From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx106.postini.com [74.125.245.106]) by kanga.kvack.org (Postfix) with SMTP id 4770E6B0093 for ; Sun, 8 Jul 2012 18:53:38 -0400 (EDT) Received: by pbbrp2 with SMTP id rp2so22055293pbb.14 for ; Sun, 08 Jul 2012 15:53:37 -0700 (PDT) Date: Sun, 8 Jul 2012 15:53:35 -0700 (PDT) From: David Rientjes Subject: Re: [PATCH] mm: don't invoke __alloc_pages_direct_compact when order 0 In-Reply-To: Message-ID: References: <1341588521-17744-1-git-send-email-js1304@gmail.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton , Mel Gorman , JoonSoo Kim Cc: Pekka Enberg , Christoph Lameter , linux-kernel@vger.kernel.org, linux-mm@kvack.org 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. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org