Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161315Ab3DEJaj (ORCPT ); Fri, 5 Apr 2013 05:30:39 -0400 Received: from cantor2.suse.de ([195.135.220.15]:48267 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161203Ab3DEJah (ORCPT ); Fri, 5 Apr 2013 05:30:37 -0400 Date: Fri, 5 Apr 2013 11:30:34 +0200 From: Michal Hocko To: Simon Jeons Cc: Linux Memory Management List , Andrew Morton , Mel Gorman , Hugh Dickins , KOSAKI Motohiro , Andi Kleen , Linux kernel Mailing List , Naoya Horiguchi , David Rientjes Subject: Re: [RFC][PATCH 0/9] extend hugepage migration Message-ID: <20130405093034.GB31132@dhcp22.suse.cz> References: <1361475708-25991-1-git-send-email-n-horiguchi@ah.jp.nec.com> <5148F830.3070601@gmail.com> <1363815326-urchkyxr-mutt-n-horiguchi@ah.jp.nec.com> <514A4B1C.6020201@gmail.com> <20130321125628.GB6051@dhcp22.suse.cz> <514B9BD8.9050207@gmail.com> <20130322081532.GC31457@dhcp22.suse.cz> <515E2592.7020607@gmail.com> <20130405080828.GA14882@dhcp22.suse.cz> <515E92CA.4000507@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <515E92CA.4000507@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3169 Lines: 75 On Fri 05-04-13 17:00:58, Simon Jeons wrote: > Hi Michal, > On 04/05/2013 04:08 PM, Michal Hocko wrote: > >On Fri 05-04-13 09:14:58, Simon Jeons wrote: > >>Hi Michal, > >>On 03/22/2013 04:15 PM, Michal Hocko wrote: > >>>[getting off-list] > >>> > >>>On Fri 22-03-13 07:46:32, Simon Jeons wrote: > >>>>Hi Michal, > >>>>On 03/21/2013 08:56 PM, Michal Hocko wrote: > >>>>>On Thu 21-03-13 07:49:48, Simon Jeons wrote: > >>>>>[...] > >>>>>>When I hacking arch/x86/mm/hugetlbpage.c like this, > >>>>>>diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c > >>>>>>index ae1aa71..87f34ee 100644 > >>>>>>--- a/arch/x86/mm/hugetlbpage.c > >>>>>>+++ b/arch/x86/mm/hugetlbpage.c > >>>>>>@@ -354,14 +354,13 @@ hugetlb_get_unmapped_area(struct file *file, > >>>>>>unsigned long addr, > >>>>>> > >>>>>>#endif /*HAVE_ARCH_HUGETLB_UNMAPPED_AREA*/ > >>>>>> > >>>>>>-#ifdef CONFIG_X86_64 > >>>>>>static __init int setup_hugepagesz(char *opt) > >>>>>>{ > >>>>>>unsigned long ps = memparse(opt, &opt); > >>>>>>if (ps == PMD_SIZE) { > >>>>>>hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT); > >>>>>>- } else if (ps == PUD_SIZE && cpu_has_gbpages) { > >>>>>>- hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT); > >>>>>>+ } else if (ps == PUD_SIZE) { > >>>>>>+ hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT+4); > >>>>>>} else { > >>>>>>printk(KERN_ERR "hugepagesz: Unsupported page size %lu M\n", > >>>>>>ps >> 20); > >>>>>> > >>>>>>I set boot=hugepagesz=1G hugepages=10, then I got 10 32MB huge pages. > >>>>>>What's the difference between these pages which I hacking and normal > >>>>>>huge pages? > >>>>>How is this related to the patch set? > >>>>>Please _stop_ distracting discussion to unrelated topics! > >>>>> > >>>>>Nothing personal but this is just wasting our time. > >>>>Sorry kindly Michal, my bad. > >>>>Btw, could you explain this question for me? very sorry waste your time. > >>>Your CPU has to support GB pages. You have removed cpu_has_gbpages test > >>>and added a hstate for order 13 pages which is a weird number on its > >>>own (32MB) because there is no page table level to support them. > >>But after hacking, there is /sys/kernel/mm/hugepages/hugepages-*, > >>and have equal number of 32MB huge pages which I set up in boot > >>parameter. > >because hugetlb_add_hstate creates hstate for those pages and > >hugetlb_init_hstates allocates them later on. > > > >>If there is no page table level to support them, how can > >>them present? > >Because hugetlb hstate handling code doesn't care about page tables and > >the way how those pages are going to be mapped _at all_. Or put it in > >another way. Nobody prevents you to allocate order-5 page for a single > >pte but that would be a pure waste. Page fault code expects that pages > >with a proper size are allocated. > Do you mean 32MB pages will map to one pmd which should map 2MB pages? > Please refer to hugetlb_fault for more information. -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/