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 	during boot. This parameter can be used to improve system bootup time
158 	Note that this parameter only applies to non-gigantic huge pages.
160 	Specify the default huge page size.  This parameter can
162 	optionally be followed by the hugepages parameter to preallocate a
179 indicates the current number of pre-allocated huge pages of the default size.
190 task that modifies ``nr_hugepages``. The default for the allowed nodes--when the
191 task has default memory policy--is all on-line nodes with memory.  Allowed
216 requested by applications.  Writing any non-zero value into this file
235 it becomes less than the number of huge pages in use will convert the balance
236 of the in-use huge pages to surplus huge pages.  This will occur even if
238 this condition holds--that is, until ``nr_hugepages+nr_overcommit_hugepages`` is
239 increased sufficiently, or the surplus huge pages go out of use and are freed--
242 With support for multiple huge page pools at run-time available, much of
253 	hugepages-${size}kB
279         these smaller sizes.  Only huge page sizes less than the current huge
290 demote_size) function as described above for the default huge page-sized case.
307     numactl --interleave <node-list> echo 20 \
312     numactl -m <node-list> echo 20 >/proc/sys/vm/nr_hugepages_mempolicy
314 This will allocate or free ``abs(20 - nr_hugepages)`` to or from the nodes
315 specified in <node-list>, depending on whether number of persistent huge pages
316 is initially less than or greater than 20, respectively.  No huge pages will be
317 allocated nor freed on any node not included in the specified <node-list>.
320 memory policy mode--bind, preferred, local or interleave--may be used.  The
324    Documentation/admin-guide/mm/numa_memory_policy.rst],
344 #. The nodes allowed mask will be derived from any non-default task mempolicy,
347    shell with non-default policy, that policy will be used.  One can specify a
348    node list of "all" with numactl --interleave or --membind [-m] to achieve
351 #. Any task mempolicy specified--e.g., using numactl--will be constrained by
353    be no way for a task with non-default policy running in a cpuset with a
357 #. Boot-time huge page allocation attempts to distribute the requested number
358    of huge pages over all on-lines nodes with memory.
367 	/sys/devices/system/node/node[0-9]*/hugepages/
376 The free\_' and surplus\_' attribute files are read-only.  They return the number
389 The hugetlb may be migrated between the per-node hugepages pool in the following
394 hugetlb migration, that means these 3 cases can break the per-node hugepages pool.
405   mount -t hugetlbfs \
406 	-o uid=<value>,gid=<value>,mode=<value>,pagesize=<value>,size=<value>,\
481 ``hugepage-shm``
482 	see tools/testing/selftests/mm/hugepage-shm.c
484 ``hugepage-mmap``
485 	see tools/testing/selftests/mm/hugepage-mmap.c