A write-combined CPU cache mode that is optimized for resources that the CPU writes into, but never reads.
- iOS 8.0+
- macOS 10.11+
- Mac Catalyst 13.0+
- tvOS 9.0+
Write-combined memory is optimized for resources that the CPU writes into, but never reads. On some implementations, writes may bypass caches to avoid cache pollution. Read actions may perform very poorly.
Applications should use write combining only if writing to normally cached buffers is known to cause performance issues due to cache pollution, as write-combined memory can have surprising performance pitfalls. Another approach is to use non-temporal writes to normally cached memory (STNP on ARMv8, _mm_stream_* on x86_64).