Messages in this thread | | | Date | Mon, 9 Jul 2012 23:13:50 +0900 | Subject | Re: [PATCH] mm: don't invoke __alloc_pages_direct_compact when order 0 | From | JoonSoo Kim <> |
| |
2012/7/9 David Rientjes <rientjes@google.com>: > 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.
Only "__alloc_pages_direct_compact()" is not inlined. All others (__alloc_pages_high_priority, __alloc_pages_direct_reclaim, ...) are inlined correctly. So revert is not needed.
I think __alloc_pages_direct_compact() can't be inlined by gcc, because it is so big and is invoked two times in __alloc_pages_nodemask().
> 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 will send result of "make mm/page_alloc.s" to you privately. My environments is "x86_64, GNU C version 4.6.3"
> I'll definitely be following up on this.
Thanks for comments.
| |