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

["David Hildenbrand (Arm)" <david@kernel.org>]

On 2/16/26 12:58, Kiryl Shutsemau wrote:
> On Mon, Feb 16, 2026 at 12:45:13PM +0100, David Hildenbrand (Arm) wrote:
>> On 2/16/26 12:34, Kiryl Shutsemau wrote:
>>>
>>> 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.
> 

It's a debug mechanism as stated in the patch description.

Similar to CONFIG_DEBUG_VM slowing your machine down.

> 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.

If you have a good idea, please shoot. I proposed using module parameter 
that
can get toggled more easily by the admin that debugs something.

It's a good question of someone would want to use this mechanism not 
just for debugging. Then, indeed, a more selective (per-process) toggle 
could be warranted. But likely the scanning would in any case be too 
expensive for any non-debug case.

So let's not over-engineer a debug mechanism if this is intended to stay 
a debug mechanism.

-- 
Cheers,

David