On 11.11.2021 18:57, Andrew Cooper wrote:
> Function pointers are expensive, and the raw parameter is a constant from all
> callers, meaning that it predicts very well with local branch history.
The code change is fine, but I'm having trouble with "all" here: Both
functions aren't even static, so while callers in io_apic.c may
benefit (perhaps with the exception of ioapic_{read,write}_entry(),
depending on whether the compiler views inlining them as warranted),
I'm in no way convinced this extends to the callers in VT-d code.
Further ISTR clang being quite a bit less aggressive about inlining,
so the effects might not be quite as good there even for the call
sites in io_apic.c.
Can you clarify this for me please?
Jan
