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authorLinus Torvalds <torvalds@linux-foundation.org>2021-07-02 22:08:10 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2021-07-02 22:08:10 +0300
commit71bd9341011f626d692aabe024f099820f02c497 (patch)
treea1c27fd8f17daff36e380800c5b69769d0d9cc99 /Documentation/admin-guide
parent3dbdb38e286903ec220aaf1fb29a8d94297da246 (diff)
parentb869d5be0acf0e125e69adcffdca04000dc5b17c (diff)
downloadlinux-71bd9341011f626d692aabe024f099820f02c497.tar.xz
Merge branch 'akpm' (patches from Andrew)
Merge more updates from Andrew Morton: "190 patches. Subsystems affected by this patch series: mm (hugetlb, userfaultfd, vmscan, kconfig, proc, z3fold, zbud, ras, mempolicy, memblock, migration, thp, nommu, kconfig, madvise, memory-hotplug, zswap, zsmalloc, zram, cleanups, kfence, and hmm), procfs, sysctl, misc, core-kernel, lib, lz4, checkpatch, init, kprobes, nilfs2, hfs, signals, exec, kcov, selftests, compress/decompress, and ipc" * emailed patches from Andrew Morton <akpm@linux-foundation.org>: (190 commits) ipc/util.c: use binary search for max_idx ipc/sem.c: use READ_ONCE()/WRITE_ONCE() for use_global_lock ipc: use kmalloc for msg_queue and shmid_kernel ipc sem: use kvmalloc for sem_undo allocation lib/decompressors: remove set but not used variabled 'level' selftests/vm/pkeys: exercise x86 XSAVE init state selftests/vm/pkeys: refill shadow register after implicit kernel write selftests/vm/pkeys: handle negative sys_pkey_alloc() return code selftests/vm/pkeys: fix alloc_random_pkey() to make it really, really random kcov: add __no_sanitize_coverage to fix noinstr for all architectures exec: remove checks in __register_bimfmt() x86: signal: don't do sas_ss_reset() until we are certain that sigframe won't be abandoned hfsplus: report create_date to kstat.btime hfsplus: remove unnecessary oom message nilfs2: remove redundant continue statement in a while-loop kprobes: remove duplicated strong free_insn_page in x86 and s390 init: print out unknown kernel parameters checkpatch: do not complain about positive return values starting with EPOLL checkpatch: improve the indented label test checkpatch: scripts/spdxcheck.py now requires python3 ...
Diffstat (limited to 'Documentation/admin-guide')
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt21
-rw-r--r--Documentation/admin-guide/mm/hugetlbpage.rst11
-rw-r--r--Documentation/admin-guide/mm/memory-hotplug.rst13
-rw-r--r--Documentation/admin-guide/mm/pagemap.rst2
-rw-r--r--Documentation/admin-guide/mm/userfaultfd.rst3
5 files changed, 49 insertions, 1 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 0315407f5f57..13f13fdd4731 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1594,6 +1594,23 @@
Documentation/admin-guide/mm/hugetlbpage.rst.
Format: size[KMG]
+ hugetlb_free_vmemmap=
+ [KNL] Reguires CONFIG_HUGETLB_PAGE_FREE_VMEMMAP
+ enabled.
+ Allows heavy hugetlb users to free up some more
+ memory (6 * PAGE_SIZE for each 2MB hugetlb page).
+ Format: { on | off (default) }
+
+ on: enable the feature
+ off: disable the feature
+
+ Built with CONFIG_HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON=y,
+ the default is on.
+
+ This is not compatible with memory_hotplug.memmap_on_memory.
+ If both parameters are enabled, hugetlb_free_vmemmap takes
+ precedence over memory_hotplug.memmap_on_memory.
+
hung_task_panic=
[KNL] Should the hung task detector generate panics.
Format: 0 | 1
@@ -2860,6 +2877,10 @@
Note that even when enabled, there are a few cases where
the feature is not effective.
+ This is not compatible with hugetlb_free_vmemmap. If
+ both parameters are enabled, hugetlb_free_vmemmap takes
+ precedence over memory_hotplug.memmap_on_memory.
+
memtest= [KNL,X86,ARM,PPC,RISCV] Enable memtest
Format: <integer>
default : 0 <disable>
diff --git a/Documentation/admin-guide/mm/hugetlbpage.rst b/Documentation/admin-guide/mm/hugetlbpage.rst
index f7b1c7462991..8abaeb144e44 100644
--- a/Documentation/admin-guide/mm/hugetlbpage.rst
+++ b/Documentation/admin-guide/mm/hugetlbpage.rst
@@ -60,6 +60,10 @@ HugePages_Surp
the pool above the value in ``/proc/sys/vm/nr_hugepages``. The
maximum number of surplus huge pages is controlled by
``/proc/sys/vm/nr_overcommit_hugepages``.
