Need specific references to the hardware interrupt latency for the ARMv8 Cortex-A53. interrupt latency from when an interrupt is triggered to when the ISR is initially invoked, but not including operating system, kernel, or application latency.
Hi Tracy,
It's a good question and I get where you are coming from, I'm not sure not sure there is a simple answer that we can give from the CPU point of view other than "empirically measure it on your platform". There are many different ARM chipset vendors with very different memory systems and cache sizes, and how the OS is configured will also impact this, so there isn't a neat single answer here.
Based on my past experience with Linux and phone chipsets my gut feel is that 1us seems rather tight for a realtime deadline on an A-profile core; assuming a 1GHz CPU frequency that's only 1000 cycles and you don't need much to go wrong in terms of cache or TLB misses to violate that.
If there are constraints you can play with your CPU partitioning then you may get close to this. If you dedicate a single core to running only the critical part of the interrupt handler so it stays inside the L1 cache and uTLB, and don't run anything else on that core then you can artificially encourage "good" cache hit rates, but that would involve not using that core for anything else and even then it will depend how much shared data you have (memory coherency will mean any shared cache lines may be pulled out of the L1 by other CPUs needing that cache line).
Keeping things hot in the L2 may be possible, but will depends on the size of the L2 vs the total size of code and data that is running on all CPUs. It's a shared cache across all of the cores, so other CPUs doing other work may push the critical stuff out of the L2 cache - so you're just playing with statistical improvement not guaranteed real-time performance.
Cheers, Pete