09/10/2020 11:25, Burakov, Anatoly: > On 09-Oct-20 6:42 AM, Jerin Jacob wrote: > > On Thu, Oct 8, 2020 at 10:38 PM Ananyev, Konstantin > > <konstantin.anan...@intel.com> wrote: > >> > >>> > >>> On Thu, Oct 8, 2020 at 6:57 PM Burakov, Anatoly > >>> <anatoly.bura...@intel.com> wrote: > >>>> > >>>> On 08-Oct-20 9:44 AM, Jerin Jacob wrote: > >>>>> On Thu, Oct 8, 2020 at 2:04 PM Thomas Monjalon <tho...@monjalon.net> > >>>>> wrote: > >>>>>> > >>>>>>> Add two new power management intrinsics, and provide an implementation > >>>>>>> in eal/x86 based on UMONITOR/UMWAIT instructions. The instructions > >>>>>>> are implemented as raw byte opcodes because there is not yet > >>>>>>> widespread > >>>>>>> compiler support for these instructions. > >>>>>>> > >>>>>>> The power management instructions provide an architecture-specific > >>>>>>> function to either wait until a specified TSC timestamp is reached, or > >>>>>>> optionally wait until either a TSC timestamp is reached or a memory > >>>>>>> location is written to. The monitor function also provides an optional > >>>>>>> comparison, to avoid sleeping when the expected write has already > >>>>>>> happened, and no more writes are expected. > >>>>>>> > >>>>>>> For more details, Please reference Intel SDM Volume 2. > >>>>>> > >>>>>> I really would like to see feedbacks from other arch maintainers. > >>>>>> Unfortunately they were not Cc'ed. > >>>>> > >>>>> Shared the feedback from the arm64 perspective here. Yet to get a reply > >>>>> on this. > >>>>> http://mails.dpdk.org/archives/dev/2020-September/181646.html > >>>>> > >>>>>> Also please mark the new functions as experimental. > >>>>>> > >>>>>> > >>>> > >>>> Hi Jerin, > >>> > >>> Hi Anatoly, > >>> > >>>> > >>>> > IMO, We must introduce some arch feature-capability _get_ scheme to > >>>> tell > >>>> > the consumer of this API is only supported on x86. Probably as > >>>> functions[1] > >>>> > or macro flags scheme and have a stub for the other architectures as > >>>> the > >>>> > API marked as generic ie rte_power_* not rte_x86_.. > >>>> > > >>>> > This will help the consumer to create workers based on the > >>>> instruction features > >>>> > which can NOT be abstracted as a generic feature across the > >>>> architectures. > >>>> > >>>> I'm not entirely sure what you mean by that. > >>>> > >>>> I mean, yes, we should have added stubs for other architectures, and we > >>>> will add those in future revisions, but what does your proposed runtime > >>>> check accomplish that cannot currently be done with CPUID flags? > >>> > >>> > >>> RTE_CPUFLAG_WAITPKG flag definition is not available in other > >>> architectures. > >>> i.e RTE_CPUFLAG_WAITPKG defined in > >>> lib/librte_eal/x86/include/rte_cpuflags.h > >>> and it is used in http://patches.dpdk.org/patch/79540/ as generic API. > >>> I doubt http://patches.dpdk.org/patch/79540/ would compile on non-x86. > >> > >> > >> I am agree with Jerin, that we need some generic way to > >> figure-out does platform supports power_monitor() or not. > >> Though not sure do we need to create a new feature-get framework here... > > > > That's works too. Some means of generic probing is fine. Following > > schemed needs > > more documentation on that usage, as, it is not straight forward compare to > > feature-get framework. Also, on the other thread, we are adding the > > new instructions like > > demote cacheline etc, maybe if the user wants to KNOW if the arch > > supports it then > > the feature-get framework is good. > > If we think, there is no other usecase for generic arch feature-get > > framework then > > we can keep the below scheme else generic arch feature is better for > > more forward > > looking use cases. > > > >> Might be just something like: > >> rte_power_monitor(...) == -ENOTSUP > >> be enough indication for that? > >> So user can just do: > >> if (rte_power_monitor(NULL, 0, 0, 0, 0) == -ENOTSUP) { > >> /* not supported path */ > >> } > >> > >> To check is that feature supported or not. > > > > > > Looking at CLDEMOTE patches, CLDEMOTE is a noop on other archs. I think > we can safely make this intrinsic as a noop on other archs as well, as > it's functionally identical to waking up immediately. > > If we're not creating this for CLDEMOTE, we don't need it here as well. > If we do need it for this, then we arguably need it for CLDEMOTE too.
Sorry I don't understand what you mean, too many "it" and "this" :)
