madvise(2) - Linux manual page (original) (raw)
madvise(2) System Calls Manual madvise(2)
NAME top
madvise - give advice about use of memoryLIBRARY top
Standard C library (_libc_, _-lc_)SYNOPSIS top
**#include <sys/mman.h>**
**int madvise(void** _addr_**[.**_size_**], size_t** _size_**, int** _advice_**);**Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
**madvise**():
Since glibc 2.19:
_DEFAULT_SOURCE
Up to and including glibc 2.19:
_BSD_SOURCEDESCRIPTION top
The **madvise**() system call is used to give advice or directions to
the kernel about the address range beginning at address _addr_ and
with size _size_. **madvise**() only operates on whole pages, therefore
_addr_ must be page-aligned. The value of _size_ is rounded up to a
multiple of page size. In most cases, the goal of such advice is
to improve system or application performance.
Initially, the system call supported a set of "conventional"
_advice_ values, which are also available on several other
implementations. (Note, though, that **madvise**() is not specified
in POSIX.) Subsequently, a number of Linux-specific _advice_ values
have been added.Conventional advice values The advice values listed below allow an application to tell the kernel how it expects to use some mapped or shared memory areas, so that the kernel can choose appropriate read-ahead and caching techniques. These advice values do not influence the semantics of the application (except in the case of MADV_DONTNEED), but may influence its performance. All of the advice values listed here have analogs in the POSIX-specified posix_madvise(3) function, and the values have the same meanings, with the exception of MADV_DONTNEED.
The advice is indicated in the _advice_ argument, which is one of
the following:
**MADV_NORMAL**
No special treatment. This is the default.
**MADV_RANDOM**
Expect page references in random order. (Hence, read ahead
may be less useful than normally.)
**MADV_SEQUENTIAL**
Expect page references in sequential order. (Hence, pages
in the given range can be aggressively read ahead, and may
be freed soon after they are accessed.)
**MADV_WILLNEED**
Expect access in the near future. (Hence, it might be a
good idea to read some pages ahead.)
**MADV_DONTNEED**
Do not expect access in the near future. (For the time
being, the application is finished with the given range, so
the kernel can free resources associated with it.)
After a successful **MADV_DONTNEED** operation, the semantics
of memory access in the specified region are changed:
subsequent accesses of pages in the range will succeed, but
will result in either repopulating the memory contents from
the up-to-date contents of the underlying mapped file (for
shared file mappings, shared anonymous mappings, and shmem-
based techniques such as System V shared memory segments)
or zero-fill-on-demand pages for anonymous private
mappings.
Note that, when applied to shared mappings, **MADV_DONTNEED**
might not lead to immediate freeing of the pages in the
range. The kernel is free to delay freeing the pages until
an appropriate moment. The resident set size (RSS) of the
calling process will be immediately reduced however.
**MADV_DONTNEED** cannot be applied to locked pages, or
**VM_PFNMAP** pages. (Pages marked with the kernel-internal
**VM_PFNMAP** flag are special memory areas that are not
managed by the virtual memory subsystem. Such pages are
typically created by device drivers that map the pages into
user space.)
Support for Huge TLB pages was added in Linux v5.18.
Addresses within a mapping backed by Huge TLB pages must be
aligned to the underlying Huge TLB page size, and the range
size is rounded up to a multiple of the underlying Huge TLB
page size.Linux-specific advice values The following Linux-specific advice values have no counterparts in the POSIX-specified posix_madvise(3), and may or may not have counterparts in the madvise() interface available on other implementations. Note that some of these operations change the semantics of memory accesses.
**MADV_REMOVE** (since Linux 2.6.16)
Free up a given range of pages and its associated backing
store. This is equivalent to punching a hole in the
corresponding range of the backing store (see
[fallocate(2)](../man2/fallocate.2.html)). Subsequent accesses in the specified
address range will see data with a value of zero.
The specified address range must be mapped shared and
writable. This flag cannot be applied to locked pages, or
**VM_PFNMAP** pages.
In the initial implementation, only [tmpfs(5)](../man5/tmpfs.5.html) supported
**MADV_REMOVE**; but since Linux 3.5, any filesystem which
supports the [fallocate(2)](../man2/fallocate.2.html) **FALLOC_FL_PUNCH_HOLE** mode also
supports **MADV_REMOVE**. Filesystems which do not support
**MADV_REMOVE** fail with the error **EOPNOTSUPP**.
Support for the Huge TLB filesystem was added in Linux
v4.3.
**MADV_DONTFORK** (since Linux 2.6.16)
Do not make the pages in this range available to the child
after a [fork(2)](../man2/fork.2.html). This is useful to prevent copy-on-write
semantics from changing the physical location of a page if
the parent writes to it after a [fork(2)](../man2/fork.2.html). (Such page
relocations cause problems for hardware that DMAs into the
page.)
**MADV_DOFORK** (since Linux 2.6.16)
Undo the effect of **MADV_DONTFORK**, restoring the default
behavior, whereby a mapping is inherited across [fork(2)](../man2/fork.2.html).
**MADV_HWPOISON** (since Linux 2.6.32)
Poison the pages in the range specified by _addr_ and _size_
and handle subsequent references to those pages like a
hardware memory corruption. This operation is available
only for privileged (**CAP_SYS_ADMIN**) processes. This
operation may result in the calling process receiving a
**SIGBUS** and the page being unmapped.
This feature is intended for testing of memory error-
handling code; it is available only if the kernel was
configured with **CONFIG_MEMORY_FAILURE**.
**MADV_MERGEABLE** (since Linux 2.6.32)
Enable Kernel Samepage Merging (KSM) for the pages in the
range specified by _addr_ and _size_. The kernel regularly
scans those areas of user memory that have been marked as
mergeable, looking for pages with identical content. These
are replaced by a single write-protected page (which is
automatically copied if a process later wants to update the
content of the page). KSM merges only private anonymous
pages (see [mmap(2)](../man2/mmap.2.html)).
The KSM feature is intended for applications that generate
many instances of the same data (e.g., virtualization
systems such as KVM). It can consume a lot of processing
power; use with care. See the Linux kernel source file
_Documentation/admin-guide/mm/ksm.rst_ for more details.
The **MADV_MERGEABLE** and **MADV_UNMERGEABLE** operations are
available only if the kernel was configured with
**CONFIG_KSM**.
**MADV_UNMERGEABLE** (since Linux 2.6.32)
Undo the effect of an earlier **MADV_MERGEABLE** operation on
the specified address range; KSM unmerges whatever pages it
had merged in the address range specified by _addr_ and _size_.
**MADV_SOFT_OFFLINE** (since Linux 2.6.33)
Soft offline the pages in the range specified by _addr_ and
_size_. The memory of each page in the specified range is
preserved (i.e., when next accessed, the same content will
be visible, but in a new physical page frame), and the
original page is offlined (i.e., no longer used, and taken
out of normal memory management). The effect of the
**MADV_SOFT_OFFLINE** operation is invisible to (i.e., does not
change the semantics of) the calling process.
This feature is intended for testing of memory error-
handling code; it is available only if the kernel was
configured with **CONFIG_MEMORY_FAILURE**.
**MADV_HUGEPAGE** (since Linux 2.6.38)
Enable Transparent Huge Pages (THP) for pages in the range
specified by _addr_ and _size_. The kernel will regularly scan
the areas marked as huge page candidates to replace them
with huge pages. The kernel will also allocate huge pages
directly when the region is naturally aligned to the huge
page size (see **posix_memalign**(2)).
This feature is primarily aimed at applications that use
large mappings of data and access large regions of that
memory at a time (e.g., virtualization systems such as
QEMU). It can very easily waste memory (e.g., a 2 MB
mapping that only ever accesses 1 byte will result in 2 MB
of wired memory instead of one 4 KB page). See the Linux
kernel source file
_Documentation/admin-guide/mm/transhuge.rst_ for more
details.
Most common kernels configurations provide **MADV_HUGEPAGE**-
style behavior by default, and thus **MADV_HUGEPAGE** is
normally not necessary. It is mostly intended for embedded
systems, where **MADV_HUGEPAGE**-style behavior may not be
enabled by default in the kernel. On such systems, this
flag can be used in order to selectively enable THP.
Whenever **MADV_HUGEPAGE** is used, it should always be in
regions of memory with an access pattern that the developer
knows in advance won't risk to increase the memory
footprint of the application when transparent hugepages are
enabled.
Since Linux 5.4, automatic scan of eligible areas and
replacement by huge pages works with private anonymous
pages (see [mmap(2)](../man2/mmap.2.html)), shmem pages, and file-backed pages.
