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

[Trieu Huynh]

On Wed, Jul 15, 2026 at 07:55:17AM +0200, Greg KH wrote:
> 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@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
> 
> We need a real name here, and a real email address, not a
> partner.google.com one.
Thanks. I'll correct it in v2.
> 
> thanks,
> 
> greg k-h