From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752669AbZEYSnl (ORCPT ); Mon, 25 May 2009 14:43:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752027AbZEYSnc (ORCPT ); Mon, 25 May 2009 14:43:32 -0400 Received: from courier.cs.helsinki.fi ([128.214.9.1]:53440 "EHLO mail.cs.helsinki.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751190AbZEYSnc (ORCPT ); Mon, 25 May 2009 14:43:32 -0400 Message-ID: <4A1AE5CC.1000209@cs.helsinki.fi> Date: Mon, 25 May 2009 21:39:08 +0300 From: Pekka Enberg User-Agent: Thunderbird 2.0.0.21 (Macintosh/20090302) MIME-Version: 1.0 To: Linus Torvalds 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 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> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Linus, Linus Torvalds wrote: > 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). I can certainly fix that up to use kmalloc() or vmalloc(). I moved it because I wasn't sure how much it's actually allocating and wanted to do the conservative thing here. Linus Torvalds wrote: > 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". SLUB does sysfs setup in kmem_cache_init() and if I saw some oopses if I don't call vfs_caches_init_early() first. I didn't look too closely, though. Linus Torvalds wrote: > I'm also not entirely sure we really need to do vmalloc_init() that early, > but I dunno. It also uses alloc_bootmem(). We can do that later but then we need to fix up vmalloc_init(). There's actually a patch floating around to do that. Pekka