Re: [LSF/MM/BPF] Improving MGLRU

[Barry Song <21cnbao@gmail.com>]

> 4. MGLRU's swappiness is kind of useless in some situations compared to
>   Active / Inactive LRU, since its force protects the youngest two gen, so
>   quite often we can only reclaim one type of folios. To workaround that, the
>   user usually runs force aging before reclaim. So, can we just remove the
>   force protection of the youngest two gens?

I guess not—MGLRU needs at least two generations to function,
similar to active and inactive lists, meaning it requires two lists.

You Zhao mentioned this in commit ec1c86b25f4b:
"This protocol, AKA second chance, requires a minimum of two
generations, hence MIN_NR_GENS."

But I do feel the issue is that anon and file folios currently share
the same generations. This may make anon and file be reclaimed more
fairly, but isn’t swappiness meant to allow some imbalance? Sharing
generations causes them to keep catching up with each other. We might
consider providing separate generations for them.

Thanks
Barry