Re: [RFC PATCH v3 0/4] Node Weights and Weighted Interleave

Huang, Ying
2023-11-03T07:12:49Z

Michal Hocko <mhocko@suse.com> writes:

> On Thu 02-11-23 14:11:09, Huang, Ying wrote:
>> Michal Hocko <mhocko@suse.com> writes:
>>
>> > On Wed 01-11-23 10:21:47, Huang, Ying wrote:
>> >> Michal Hocko <mhocko@suse.com> writes:
>> > [...]
>> >> > Well, I am not convinced about that TBH. Sure it is probably a good fit
>> >> > for this specific CXL usecase but it just doesn't fit into many others I
>> >> > can think of - e.g. proportional use of those tiers based on the
>> >> > workload - you get what you pay for.
>> >>
>> >> For "pay", per my understanding, we need some cgroup based
>> >> per-memory-tier (or per-node) usage limit. The following patchset is
>> >> the first step for that.
>> >>
>> >> https://lore.kernel.org/linux-mm/cover.1655242024.git.tim.c.chen@linux.intel.com/
>> >
>> > Why do we need a sysfs interface if there are plans for cgroup API?
>>
>> They are for different target. The cgroup API proposed here is to
>> constrain the DRAM usage in a system with DRAM and CXL memory. The less
>> you pay, the less DRAM and more CXL memory you use.
>
> Right, but why the usage distribution requires its own interface and
> cannot be combined with the access control part of it?

Per my understanding, they are orthogonal.

Weighted-interleave is a memory allocation policy, other memory
allocation policies include local first, etc.

Usage limit is to constrain the usage of specific memory types
(e.g. DRAM) for a cgroup. It can be used together with local first
policy and some other memory allocation policy.

--
Best Regards,
Huang, Ying