On Fri, 29 Jan 2021 17:11:03 +0000
Vijayenthiran Subramanian <vijayenthiran.subraman...@arm.com> wrote:
Hi Vijayenthiran,
....
> > > > + // Memory Proximity Domain
> > > > + {
> > > > +
> > > > EFI_ACPI_6_3_HMAT_STRUCTURE_MEMORY_PROXIMITY_DOMAIN_ATTRIBUTES_INIT (
> > > > + 1, 0x0, 0x0),
> > > > +
> > > > EFI_ACPI_6_3_HMAT_STRUCTURE_MEMORY_PROXIMITY_DOMAIN_ATTRIBUTES_INIT (
> > > > + 1, 0x1, 0x1),
> > > > + },
> > > > +
> > > > + // Latency Info
> > > > +
> > > > EFI_ACPI_6_3_HMAT_STRUCTURE_SYSTEM_LOCALITY_LATENCY_AND_BANDWIDTH_INFO_INIT
> > > > (
> > > > + 0, 0, INITATOR_PROXIMITY_DOMAIN_CNT, TARGET_PROXIMITY_DOMIAIN_CNT,
> > > > 100),
> > > > + {
> > > > + {0, 1}, {0, 1},
> > > > + {
> > > > + 10, 20,
> > > > + 20, 10,
> > > > + }
> > > > + },
> >
> > Hi,
> >
> > Now either you have a very odd machine in which latencies are round numbers
> > that happen
> > to look like the values in SLIT or ... ?
> >
> > HMAT has very carefully defined real world units to overcome the fact that
> > there
> > was no standard scaling etc for SLIT. It is not a good idea to put tables
> > out
> > there which don't do this right as someone may copy this for a real system
> > and we end up with HMAT being roughly as useless for performance prediction
> > as
> > SLIT is. That is not something I would want to see.
> >
> > Jonathan
>
> This patch is for a platform that is modelled and not for an actual board. So
> the latencies are hypothetical but ensure that the typical latency between two
> chips is represented. These tables are not expected to be copied for another
> platform without understanding what these values mean. Such a copy, without
> understanding what is being copied, would be an error in judgement on the part
> of the person doing it. The commit message of this patch (in v2) can be
> updated
> to exercise caution on reusing these values.
>
> [1]: https://developer.arm.com/products/system-design/fixed-virtual-platforms
No one reads commit messages. So if you want to avoid people copying them put a
comment in the actual file. Or just make up some more plausible numbers :)
All we really need here is to avoid giving the impression that copying numbers
from
SLIT is valid.
Jonathan
>
> Best Regards,
> Vijayenthiran
>
> >
> > > > +
> > > > + // Memory Side Cache
> > > > + EFI_ACPI_6_3_HMAT_STRUCTURE_MEMORY_SIDE_CACHE_INFO_INIT (
> > > > + 0x0, SIZE_8MB,
> > > > + HMAT_STRUCTURE_MEMORY_SIDE_CACHE_INFO_CACHE_ATTRIBUTES_INIT (
> > > > + 1,
> > > > + 1,
> > > > + 2,
> > > > + 2,
> > > > + 64 // 64 bytes cache line length
> > > > + ),
> > > > + 0),
> > > > +
> > > > + EFI_ACPI_6_3_HMAT_STRUCTURE_MEMORY_SIDE_CACHE_INFO_INIT (
> > > > + 0x1, SIZE_8MB,
> > > > + HMAT_STRUCTURE_MEMORY_SIDE_CACHE_INFO_CACHE_ATTRIBUTES_INIT (
> > > > + 1,
> > > > + 1,
> > > > + 2,
> > > > + 2,
> > > > + 64 // 64 bytes cache line length
> > > > + ),
> > > > + 0),
> > > > +};
> > > > +
> > > > +VOID* CONST ReferenceAcpiTable = &Hmat;
> > >
> > >
> > >
> > >
> > >
> > >
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