For all memory types, memory may only be replaced by huge
pages on hugepage-aligned boundaries. For file-mapped
memory —including tmpfs (see **tmpfs**(2))— the mapping must
also be naturally hugepage-aligned within the file.
Additionally, for file-backed, non-tmpfs memory, the file
must not be open for write and the mapping must be
executable.
The VMA must not be marked **VM_NOHUGEPAGE**, **VM_HUGETLB**,
**VM_IO**, **VM_DONTEXPAND**, **VM_MIXEDMAP**, or **VM_PFNMAP**, nor can it
be stack memory or backed by a DAX-enabled device (unless
the DAX device is hot-plugged as System RAM). The process
must also not have **PR_SET_THP_DISABLE** set (see [prctl(2)](../man2/prctl.2.html)).
The **MADV_HUGEPAGE**, **MADV_NOHUGEPAGE**, and **MADV_COLLAPSE**
operations are available only if the kernel was configured
with **CONFIG_TRANSPARENT_HUGEPAGE** and file/shmem memory is
only supported if the kernel was configured with
**CONFIG_READ_ONLY_THP_FOR_FS**.
**MADV_NOHUGEPAGE** (since Linux 2.6.38)
Ensures that memory in the address range specified by _addr_
and _size_ will not be backed by transparent hugepages.
**MADV_COLLAPSE** (since Linux 6.1)
Perform a best-effort synchronous collapse of the native
pages mapped by the memory range into Transparent Huge
Pages (THPs). **MADV_COLLAPSE** operates on the current state
of memory of the calling process and makes no persistent
changes or guarantees on how pages will be mapped,
constructed, or faulted in the future.
**MADV_COLLAPSE** supports private anonymous pages (see
[mmap(2)](../man2/mmap.2.html)), shmem pages, and file-backed pages. See
**MADV_HUGEPAGE** for general information on memory
requirements for THP. If the range provided spans multiple
VMAs, the semantics of the collapse over each VMA is
independent from the others. If collapse of a given huge
page-aligned/sized region fails, the operation may continue
to attempt collapsing the remainder of the specified
memory. **MADV_COLLAPSE** will automatically clamp the
provided range to be hugepage-aligned.
All non-resident pages covered by the range will first be
swapped/faulted-in, before being copied onto a freshly
allocated hugepage. If the native pages compose the same
PTE-mapped hugepage, and are suitably aligned, allocation
of a new hugepage may be elided and collapse may happen in-
place. Unmapped pages will have their data directly
initialized to 0 in the new hugepage. However, for every
eligible hugepage-aligned/sized region to be collapsed, at
least one page must currently be backed by physical memory.
**MADV_COLLAPSE** is independent of any sysfs (see [sysfs(5)](../man5/sysfs.5.html))
setting under _/sys/kernel/mm/transparenthugepage_, both in
terms of determining THP eligibility, and allocation
semantics. See Linux kernel source file
_Documentation/admin-guide/mm/transhuge.rst_ for more
information. **MADV_COLLAPSE** also ignores **huge=** tmpfs mount
when operating on tmpfs files. Allocation for the new
hugepage may enter direct reclaim and/or compaction,
regardless of VMA flags (though **VM_NOHUGEPAGE** is still
respected).
When the system has multiple NUMA nodes, the hugepage will
be allocated from the node providing the most native pages.
If all hugepage-sized/aligned regions covered by the
provided range were either successfully collapsed, or were
already PMD-mapped THPs, this operation will be deemed
successful. Note that this doesn't guarantee anything
about other possible mappings of the memory. In the event
multiple hugepage-aligned/sized areas fail to collapse,
only the most-recently–failed code will be set in _[errno](../man3/errno.3.html)_.
**MADV_DONTDUMP** (since Linux 3.4)
Exclude from a core dump those pages in the range specified
by _addr_ and _size_. This is useful in applications that have
large areas of memory that are known not to be useful in a
core dump. The effect of **MADV_DONTDUMP** takes precedence
over the bit mask that is set via the
_/proc/_pid_/coredumpfilter_ file (see [core(5)](../man5/core.5.html)).
**MADV_DODUMP** (since Linux 3.4)
Undo the effect of an earlier **MADV_DONTDUMP**.
