admin-guide/mm/hugetlbpage.rst

13 256M and ppc64 supports 4K and 16M.  A TLB is a cache of virtual-to-physical
93 Once a number of huge pages have been pre-allocated to the kernel huge page
99 command line by specifying the "hugepages=N" parameter, where 'N' = the
105 with a huge page size selection parameter "hugepagesz=<size>".  <size> must
107 page size may be selected with the "default_hugepagesz=<size>" boot parameter.
109 Hugetlb boot command line parameter semantics
113 	parameter to preallocate a number of huge pages of the specified
124 	follows a valid hugepagesz or default_hugepagesz parameter.  However,
125 	if hugepages is the first or only hugetlb command line parameter it
129 	parameter pair for the default size.  This parameter also has a
138 	indicating that the hugepages=512 parameter is ignored.  If a hugepages
139 	parameter is preceded by an invalid hugepagesz parameter, it will
147 	If the node number is invalid,  the parameter will be ignored.
150 	Specify the default huge page size.  This parameter can
152 	optionally be followed by the hugepages parameter to preallocate a
169 indicates the current number of pre-allocated huge pages of the default size.
180 task that modifies ``nr_hugepages``. The default for the allowed nodes--when the
181 task has default memory policy--is all on-line nodes with memory.  Allowed
206 requested by applications.  Writing any non-zero value into this file
225 it becomes less than the number of huge pages in use will convert the balance
226 of the in-use huge pages to surplus huge pages.  This will occur even if
228 this condition holds--that is, until ``nr_hugepages+nr_overcommit_hugepages`` is
229 increased sufficiently, or the surplus huge pages go out of use and are freed--
232 With support for multiple huge page pools at run-time available, much of
243 	hugepages-${size}kB
269         these smaller sizes.  Only huge page sizes less than the current huge
280 demote_size) function as described above for the default huge page-sized case.
297     numactl --interleave <node-list> echo 20 \
302     numactl -m <node-list> echo 20 >/proc/sys/vm/nr_hugepages_mempolicy
304 This will allocate or free ``abs(20 - nr_hugepages)`` to or from the nodes
305 specified in <node-list>, depending on whether number of persistent huge pages
306 is initially less than or greater than 20, respectively.  No huge pages will be
307 allocated nor freed on any node not included in the specified <node-list>.
310 memory policy mode--bind, preferred, local or interleave--may be used.  The
314    Documentation/admin-guide/mm/numa_memory_policy.rst],
334 #. The nodes allowed mask will be derived from any non-default task mempolicy,
337    shell with non-default policy, that policy will be used.  One can specify a
338    node list of "all" with numactl --interleave or --membind [-m] to achieve
341 #. Any task mempolicy specified--e.g., using numactl--will be constrained by
343    be no way for a task with non-default policy running in a cpuset with a
347 #. Boot-time huge page allocation attempts to distribute the requested number
348    of huge pages over all on-lines nodes with memory.
357 	/sys/devices/system/node/node[0-9]*/hugepages/
366 The free\_' and surplus\_' attribute files are read-only.  They return the number
379 The hugetlb may be migrated between the per-node hugepages pool in the following
384 hugetlb migration, that means these 3 cases can break the per-node hugepages pool.
395   mount -t hugetlbfs \
396 	-o uid=<value>,gid=<value>,mode=<value>,pagesize=<value>,size=<value>,\
471 ``hugepage-shm``
472 	see tools/testing/selftests/mm/hugepage-shm.c
474 ``hugepage-mmap``
475 	see tools/testing/selftests/mm/hugepage-mmap.c