Re: [RFC PATCH 5/8] mm/vmalloc: map contiguous pages in batches for vmap() if possible

[Dev Jain]

On 08/04/26 8:21 am, Barry Song (Xiaomi) wrote:
> In many cases, the pages passed to vmap() may include high-order
> pages allocated with __GFP_COMP flags. For example, the systemheap
> often allocates pages in descending order: order 8, then 4, then 0.
> Currently, vmap() iterates over every page individually—even pages
> inside a high-order block are handled one by one.
> 
> This patch detects high-order pages and maps them as a single
> contiguous block whenever possible.
> 
> An alternative would be to implement a new API, vmap_sg(), but that
> change seems to be large in scope.
> 
> Signed-off-by: Barry Song (Xiaomi) <baohua@xxxxxxxxxx>
> ---

Coincidentally, I was working on the same thing :)

We have a usecase regarding Arm TRBE and SPE aux buffers.

I'll take a look at your patches later, but my implementation is the
following, if you have any comments. I have squashed the patches into
a single diff.