Re: [PATCH] mm: Add AnonZero accounting for zero-filled anonymous pages

[Matthew Wilcox <willy@infradead.org>]

On Mon, Feb 16, 2026 at 04:54:05PM +0000, Kiryl Shutsemau wrote:
> What I would like to see in the kernel is a syscall that return the
> memory stats in binary form. Something like
> 
> size_t memstat(int pidfd, struct memstat memstatbuf[], size_t n,
> 		unsigned long flags, unsigned long start, unsigned long end);
> 
> The syscall will fill up to n memstatbufs, one per-VMA. What exactly
> filled there defined by flags. The return value is how many memstatbuf
> is populated. The caller can call it multiple times to walk address
> space it is interested in.
> 
> We also can have a flag that mirrors smaps_rollup behaviour and collect
> all the data into a single memstatbuf.

But is that what we want?  Let's say a process allocates a 2MB THP, uses
12kB of it and then forks.  A lot.  Now all children that haven't called
exec() see the wasted 2036kB.  Would we rather have something that scans
(say) the LRU list looking for zero memory?