+ Note: When the feature of freeing unused vmemmap pages associated
+ with each hugetlb page is enabled, the number of surplus huge pages
+ may be temporarily larger than the maximum number of surplus huge
+ pages when the system is under memory pressure.
Hugepagesize
is the default hugepage size (in Kb).
Hugetlb
@@ -80,6 +84,10 @@ returned to the huge page pool when freed by a task. A user with root
privileges can dynamically allocate more or free some persistent huge pages
by increasing or decreasing the value of ``nr_hugepages``.
+Note: When the feature of freeing unused vmemmap pages associated with each
+hugetlb page is enabled, we can fail to free the huge pages triggered by
+the user when ths system is under memory pressure. Please try again later.
+
Pages that are used as huge pages are reserved inside the kernel and cannot
be used for other purposes. Huge pages cannot be swapped out under
memory pressure.
@@ -145,6 +153,9 @@ default_hugepagesz
will all result in 256 2M huge pages being allocated. Valid default
huge page size is architecture dependent.
+hugetlb_free_vmemmap
+ When CONFIG_HUGETLB_PAGE_FREE_VMEMMAP is set, this enables freeing
+ unused vmemmap pages associated with each HugeTLB page.
When multiple huge page sizes are supported, ``/proc/sys/vm/nr_hugepages``
indicates the current number of pre-allocated huge pages of the default size.
diff --git a/Documentation/admin-guide/mm/memory-hotplug.rst b/Documentation/admin-guide/mm/memory-hotplug.rst
index 05d51d2d8beb..c6bae2d77160 100644
--- a/Documentation/admin-guide/mm/memory-hotplug.rst
+++ b/Documentation/admin-guide/mm/memory-hotplug.rst
@@ -357,6 +357,19 @@ creates ZONE_MOVABLE as following.
Unfortunately, there is no information to show which memory block belongs
to ZONE_MOVABLE. This is TBD.
+ Memory offlining can fail when dissolving a free huge page on ZONE_MOVABLE
+ and the feature of freeing unused vmemmap pages associated with each hugetlb
+ page is enabled.
+
+ This can happen when we have plenty of ZONE_MOVABLE memory, but not enough
+ kernel memory to allocate vmemmmap pages. We may even be able to migrate
+ huge page contents, but will not be able to dissolve the source huge page.
+ This will prevent an offline operation and is unfortunate as memory offlining
+ is expected to succeed on movable zones. Users that depend on memory hotplug
+ to succeed for movable zones should carefully consider whether the memory
+ savings gained from this feature are worth the risk of possibly not being
+ able to offline memory in certain situations.
+
.. note::
Techniques that rely on long-term pinnings of memory (especially, RDMA and
vfio) are fundamentally problematic with ZONE_MOVABLE and, therefore, memory
diff --git a/Documentation/admin-guide/mm/pagemap.rst b/Documentation/admin-guide/mm/pagemap.rst
index 340a5aee9b80..fb578fbbb76c 100644
--- a/Documentation/admin-guide/mm/pagemap.rst
+++ b/Documentation/admin-guide/mm/pagemap.rst
@@ -21,6 +21,8 @@ There are four components to pagemap:
* Bit 55 pte is soft-dirty (see
:ref:`Documentation/admin-guide/mm/soft-dirty.rst <soft_dirty>`)
* Bit 56 page exclusively mapped (since 4.2)
+ * Bit 57 pte is uffd-wp write-protected (since 5.13) (see
+ :ref:`Documentation/admin-guide/mm/userfaultfd.rst <userfaultfd>`)
* Bits 57-60 zero
* Bit 61 page is file-page or shared-anon (since 3.5)
* Bit 62 page swapped
diff --git a/Documentation/admin-guide/mm/userfaultfd.rst b/Documentation/admin-guide/mm/userfaultfd.rst
index 3aa38e8b8361..6528036093e1 100644
--- a/Documentation/admin-guide/mm/userfaultfd.rst
+++ b/Documentation/admin-guide/mm/userfaultfd.rst
@@ -77,7 +77,8 @@ events, except page fault notifications, may be generated:
- ``UFFD_FEATURE_MINOR_HUGETLBFS`` indicates that the kernel supports
``UFFDIO_REGISTER_MODE_MINOR`` registration for hugetlbfs virtual memory
- areas.
+ areas. ``UFFD_FEATURE_MINOR_SHMEM`` is the analogous feature indicating
+ support for shmem virtual memory areas.
The userland application should set the feature flags it intends to use
when invoking the ``UFFDIO_API`` ioctl, to request that those features be