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    mm/hugetlb.c: fix incorrect proc nr_hugepages value · f8b74815
    Vaishali Thakkar 提交于
    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: NVaishali Thakkar <vaishali.thakkar@oracle.com>
    Reviewed-by: NNaoya 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: NAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
    f8b74815
hugetlb.c 117.9 KB