Hallo,
I'm thinking about dropping the x86-64 CONFIG_REORDER for 2.6.22.
The function enabled -ffunction-sections and then tries to reorder
the executable
While that's in theory a worthy goal to save TLB/icache, in practice it
didn't really work out.
Rationale:
- It cannot be enabled in normal builds because all current lds
become very slow when they have to handle thousands of sections.
- The list of hot functions it needs - arch/x86_64/kernel/functionlist -
hasn't been changed for a long time and is already out of date.
I also don't know no sane way to keep it uptodate. Profile feedback
at runtime is not practical for the kernel and even if it's questionable
we would find a good training workload. Trying to change the manually
is imho foolish and likely not too useful anyways (if any hot function
is missed the TLB savings will be lost and it is unlikely we can
get 100% coverage)
- The workloads of the kernel are too diverse to make this concept
really work
So I'm planning to drop the option and arch/x86_64/kernel/functionlist
Comments?
-Andi
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