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References: <20240417191418.1341988-1-cmllamas@google.com> <20240417191418.1341988-4-cmllamas@google.com>
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From: Alice Ryhl <aliceryhl@google.com>
Date: Thu, 18 Apr 2024 10:21:49 +0200
Message-ID: <CAH5fLghRmYFLa-ag9vo4vv_P281jXGFfsDFyGq5pk5g0PUXtUA@mail.gmail.com>
Subject: Re: [PATCH 3/4] binder: add support for PF_LARGE_HANDLES
To: Carlos Llamas <cmllamas@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>, =?UTF-8?B?QXJ2ZSBIasO4bm5ldsOlZw==?= <arve@android.com>, 
	Todd Kjos <tkjos@android.com>, Martijn Coenen <maco@android.com>, 
	Joel Fernandes <joel@joelfernandes.org>, Christian Brauner <brauner@kernel.org>, 
	Suren Baghdasaryan <surenb@google.com>, linux-kernel@vger.kernel.org, kernel-team@android.com, 
	Tim Murray <timmurray@google.com>
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On Wed, Apr 17, 2024 at 9:15=E2=80=AFPM Carlos Llamas <cmllamas@google.com>=
 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@google.com>
> Suggested-by: Alice Ryhl <aliceryhl@google.com>
> Signed-off-by: Carlos Llamas <cmllamas@google.com>

Reviewed-by: Alice Ryhl <aliceryhl@google.com>