RE: [EXT] Re: [RFC 00/12] ARM: MPAM: add support for priority partitioning control

From: Luck, Tony
Date: Thu Jan 11 2024 - 18:14:48 EST


>> I'm not sure having multiple lines for the same resource makes anything
>> clearer. I preferred one of the earlier proposals like this one:
>>
>> L3:0=XXXX,PPART=X,CCAP=X;1=YYYY,CCAP=Y
>
> This assumes that all tools (public and private) that currently parse the schemata
> file will be able to handle this additional information seamlessly.

Reinette,

Yes. If there are tools that *read* schemata files, they will be surprised by this extra information.

But that also applies if the "extra" information is moved to a second line that also begins with "L3:".

Tools that *write* schemata files should be OK as long as the kernel will still accept:

# echo "L3:1=fff" > schemata

E.g. the Linux selftests in tools/testing/selftests/resctrl/ should still run without
any modification.

The "separate line" option could work if the prefix isn't "L3:". E.g.

L3:0=XXXX;1=YYYY
L3PPART:0=X
L3CCAP:0=X;1=Y

If these options are asymmetrically available on cache instances, these extra
lines won't have every L3 cache instance listed.

-Tony