**MADV_FREE** (since Linux 4.5)
The application no longer requires the pages in the range
specified by _addr_ and _size_. The kernel can thus free these
pages, but the freeing could be delayed until memory
pressure occurs. For each of the pages that has been
marked to be freed but has not yet been freed, the free
operation will be canceled if the caller writes into the
page. After a successful **MADV_FREE** operation, any stale
data (i.e., dirty, unwritten pages) will be lost when the
kernel frees the pages. However, subsequent writes to
pages in the range will succeed and then kernel cannot free
those dirtied pages, so that the caller can always see just
written data. If there is no subsequent write, the kernel
can free the pages at any time. Once pages in the range
have been freed, the caller will see zero-fill-on-demand
pages upon subsequent page references.
The **MADV_FREE** operation can be applied only to private
anonymous pages (see [mmap(2)](../man2/mmap.2.html)). Before Linux 4.12, when
freeing pages on a swapless system, the pages in the given
range are freed instantly, regardless of memory pressure.
**MADV_WIPEONFORK** (since Linux 4.14)
Present the child process with zero-filled memory in this
range after a [fork(2)](../man2/fork.2.html). This is useful in forking servers
in order to ensure that sensitive per-process data (for
example, PRNG seeds, cryptographic secrets, and so on) is
not handed to child processes.
The **MADV_WIPEONFORK** operation can be applied only to
private anonymous pages (see [mmap(2)](../man2/mmap.2.html)).
Within the child created by [fork(2)](../man2/fork.2.html), the **MADV_WIPEONFORK**
setting remains in place on the specified address range.
This setting is cleared during [execve(2)](../man2/execve.2.html).
**MADV_KEEPONFORK** (since Linux 4.14)
Undo the effect of an earlier **MADV_WIPEONFORK**.
**MADV_COLD** (since Linux 5.4)
Deactivate a given range of pages. This will make the
pages a more probable reclaim target should there be a
memory pressure. This is a nondestructive operation. The
advice might be ignored for some pages in the range when it
is not applicable.
**MADV_PAGEOUT** (since Linux 5.4)
Reclaim a given range of pages. This is done to free up
memory occupied by these pages. If a page is anonymous, it
will be swapped out. If a page is file-backed and dirty,
it will be written back to the backing storage. The advice
might be ignored for some pages in the range when it is not
applicable.
**MADV_POPULATE_READ** (since Linux 5.14)
"Populate (prefault) page tables readable, faulting in all
pages in the range just as if manually reading from each
page; however, avoid the actual memory access that would
have been performed after handling the fault.
In contrast to **MAP_POPULATE**, **MADV_POPULATE_READ** does not
hide errors, can be applied to (parts of) existing mappings
and will always populate (prefault) page tables readable.
One example use case is prefaulting a file mapping, reading
all file content from disk; however, pages won't be dirtied
and consequently won't have to be written back to disk when
evicting the pages from memory.
Depending on the underlying mapping, map the shared
zeropage, preallocate memory or read the underlying file;
files with holes might or might not preallocate blocks. If
populating fails, a **SIGBUS** signal is not generated;
instead, an error is returned.
If **MADV_POPULATE_READ** succeeds, all page tables have been
populated (prefaulted) readable once. If
**MADV_POPULATE_READ** fails, some page tables might have been
populated.
**MADV_POPULATE_READ** cannot be applied to mappings without
read permissions and special mappings, for example,
mappings marked with kernel-internal flags such as
**VM_PFNMAP** or **VM_IO**, or secret memory regions created using
[memfd_secret(2)](../man2/memfd%5Fsecret.2.html).
Note that with **MADV_POPULATE_READ**, the process can be
killed at any moment when the system runs out of memory.
**MADV_POPULATE_WRITE** (since Linux 5.14)
Populate (prefault) page tables writable, faulting in all
pages in the range just as if manually writing to each each
page; however, avoid the actual memory access that would
have been performed after handling the fault.
In contrast to **MAP_POPULATE**, MADV_POPULATE_WRITE does not
hide errors, can be applied to (parts of) existing mappings
and will always populate (prefault) page tables writable.
One example use case is preallocating memory, breaking any
CoW (Copy on Write).
Depending on the underlying mapping, preallocate memory or
read the underlying file; files with holes will preallocate
blocks. If populating fails, a **SIGBUS** signal is not
generated; instead, an error is returned.
