Messages in this thread Patch in this message | | | From | Vaishali Thakkar <> | Subject | [PATCH] mm/hugetlb: Fix incorrect proc nr_hugepages value | Date | Wed, 17 Feb 2016 01:13:26 +0530 |
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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> --- 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
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