Re: [PATCH 2/2] crypto: deflate - use vmalloc() for stream workspaces

[Johannes Weiner]

On Wed, Nov 11, 2026 at 07:07:40AM -0800, Usama Arif wrote:
> The deflate acomp streams outlive the transforms that use them. One
> stream is allocated during transform initialization; additional
> per-CPU streams are allocated on demand. They are freed only when
> the algorithm is unregistered.
> 
> In a 4 KiB-page x86-64 build, each stream requests 145,320 bytes.
> If kvmalloc() succeeds via kmalloc(), it occupies an order-6 block
> (256 KiB). vmalloc() needs 36 backing pages (144 KiB), 112 KiB fewer
> per stream. Across 384 populated streams, that is 42 MiB less
> workspace backing if all would have used kmalloc(). There is no such
> gain when kvmalloc() already falls back to vmalloc().
> 
> Use vmalloc() and vfree() directly, as the crypto lz4 implementations
> already do. This uses vmalloc address space, page tables and
> bookkeeping; the figures above compare workspace backing only.
> 
> Signed-off-by: Usama Arif <usama.arif@xxxxxxxxx>

Reviewed-by: Johannes Weiner <hannes@xxxxxxxxxxx>