mm: override mTHP "enabled" defaults at kernel cmdline

Add thp_anon= cmdline parameter to allow specifying the default enablement
of each supported anon THP size.  The parameter accepts the following
format and can be provided multiple times to configure each size:

thp_anon=<size>,<size>[KMG]:<value>;<size>-<size>[KMG]:<value>

An example:

thp_anon=16K-64K:always;128K,512K:inherit;256K:madvise;1M-2M:never

See Documentation/admin-guide/mm/transhuge.rst for more details.

Configuring the defaults at boot time is useful to allow early user space
to take advantage of mTHP before its been configured through sysfs.

[[email protected]: use get_oder() and check size is is_power_of_2]
  Link: https://lkml.kernel.org/r/[email protected]
[[email protected]: some minor cleanup according to David's comments]
  Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ryan Roberts <[email protected]>
Co-developed-by: Barry Song <[email protected]>
Signed-off-by: Barry Song <[email protected]>
Reviewed-by: Baolin Wang <[email protected]>
Tested-by: Baolin Wang <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Lance Yang <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions