On Sun, 8 Jul 2012, JoonSoo Kim wrote:
> >> __alloc_pages_direct_compact has many arguments so invoking it is very costly.
> >> And in almost invoking case, order is 0, so return immediately.
> >>
> >
> > If "zero cost" is "very costly", then this might make sense.
> >
> > __alloc_pages_direct_compact() is inlined by gcc.
>
> In my kernel image, __alloc_pages_direct_compact() is not inlined by gcc.
Adding Andrew and Mel to the thread since this would require that we
revert 11e33f6a55ed ("page allocator: break up the allocator entry point
into fast and slow paths") which would obviously not be a clean revert
since there have been several changes to these functions over the past
three years.
I'm stunned (and skeptical) that __alloc_pages_direct_compact() is not
inlined by your gcc, especially since the kernel must be compiled with
optimization (either -O1 or -O2 which causes these functions to be
inlined). What version of gcc are you using and on what architecture?
Please do "make mm/page_alloc.s" and send it to me privately, I'll file
this and fix it up on gcc-bugs.
I'll definitely be following up on this.
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