a question about run-time patching for heterogeneous cores.
The current code for arm64 run-time patching works fine if all CPUs are the same, but doesn't seem to handle the case when CPUs are of different type. For example, when you have a mix of A53 and A57 cores, currently the errata WARs can be applied irrespective of A53 or A57 since the code in need of patching are shared.
It doesn't look like the current WARs will cause functional problems across different CPU cores. On the other hand, is there a perf issue due to the same errata WARs being applied to different cores?
Thanks
Bo
Quoted 10 lines · Bo Yan
The current code for arm64 run-time patching works fine if all CPUs are the same, but doesn't seem to handle the case when CPUs are of different type. For example, when you have a mix of A53 and A57 cores, currently the errata WARs can be applied irrespective of A53 or A57 since the code in need of patching are shared.
It doesn't look like the current WARs will cause functional problems across different CPU cores. On the other hand, is there a perf issue due to the same errata WARs being applied to different cores?
There may be some cost in an unaffected core executing the workaround code, though this is very dependent on the particular CPU and workaround, and in some cases the cost may not be measurable.
Where possible we attempt to use workarounds which are not excessively expensive on particular cores in common pairings.
Thanks,
Mark.