Re: [PATCH 3/4] binder: add support for PF_LARGE_HANDLES

[Alice Ryhl]

On Wed, Apr 17, 2024 at 9:15 PM Carlos Llamas <cmllamas@xxxxxxxxxx> wrote:
>
> Introduce the PF_LARGE_HANDLES flag to enable the use of monotonically
> increasing counters to generate handles. This improves performance in
> transactions when dealing with a large number of references.
>
> The legacy logic performs an inorder traversal of an rbtree to find the
> smallest unused handle. This limitation is due to userspace using the
> handles as indexes (e.g. in vectors). The new logic scales much better
> but requires userspace to support large handle numbers.
>
> The benchmark below with 100,000 references shows the performance gains
> in binder_get_ref_for_node_olocked() calls with PF_LARGE_HANDLES.
>
>   [  167.855945] binder_get_ref_for_node_olocked: 17us (flag on)
>   [  237.088072] binder_get_ref_for_node_olocked: 18178us (flag off)
>
> Suggested-by: Tim Murray <timmurray@xxxxxxxxxx>
> Suggested-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>
> Signed-off-by: Carlos Llamas <cmllamas@xxxxxxxxxx>

Reviewed-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>