docs/vm: hugetlbpage: minor improvements
* fixed mistypes * added internal cross-references for sections Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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@ -87,7 +87,7 @@ memory pressure.
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Once a number of huge pages have been pre-allocated to the kernel huge page
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pool, a user with appropriate privilege can use either the mmap system call
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or shared memory system calls to use the huge pages. See the discussion of
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Using Huge Pages, below.
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:ref:`Using Huge Pages <using_huge_pages>`, below.
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The administrator can allocate persistent huge pages on the kernel boot
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command line by specifying the "hugepages=N" parameter, where 'N' = the
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@ -115,8 +115,9 @@ over all the set of allowed nodes specified by the NUMA memory policy of the
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task that modifies ``nr_hugepages``. The default for the allowed nodes--when the
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task has default memory policy--is all on-line nodes with memory. Allowed
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nodes with insufficient available, contiguous memory for a huge page will be
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silently skipped when allocating persistent huge pages. See the discussion
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below of the interaction of task memory policy, cpusets and per node attributes
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silently skipped when allocating persistent huge pages. See the
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:ref:`discussion below <mem_policy_and_hp_alloc>`
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of the interaction of task memory policy, cpusets and per node attributes
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with the allocation and freeing of persistent huge pages.
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The success or failure of huge page allocation depends on the amount of
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@ -158,7 +159,7 @@ normal page pool.
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Caveat: Shrinking the persistent huge page pool via ``nr_hugepages`` such that
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it becomes less than the number of huge pages in use will convert the balance
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of the in-use huge pages to surplus huge pages. This will occur even if
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the number of surplus pages it would exceed the overcommit value. As long as
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the number of surplus pages would exceed the overcommit value. As long as
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this condition holds--that is, until ``nr_hugepages+nr_overcommit_hugepages`` is
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increased sufficiently, or the surplus huge pages go out of use and are freed--
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no more surplus huge pages will be allowed to be allocated.
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@ -187,6 +188,7 @@ Inside each of these directories, the same set of files will exist::
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which function as described above for the default huge page-sized case.
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.. _mem_policy_and_hp_alloc:
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Interaction of Task Memory Policy with Huge Page Allocation/Freeing
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===================================================================
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@ -282,6 +284,7 @@ Note that the number of overcommit and reserve pages remain global quantities,
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as we don't know until fault time, when the faulting task's mempolicy is
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applied, from which node the huge page allocation will be attempted.
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.. _using_huge_pages:
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Using Huge Pages
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================
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@ -295,7 +298,7 @@ type hugetlbfs::
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min_size=<value>,nr_inodes=<value> none /mnt/huge
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This command mounts a (pseudo) filesystem of type hugetlbfs on the directory
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``/mnt/huge``. Any files created on ``/mnt/huge`` uses huge pages.
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``/mnt/huge``. Any file created on ``/mnt/huge`` uses huge pages.
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The ``uid`` and ``gid`` options sets the owner and group of the root of the
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file system. By default the ``uid`` and ``gid`` of the current process
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@ -345,8 +348,8 @@ applications are going to use only shmat/shmget system calls or mmap with
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MAP_HUGETLB. For an example of how to use mmap with MAP_HUGETLB see
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:ref:`map_hugetlb <map_hugetlb>` below.
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Users who wish to use hugetlb memory via shared memory segment should be a
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member of a supplementary group and system admin needs to configure that gid
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Users who wish to use hugetlb memory via shared memory segment should be
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members of a supplementary group and system admin needs to configure that gid
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into ``/proc/sys/vm/hugetlb_shm_group``. It is possible for same or different
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applications to use any combination of mmaps and shm* calls, though the mount of
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filesystem will be required for using mmap calls without MAP_HUGETLB.
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