Re: [PATCH v2 0/8] Introduce a huge-page pre-zeroing mechanism

[Gregory Price <gourry@gourry.net>]

On Tue, Jan 20, 2026 at 01:18:19PM -0500, Gregory Price wrote:
> This is a trivial example, but it's unclear zero_on_free actually
> provides a benefit.  You have to know ahead of time what the runtime
> behavior, pre-zeroed count, and allocation pattern (0->10->5->...) would
> be to determine whether there's an actual reduction in startup time.
> 
> But just trivially, starting from the base case of no pages being
> zeroed, you're just injecting an additional zero(X) cost if program_a()
> consumes more hugepages than program_b().
> 
> Long way of saying the shift from alloc to free seems heuristic-y and
> you need stronger analysis / better data to show this change is actually
> beneficial in the general case.
> 

As an addendum to this:  Maybe this is an indication that a global
switch (per-node sysfs entry) is not the best decision, and that maybe
there's a better way to accomplish this with a reduced scope.

hugetlb-only sysfs knob
	- same issue as current proposal, but better placed
	  why would you only apply this on one node?

prctl thingy
	- limits effects to just those opting into alloc-on-free
	- probably still needs hugetlb-internal zeroed-pages tracking
	  but doesn't require the rest of the machinery

do it entirely in userland
	- modify the software to zero before exit
	- use MAP_UNINITIALIZED
	- useful and simple if your hugetlb use case is homogenous

there's probably more oprtions

~Gregory