Re: [PATCH 6/8] mm/zsmalloc, zswap: Handle objcg charging and lifetime in zsmalloc

[Yosry Ahmed]

> > AFAICT the only zswap-specific part is the actual stat indexes, what
> > if these are parameterized at the zsmalloc pool level? AFAICT zswap
> > and zram will never share a pool.
>
> TBH, if we were to start from scratch, these should be zsmalloc
> counters not zswap counters. Only zsmalloc knows about the memory
> placement and real memory consumption (i.e taking into account
> intra-slot wasted space) - this information is abstracted away from
> all of the callers.

I agree, but we cannot change the zswap stats now that we added them.
Keep in mind that when they were added zsmalloc was not the only
backend.

> And if/when zram supports cgroup tracking, memory
> used by zswap and memory used by zram is indistinguishable, no?

It is distinguishable as long as they use different zsmalloc pools, I
don't see why we'd need to share a pool.

> Anyway, Joshua, do you think this is doable? Seems promising to me,
> but idk if it will be clean to implement or not.

Not sure what you mean here? Changing the stats to be zsmalloc-based?
IIUC we can't do this without breaking userspace.