2012/7/9 David Rientjes <[email protected]>: > 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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