If **MADV_POPULATE_WRITE** succeeds, all page tables have been
populated (prefaulted) writable once. If
**MADV_POPULATE_WRITE** fails, some page tables might have been
populated.
**MADV_POPULATE_WRITE** cannot be applied to mappings without
write permissions and special mappings, for example,
mappings marked with kernel-internal flags such as
**VM_PFNMAP** or **VM_IO**, or secret memory regions created using
[memfd_secret(2)](../man2/memfd%5Fsecret.2.html).
Note that with **MADV_POPULATE_WRITE**, the process can be
killed at any moment when the system runs out of memory.
**MADV_GUARD_INSTALL** (since Linux 6.13)
Install a lightweight guard region into the range specified
by _addr_ and _size_, causing any read or write in the range to
result in a **SIGSEGV** signal being raised.
If the region maps memory pages those mappings will be
replaced as part of the operation, though if
**MADV_GUARD_INSTALL** is applied to regions containing pre-
existing lightweight guard regions, they are left in place.
This operation is supported only for writable anonymous
private mappings which have not been mlock'd. An **EINVAL**
error is returned if it is attempted on any other kind of
mapping.
This operation is more efficient than mapping a new region
of memory **PROT_NONE**, as it does not require the
establishment of new mappings. Instead, regions of an
existing mapping simply have their page tables manipulated
to establish the desired behavior. No additional memory is
used.
Lightweight guard regions remain on fork (except for any
parts which have had **MADV_WIPEONFORK** applied to them), and
are not removed by **MADV_DONTNEED**, **MADV_FREE**, **MADV_PAGEOUT**,
or **MADV_COLD**.
Attempting to [mlock(2)](../man2/mlock.2.html) lightweight guard regions will fail,
as will **MADV_POPULATE_READ** or **MADV_POPULATE_WRITE**.
If the mapping has its attributes changed, or is split or
partially unmapped, any existing guard regions remain in
place (except if they are unmapped).
If a mapping is moved using [mremap(2)](../man2/mremap.2.html), lightweight guard
regions are moved with it.
Lightweight guard regions are removed when unmapped, on
process teardown, or when the **MADV_GUARD_REMOVE** operation
is applied to them.
**MADV_GUARD_REMOVE** (since Linux 6.13)
Remove any lightweight guard regions which exist in the
range specified by _addr_ and _size_.
All mappings in the range other than lightweight guard
regions are left in place (including mlock'd mappings).
The operation is, however, valid only for writable
anonymous private mappings, returning an **EINVAL** error
otherwise.
When lightweight guard regions are removed, they act as
empty regions of the containing mapping. Since only
writable anonymous private mappings are supported, they
therefore become zero-fill-on-demand pages.
If any transparent huge pages are encountered in the
operation, they are left in place.RETURN VALUE top
On success, **madvise**() returns zero. On error, it returns -1 and
_[errno](../man3/errno.3.html)_ is set to indicate the error.ERRORS top
**EACCES** _advice_ is **MADV_REMOVE**, but the specified address range is
not a shared writable mapping.
**EAGAIN** A kernel resource was temporarily unavailable.
**EBADF** The map exists, but the area maps something that isn't a
file.
**EBUSY** (for **MADV_COLLAPSE**) Could not charge hugepage to cgroup:
cgroup limit exceeded.
**EBUSY** (for **MADV_SOFT_OFFLINE**) Any pages within the specified
address range could not be offlined. This might occur if
the page is currently in use or locked.
**EFAULT** _advice_ is **MADV_POPULATE_READ** or **MADV_POPULATE_WRITE**, and
populating (prefaulting) page tables failed because a
**SIGBUS** would have been generated on actual memory access
and the reason is not a HW poisoned page (HW poisoned pages
can, for example, be created using the **MADV_HWPOISON** flag
described elsewhere in this page).
**EINVAL** _addr_ is not page-aligned or _size_ is negative.
**EINVAL** _advice_ is not a valid.
**EINVAL** _advice_ is **MADV_COLD** or **MADV_PAGEOUT** and the specified
address range includes locked, Huge TLB pages, or **VM_PFNMAP**
pages.
**EINVAL** _advice_ is **MADV_DONTNEED** or **MADV_REMOVE** and the specified
address range includes locked, Huge TLB pages, or **VM_PFNMAP**
pages.
