Re: [PATCH 1/2] drivers: android: binder: implement CTABS heuristic

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Jul 15, 2026 at 03:35:51AM +0900, trieu2.huynh wrote:
> Introduce Cluster/Topology-Aware Binder Selection (CTABS) to optimize
> IPC transaction dispatching.
> 
> On asymmetric multi-cluster ARM64 architectures (e.g., big.LITTLE), the
> default binder thread selection algorithm is topology-blind. This leads
> to frequent cross-cluster thread wakeups, resulting in severe CPU cache
> misses, interconnect bottlenecks, and unnecessary cache ping-pongs.
> 
> To mitigate this latency penalty, CTABS evaluates idle waiting threads
> based on their last-executed CPU ID and prioritizing them as follows:
> 
> (*) Immediate Selection: Favors threads whose last-executed CPU matches
>     the caller's CPU exactly, exiting the selection loop early to ensure
>     optimal L1/L2 cache locality.
> (*) Cluster Match: Selects threads that ran on the same CPU cluster as
>     the caller, maximizing local cache reuse.
> (*) Cross-Cluster: Falls back to any available thread across different
>     clusters if no local affinity is found.
> 
> This topology prioritization maximizes CPU cache reuse, minimizes inter-
> cluster snooping overhead, and significantly reduces overall transaction
> turnaround latency on modern multi-cluster SoCs.
> 
> Signed-off-by: trieu2.huynh <trieu2.huynh@lge.corp-partner.google.com>

We need a real name here, and a real email address, not a
partner.google.com one.

thanks,

greg k-h