Re: [PATCH v2 5/6] alloc_tag: make page allocation tag reference size configurable

[Andrew Morton]

On Sun,  1 Sep 2024 21:41:27 -0700 Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote:

> Introduce CONFIG_PGALLOC_TAG_REF_BITS to control the size of the
> page allocation tag references. When the size is configured to be
> less than a direct pointer, the tags are searched using an index
> stored as the tag reference.
> 
> ...
>
> +config PGALLOC_TAG_REF_BITS
> +	int "Number of bits for page allocation tag reference (10-64)"
> +	range 10 64
> +	default "64"
> +	depends on MEM_ALLOC_PROFILING
> +	help
> +	  Number of bits used to encode a page allocation tag reference.
> +
> +	  Smaller number results in less memory overhead but limits the number of
> +	  allocations which can be tagged (including allocations from modules).
> +

In other words, "we have no idea what's best for you, you're on your
own".

I pity our poor users.

Can we at least tell them what they should look at to determine whether
whatever random number they chose was helpful or harmful?