From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f169.google.com (mail-pf0-f169.google.com [209.85.192.169]) by kanga.kvack.org (Postfix) with ESMTP id 335D26B0005 for ; Tue, 16 Feb 2016 14:44:17 -0500 (EST) Received: by mail-pf0-f169.google.com with SMTP id x65so110339709pfb.1 for ; Tue, 16 Feb 2016 11:44:17 -0800 (PST) Received: from userp1040.oracle.com (userp1040.oracle.com. [156.151.31.81]) by mx.google.com with ESMTPS id tw5si52972071pac.131.2016.02.16.11.44.16 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 16 Feb 2016 11:44:16 -0800 (PST) From: Vaishali Thakkar Subject: [PATCH] mm/hugetlb: Fix incorrect proc nr_hugepages value Date: Wed, 17 Feb 2016 01:13:26 +0530 Message-Id: <1455651806-25977-1-git-send-email-vaishali.thakkar@oracle.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: 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, Vaishali Thakkar 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. --- 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