; Yong Wang > <[email protected]>; [email protected] > Subject: Re: [PATCH v10 0/9] Add PMD power mgmt > > On Wed, Oct 28, 2020 at 9:47 AM Liang, Ma <[email protected]> wrote: > > > > On 28 Oct 21:27, Jerin Jacob wrote: > > > On Wed, Oct 28, 2020 at 9:19 PM Ananyev, Konstantin > > > <[email protected]> wrote: > > > > > > > > > 28/10/2020 14:49, Jerin Jacob: > > > > > > > > > > On Wed, Oct 28, 2020 at 7:05 PM Liang, Ma > > > > > > > > > > <[email protected]> wrote: > > > > > > > > > > > > > > > > > > > > > > Hi Thomas, > > > > > > > > > > > I think I addressed all of the questions in relation to > > > > > > > > > > > V9. I don't think I can solve the issue of a generic API > > > > > > > > > > > on my own. > From the > > > > > > > > > Community Call last week Jerin also said that a generic was > > > > > > > > > investigated but that a single solution wasn't feasible. > > > > > > > > > > > > > > > > > > > > I think, From the architecture point of view, the specific > > > > > > > > > > functionally of UMONITOR may not be abstracted. > > > > > > > > > > But from the ethdev callback point of view, Can it be > > > > > > > > > > abstracted in > > > > > > > > > > such a way that packet notification available through > > > > > > > > > > checking interrupt status register or ring descriptor > > > > > > > > > > location, etc by > > > > > > > > > > the driver. Use that callback as a notification mechanism > > > > > > > > > > rather > > > > > > > > > > than defining a memory-based scheme that UMONITOR expects? > > > > > > > > > > or similar > > > > > > > > > > thoughts on abstraction. > > > > > > > > > > > > > > > > I think there is probably some sort of misunderstanding. > > > > > > > > This API is not about providing acync notification when next > > > > > > > > packet arrives. > > > > > > > > This is about to putting core to sleep till some event (or > > > > > > > > timeout) happens. > > > > > > > > From my perspective the closest analogy: cond_timedwait(). > > > > > > > > So we need PMD to tell us what will be the address of the > > > > > > > > condition variable > > > > > > > > we should sleep on. > > > > > > > > > > > > > > > > > I agree with Jerin. > > > > > > > > > The ethdev API is the blocking problem. > > > > > > > > > First problem: it is not well explained in doxygen. > > > > > > > > > Second problem: it is probably not generic enough (if we > > > > > > > > > understand it well) > > > > > > > > > > > > > > > > It is an address to sleep(/wakeup) on, plus expected value. > > > > > > > > Honestly, I can't think-up of anything even more generic then > > > > > > > > that. > > > > > > > > If you guys have something particular in mind - please share. > > > > > > > > > > > > > > Current PMD callback: > > > > > > > typedef int (*eth_get_wake_addr_t)(void *rxq, volatile void > > > > > > > **tail_desc_addr, + uint64_t *expected, uint64_t *mask, uint8_t > > > > > > > *data_sz); > > > > > > > > > > > > > > Can we make it as > > > > > > > typedef void (*core_sleep_t)(void *rxq) > > > > > > > > > > > > > > if we do such abstraction and "move the polling on memory by > > > > > > > HW/CPU" > > > > > > > to the driver using a helper function then > > > > > > > I can think of abstracting in some way in all PMDs. > > > > > > > > > > > > Ok I see, thanks for explanation. > > > > > > From my perspective main disadvantage of such approach - > > > > > > it can't be extended easily. > > > > > > If/when will have an ability for core to sleep/wake-up on multiple > > > > > > events > > > > > > (multiple addresses) will have to either rework that API again. > > > > > > > > > > I think, we can enumerate the policies and pass the associated > > > > > structures as input to the driver. > > > > > > > > What I am trying to say: with that API we will not be able to wait > > > > for events from multiple devices (HW queues). > > > > I.E. something like that: > > > > > > > > get_wake_addr(port=X, ..., &addr[0], ...); > > > > get_wake_addr(port=Y,..., &addr[1],...); > > > > wait_on_multi(addr, 2); > > > > > > > > wouldn't be possible. > > > > > > I see. But the current implementation dictates the only queue bound to > > > a core. Right? > > Current implementation only support 1:1 queue/core mapping is because of > > the limitation of umwait/umonitor which can not work with multiple address > > range. However, for other scheme like PASUE/Freq Scale have no such > > limitation. > > The proposed API itself doesn't limit the 1:1 queue/core mapping. > > The PMD would not know if it is 1:1 queue/core or any other shared scheme. > So the intelligence and decision making is best left to the application. > I think PMD and the underlying hardware does not need to know what kind of > power management scheme is implemented.
Yep, good point. 100% agree. > IMHO the original API which provides the address, value and mask should > suffice. > Any other callback or handshake between PMD and application may be an > overkill. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Note: core_sleep_t can take some more arguments such as enumerated > > > > > > > policy if something more needs to be pushed to the driver. > > > > > > > > > > > > > > Thoughts? > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > This API is experimental and other vendor support can be > > > > > > > > > > > added as needed. If there are any other open issue let me > > > > > > > > > > > know? > > > > > > > > > > > > > > > > > > Being experimental is not an excuse to throw something > > > > > > > > > which is not satisfying. > > > > > > > > > > > > > > > > > > > > > > > > > >
