From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933657AbcBQJ7m (ORCPT ); Wed, 17 Feb 2016 04:59:42 -0500 Received: from mail-wm0-f48.google.com ([74.125.82.48]:37527 "EHLO mail-wm0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932209AbcBQJ7j (ORCPT ); Wed, 17 Feb 2016 04:59:39 -0500 Date: Wed, 17 Feb 2016 11:59:35 +0200 From: "Kirill A. Shutemov" To: Vaishali Thakkar Cc: Andrew Morton , n-horiguchi@ah.jp.nec.com, mike.kravetz@oracle.com, hillf.zj@alibaba-inc.com, kirill.shutemov@linux.intel.com, dave.hansen@linux.intel.com, paul.gortmaker@windriver.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/hugetlb: Fix incorrect proc nr_hugepages value Message-ID: <20160217095935.GA15769@node.shutemov.name> References: <1455651806-25977-1-git-send-email-vaishali.thakkar@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1455651806-25977-1-git-send-email-vaishali.thakkar@oracle.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 17, 2016 at 01:13:26AM +0530, Vaishali Thakkar wrote: > Currently incorrect default hugepage pool size is reported by proc > nr_hugepages when number of pages for the default huge page size is > specified twice. > > When multiple huge page sizes are supported, /proc/sys/vm/nr_hugepages > indicates the current number of pre-allocated huge pages of the default > size. Basically /proc/sys/vm/nr_hugepages displays default_hstate-> > max_huge_pages and after boot time pre-allocation, max_huge_pages should > equal the number of pre-allocated pages (nr_hugepages). > > Test case: > > Note that this is specific to x86 architecture. > > Boot the kernel with command line option 'default_hugepagesz=1G > hugepages=X hugepagesz=2M hugepages=Y hugepagesz=1G hugepages=Z'. After > boot, 'cat /proc/sys/vm/nr_hugepages' and 'sysctl -a | grep hugepages' > returns the value X. However, dmesg output shows that Z huge pages were > pre-allocated. > > So, the root cause of the problem here is that the global variable > default_hstate_max_huge_pages is set if a default huge page size is > specified (directly or indirectly) on the command line. After the > command line processing in hugetlb_init, if default_hstate_max_huge_pages > is set, the value is assigned to default_hstae.max_huge_pages. However, > default_hstate.max_huge_pages may have already been set based on the > number of pre-allocated huge pages of default_hstate size. > > The solution to this problem is if hstate->max_huge_pages is already set > then it should not set as a result of global max_huge_pages value. > Basically if the value of the variable hugepages is set multiple times > on a command line for a specific supported hugepagesize then proc layer > should consider the last specified value. > > Signed-off-by: Vaishali Thakkar > --- > The patch contains one line over 80 characters as I think limiting that > line to 80 characters makes code look bit ugly. But if anyone is having > issue with that then I am fine with limiting it to 80 chracters. What about this? if (default_hstate_max_huge_pages && !default_hstate.max_huge_pages) default_hstate.max_huge_pages = default_hstate_max_huge_pages; > --- > mm/hugetlb.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 06ae13e..01f2b48 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -2630,8 +2630,10 @@ static int __init hugetlb_init(void) > hugetlb_add_hstate(HUGETLB_PAGE_ORDER); > } > default_hstate_idx = hstate_index(size_to_hstate(default_hstate_size)); > - if (default_hstate_max_huge_pages) > - default_hstate.max_huge_pages = default_hstate_max_huge_pages; > + if (default_hstate_max_huge_pages) { > + if (!default_hstate.max_huge_pages) > + default_hstate.max_huge_pages = default_hstate_max_huge_pages; > + } > > hugetlb_init_hstates(); > gather_bootmem_prealloc(); > -- > 2.1.4 > > -- > 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 -- Kirill A. Shutemov