[...]
towards David's earlier simplified approach:
max_ptes_none == 511 -> collapse mTHP always
max_ptes_none != 511 -> collapse mTHP only if all PTEs are non-none/zero
Pretty sure David's suggestion was that max_ptes_none would literally get set to
511 if you specified 511, or 0 if you specified anything else.
We had multiple incarnations of this approach, but the first one really was:
max_ptes_none == 511 -> collapse mTHP always
max_ptes_none == 0 -> collapse mTHP only if all non-none/zero
And for the intermediate values
(1) pr_warn() when mTHPs are enabled, stating that mTHP collapse is not
supported yet with other values
(2) treat it like max_ptes_none == 0 or (maybe better?) just disable
mTHP collapse
I still like that approach because it let's us defer solving the creep
problem later and doesn't add a silent capping.
Using intermediate max_ptes_none values are really only reasonable with
the deferred shrinker today. And that one does not support mTHP even
with this series, so it's future work either way.
--
Cheers
David / dhildenb
