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Diffstat (limited to 'Documentation/admin-guide/mm/transhuge.rst')
| -rw-r--r-- | Documentation/admin-guide/mm/transhuge.rst | 37 |
1 files changed, 34 insertions, 3 deletions
diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst index a1bb495eab59..8872203df088 100644 --- a/Documentation/admin-guide/mm/transhuge.rst +++ b/Documentation/admin-guide/mm/transhuge.rst @@ -326,6 +326,29 @@ PMD_ORDER THP policy will be overridden. If the policy for PMD_ORDER is not defined within a valid ``thp_anon``, its policy will default to ``never``. +Similarly to ``transparent_hugepage``, you can control the hugepage +allocation policy for the internal shmem mount by using the kernel parameter +``transparent_hugepage_shmem=<policy>``, where ``<policy>`` is one of the +seven valid policies for shmem (``always``, ``within_size``, ``advise``, +``never``, ``deny``, and ``force``). + +In the same manner as ``thp_anon`` controls each supported anonymous THP +size, ``thp_shmem`` controls each supported shmem THP size. ``thp_shmem`` +has the same format as ``thp_anon``, but also supports the policy +``within_size``. + +``thp_shmem=`` may be specified multiple times to configure all THP sizes +as required. If ``thp_shmem=`` is specified at least once, any shmem THP +sizes not explicitly configured on the command line are implicitly set to +``never``. + +``transparent_hugepage_shmem`` setting only affects the global toggle. If +``thp_shmem`` is not specified, PMD_ORDER hugepage will default to +``inherit``. However, if a valid ``thp_shmem`` setting is provided by the +user, the PMD_ORDER hugepage policy will be overridden. If the policy for +PMD_ORDER is not defined within a valid ``thp_shmem``, its policy will +default to ``never``. + Hugepages in tmpfs/shmem ======================== @@ -413,7 +436,7 @@ AnonHugePmdMapped). The number of file transparent huge pages mapped to userspace is available by reading ShmemPmdMapped and ShmemHugePages fields in ``/proc/meminfo``. To identify what applications are mapping file transparent huge pages, it -is necessary to read ``/proc/PID/smaps`` and count the FileHugeMapped fields +is necessary to read ``/proc/PID/smaps`` and count the FilePmdMapped fields for each mapping. Note that reading the smaps file is expensive and reading it @@ -530,10 +553,18 @@ anon_fault_fallback_charge instead falls back to using huge pages with lower orders or small pages even though the allocation was successful. -swpout - is incremented every time a huge page is swapped out in one +zswpout + is incremented every time a huge page is swapped out to zswap in one piece without splitting. +swpin + is incremented every time a huge page is swapped in from a non-zswap + swap device in one piece. + +swpout + is incremented every time a huge page is swapped out to a non-zswap + swap device in one piece without splitting. + swpout_fallback is incremented if a huge page has to be split before swapout. Usually because failed to allocate some continuous swap space |