Binder: fixing contention in buffer allocations
summary
Android binder suffers from alloc-mutex contention when many clients fault pages into a single mmaped service VMA, causing background tasks to hold the mutex while sleeping and high-priority threads to block. The fix is to split buffer setup from page insertion, preallocate pages outside the mutex, and move page faults out of the alloc path so the mutex becomes a spinlock. A synthetic worst-case test shows up to 200% improvement. Followups propose per-binder-page synchronization, RCU/maple tree structures and lockless fault-in retries.
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chapters (6)
- 0:00Introduction to Binder issue
- 1:29Binder memory mapping and contention
- 4:20Mutex contention problem explained
- 7:11Solution and performance improvements
- 9:00Results and test workload
- 10:04Q&A on lock contention
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