**EINVAL** _advice_ is **MADV_MERGEABLE** or **MADV_UNMERGEABLE**, but the
kernel was not configured with **CONFIG_KSM**.
**EINVAL** _advice_ is **MADV_FREE** or **MADV_WIPEONFORK** but the specified
address range includes file, Huge TLB, **MAP_SHARED**, or
**VM_PFNMAP** ranges.
**EINVAL** _advice_ is **MADV_POPULATE_READ** or **MADV_POPULATE_WRITE**, but
the specified address range includes ranges with
insufficient permissions or special mappings, for example,
mappings marked with kernel-internal flags such a **VM_IO** or
**VM_PFNMAP**, or secret memory regions created using
[memfd_secret(2)](../man2/memfd%5Fsecret.2.html).
**EINVAL** _advice_ is **MADV_GUARD_INSTALL** or **MADV_GUARD_REMOVE**, but the
specified address range contains an unsupported mapping.
**EIO** (for **MADV_WILLNEED**) Paging in this area would exceed the
process's maximum resident set size.
**ENOMEM** (for **MADV_WILLNEED**) Not enough memory: paging in failed.
**ENOMEM** (for **MADV_COLLAPSE**) Not enough memory: could not allocate
hugepage.
**ENOMEM** Addresses in the specified range are not currently mapped,
or are outside the address space of the process.
**ENOMEM** _advice_ is **MADV_POPULATE_READ** or **MADV_POPULATE_WRITE**, and
populating (prefaulting) page tables failed because there
was not enough memory.
**EPERM** _advice_ is **MADV_HWPOISON**, but the caller does not have the
**CAP_SYS_ADMIN** capability.
**EHWPOISON**
_advice_ is **MADV_POPULATE_READ** or **MADV_POPULATE_WRITE**, and
populating (prefaulting) page tables failed because a HW
poisoned page (HW poisoned pages can, for example, be
created using the **MADV_HWPOISON** flag described elsewhere in
this page) was encountered.VERSIONS top
Versions of this system call, implementing a wide variety of
_advice_ values, exist on many other implementations. Other
implementations typically implement at least the flags listed
above under _Conventional advice flags_, albeit with some variation
in semantics.
POSIX.1-2001 describes [posix_madvise(3)](../man3/posix%5Fmadvise.3.html) with constants
**POSIX_MADV_NORMAL**, **POSIX_MADV_RANDOM**, **POSIX_MADV_SEQUENTIAL**,
**POSIX_MADV_WILLNEED**, and **POSIX_MADV_DONTNEED**, and so on, with
behavior close to the similarly named flags listed above.Linux The Linux implementation requires that the address addr be page- aligned, and allows size to be zero. If there are some parts of the specified address range that are not mapped, the Linux version of madvise() ignores them and applies the call to the rest (but returns ENOMEM from the system call, as it should).
_madvise(0, 0, advice)_ will return zero iff _advice_ is supported by
the kernel and can be relied on to probe for support.STANDARDS top
None.HISTORY top
First appeared in 4.4BSD.
Since Linux 3.18, support for this system call is optional,
depending on the setting of the **CONFIG_ADVISE_SYSCALLS**
configuration option.SEE ALSO top
[getrlimit(2)](../man2/getrlimit.2.html), [memfd_secret(2)](../man2/memfd%5Fsecret.2.html), [mincore(2)](../man2/mincore.2.html), [mmap(2)](../man2/mmap.2.html), [mprotect(2)](../man2/mprotect.2.html),
[msync(2)](../man2/msync.2.html), [munmap(2)](../man2/munmap.2.html), [prctl(2)](../man2/prctl.2.html), [process_madvise(2)](../man2/process%5Fmadvise.2.html),
[posix_madvise(3)](../man3/posix%5Fmadvise.3.html), [core(5)](../man5/core.5.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-12-23 madvise(2)
Pages that refer to this page:fork(2), getrlimit(2), io_uring_enter2(2), io_uring_enter(2), mincore(2), open(2), process_madvise(2), PR_SET_THP_DISABLE(2const), readahead(2), syscalls(2), UFFDIO_API(2const), userfaultfd(2), io_uring_prep_madvise(3), io_uring_prep_madvise64(3), malloc_trim(3), posix_madvise(3), core(5), proc_meminfo(5), tmpfs(5), capabilities(7)