On 12.09.25 17:44, Kiryl Shutsemau wrote:

On Fri, Sep 12, 2025 at 04:39:02PM +0100, Kiryl Shutsemau wrote:

quoted

quoted

Shower thought: it might be in these cases especially where the FreeBSD
reservation system comes in handy - best effort allocating a THP, but not
actually mapping it as such until you really _know_ it is hot - and until
then, memory reclaim can just break your THP down if it really needs to.

This is just silly. All downsides without benefit until maybe later. And
for short-lived processes the "later" never comes.

The right way out is to get better info on access pattern from hardware.
For instance, if we move access bit out of page table entry and make it
independent of the actually mapping size that would give us much better
view on what actually is going on.

We discussed this a couple of times in the past, the problem is that it 
does not help anybody really if all but a handful piece of hardware 
provides such a features.

Long long long term I agree, short term we cannot really build core 
infrastructure around any of that.

-- 
Cheers

David / dhildenb