From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753415AbZEYQlu (ORCPT ); Mon, 25 May 2009 12:41:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752039AbZEYQlm (ORCPT ); Mon, 25 May 2009 12:41:42 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:39871 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752005AbZEYQll (ORCPT ); Mon, 25 May 2009 12:41:41 -0400 Date: Mon, 25 May 2009 09:39:36 -0700 (PDT) From: Linus Torvalds X-X-Sender: torvalds@localhost.localdomain To: Pekka J Enberg cc: Nick Piggin , Ingo Molnar , Yinghai Lu , Rusty Russell , "H. Peter Anvin" , Jeff Garzik , Alexander Viro , Linux Kernel Mailing List , Andrew Morton , Peter Zijlstra , cl@linux-foundation.org, mpm@selenic.com Subject: Re: [GIT PULL] scheduler fixes In-Reply-To: Message-ID: References: <20090518202031.GA26549@elte.hu> <4A199327.5030503@kernel.org> <20090525025353.GA2580@elte.hu> <4A1A2261.1000504@kernel.org> <20090525051521.GC23032@elte.hu> <20090525112504.GB24071@wotan.suse.de> <84144f020905250437x585e66a2oc1124a4f1f43059d@mail.gmail.com> <20090525114127.GE24071@wotan.suse.de> User-Agent: Alpine 2.01 (LFD 1184 2008-12-16) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 25 May 2009, Pekka J Enberg wrote: > diff --git a/init/main.c b/init/main.c > index 33ce929..fb0e004 100644 > --- a/init/main.c > +++ b/init/main.c > @@ -576,6 +576,22 @@ asmlinkage void __init start_kernel(void) > setup_nr_cpu_ids(); > smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */ > > + build_all_zonelists(); > + page_alloc_init(); > + > + printk(KERN_NOTICE "Kernel command line: %s\n", boot_command_line); > + parse_early_param(); > + parse_args("Booting kernel", static_command_line, __start___param, > + __stop___param - __start___param, > + &unknown_bootoption); > + pidhash_init(); > + vmalloc_init(); > + vfs_caches_init_early(); > + /* > + * Set up kernel memory allocators > + */ > + mem_init(); > + kmem_cache_init(); So what strikes me is a question: - why do we want to do pidhash_init and vfs_caches_init_early() so early? Yes, pidhash_init() now uses alloc_bootmem. It's an allocation that is not trivially small, but it's not humongous either (max 4096 hash list heads, one pointer each). And vfs_caches_init_early() is actually doing some rather strange things, like doing a "alloc_large_system_hash()" but not unconditionally: it does it in the "late" initialization too, if not done early. inode_init_early does soemthing very similar (ie a _conditional_ early init). So none of this seems to really get a huge advantage from the early init. There seems to be some subtle NUMA issues, but do we really want that? I get the feeling that nobody ever wanted to do it early, and then the NUMA people said "I don't wnt to do this early, but I don't want to touch the non-NUMA case, so I'll do it early for non-numa, and late for numa". I'm also not entirely sure we really need to do vmalloc_init() that early, but I dunno. It also uses alloc_bootmem(). Linus