On Wed, Jan 15, 2020 at 9:56 AM Aneesh Kumar K.V
<aneesh.ku...@linux.ibm.com> wrote:
>
> On 1/15/20 11:05 PM, Jeff Moyer wrote:
> > "Aneesh Kumar K.V" <aneesh.ku...@linux.ibm.com> writes:
> >
>
> >>>> diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
> >>>> index f2a33f2e3ba8..9126737377e1 100644
> >>>> --- a/include/linux/libnvdimm.h
> >>>> +++ b/include/linux/libnvdimm.h
> >>>> @@ -52,9 +52,9 @@ enum {
> >>>> */
> >>>> ND_REGION_PERSIST_CACHE = 1,
> >>>> /*
> >>>> - * Platform provides mechanisms to automatically flush outstanding
> >>>> - * write data from memory controler to pmem on system power loss.
> >>>> - * (ADR)
> >>>> + * Platform provides instructions to flush data such that on
> >>>> completion
> >>>> + * of the instructions, data flushed is guaranteed to be on pmem even
> >>>> + * in case of a system power loss.
> >>>
> >>> I find the prior description easier to understand.
> >>
> >> I was trying to avoid the term 'automatically, 'memory controler' and
> >> ADR. Can I update the above as
> >
> > I can understand avoiding the very x86-specific "ADR," but is memory
> > controller not accurate for your platform?
> >
> >> /*
> >> * Platform provides mechanisms to flush outstanding write data
> >> * to pmem on system power loss.
> >> */
> >
> > That's way too broad. :) The comments are describing the persistence
> > domain. i.e. if you get data to $HERE, it is guaranteed to make it out
> > to stable media.
>
> With technologies like OpenCAPI, we possibly may not want to call them
> "memory controller"? In a way platform mechanism will flush them such
> that on power failure, it is guaranteed to be on the pmem media. But
> should we call these boundary "memory_controller"? May be we can
> consider "memory controller" an overloaded term there. Considering we
> are calling this as memory_controller for application to parse via
> sysfs, may be the documentation can also carry the same term.
I don't see how OpenCAPI or any other transport has any bearing on the
"memory_controller" term. It's still a controller of persistent memory
and it needs to have the write data received at its buffers / queue to
ensure that the data gets persisted, or, as in the cpu_cache case,
some other agent takes responsibility for shuttling pending writes
that have hit the cache out over the transport to be persisted.
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