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authorVaishali Thakkar <vaishali.thakkar@oracle.com>2016-02-17 13:11:26 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2016-02-18 16:23:24 -0800
commitf8b74815a452ff2904b5d7fcce1a5ae2a4d7ca5e (patch)
parent457a98b0809fa6cde7aab8c314a59d99772b445e (diff)
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 <vaishali.thakkar@oracle.com> Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 files changed, 4 insertions, 2 deletions
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)
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;
+ }