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

[Kiryl Shutsemau <kirill@shutemov.name>]

On Mon, Feb 16, 2026 at 12:45:13PM +0100, David Hildenbrand (Arm) wrote:
> On 2/16/26 12:34, Kiryl Shutsemau wrote:
> > On Sat, Feb 14, 2026 at 04:45:14PM +0800, Wenchao Hao wrote:
> > > Add kernel command line option "count_zero_page" to track anonymous pages
> > > have been allocated and mapped to userspace but zero-filled.
> > > 
> > > This feature is mainly used to debug large folio mechanism, which
> > > pre-allocates and map more pages than actually needed, leading to memory
> > > waste from unaccessed pages.
> > > 
> > > Export the result in /proc/pid/smaps as "AnonZero" field.
> > 
> > I expect it to slowdown /proc/pid/smaps read substantially. I don't
> > think this line in smaps worth it.
> > 
> 
> That's why it's enabled through a command line parameter.

One users want the stat and all users on the machine pay the price?
That's a poor trade off.

In general, smaps scales poorly. It collects a lot of stats and most of
them are ignored by user. We need something like statx(2) where user can
declare what he is interested in, so kernel won't waste cycles.

Kernel cmdline parameter is the wrong place to declare what stats you
want to see.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov