Re: [PATCH] rust_binder: speed up get_node_debug_info using lower_bound iter

On Mon, Jul 27, 2026 at 10:22:18PM -0300, Rafael Passos wrote:
> Finding the next node in the RBTree can be done more efficiently using
> the cursor_lower_bound, as it reduces cost from O(n) to O(log n).
> 
> Link: https://github.com/Rust-for-Linux/linux/issues/1249
> Suggested-by: Alice Ryhl <[email protected]>
> Signed-off-by: Rafael Passos <[email protected]>
> ---
> 
> (Sorry for the resend, my script missed the list)
> 
> Hi, I decided to use the peek_next semantic instead of a loop/break.
> Since the iterator should land directly on ptr or greater, I think this
> is more elegant this way. But I can change it otherwise.
> 
> Thanks,
> Rafael
> 
> 
>  drivers/android/binder/process.rs | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/android/binder/process.rs b/drivers/android/binder/process.rs
> index cdd1a90797266..c0c2112aca1c6 100644
> --- a/drivers/android/binder/process.rs
> +++ b/drivers/android/binder/process.rs
> @@ -1174,10 +1174,15 @@ fn get_node_debug_info(&self, data: UserSlice) -> Result {
>  
>          {
>              let inner = self.inner.lock();
> -            for (node_ptr, node) in &inner.nodes {
> +            let cursor = inner.nodes.cursor_lower_bound(&ptr);
> +            if let Some(c) = cursor {
> +                let (node_ptr, node) = c.current();
>                  if *node_ptr > ptr {
>                      node.populate_debug_info(&mut out, &inner);
> -                    break;
> +                } else if *node_ptr == ptr {
> +                    if let Some((_, next_node)) = c.peek_next() {
> +                        next_node.populate_debug_info(&mut out, &inner);
> +                    }
>                  }
>              }
>          }
> -- 
> 2.53.0
> 

This would be a lot simpler if you just did `cursor_lower_bound(ptr+1)`
so that you go straight to the right target node, instead of doing this
if/else logic.

Alice