From f8b74815a452ff2904b5d7fcce1a5ae2a4d7ca5e Mon Sep 17 00:00:00 2001 From: Vaishali Thakkar Date: Wed, 17 Feb 2016 13:11:26 -0800 Subject: mm/hugetlb.c: fix incorrect proc nr_hugepages value 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 Reviewed-by: Naoya Horiguchi Cc: Mike Kravetz Cc: Hillf Danton Cc: Kirill A. Shutemov Cc: Dave Hansen Cc: Paul Gortmaker Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/hugetlb.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'mm/hugetlb.c') diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 06ae13e869d0..01f2b48c8618 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(); -- cgit v1.2.3