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diff --git a/man2/madvise.2 b/man2/madvise.2 deleted file mode 100644 index c30ec4c..0000000 --- a/man2/madvise.2 +++ /dev/null @@ -1,898 +0,0 @@ -.\" Copyright (C) 2001 David Gómez <davidge@jazzfree.com> -.\" -.\" SPDX-License-Identifier: Linux-man-pages-copyleft -.\" -.\" Based on comments from mm/filemap.c. Last modified on 10-06-2001 -.\" Modified, 25 Feb 2002, Michael Kerrisk, <mtk.manpages@gmail.com> -.\" Added notes on MADV_DONTNEED -.\" 2010-06-19, mtk, Added documentation of MADV_MERGEABLE and -.\" MADV_UNMERGEABLE -.\" 2010-06-15, Andi Kleen, Add documentation of MADV_HWPOISON. -.\" 2010-06-19, Andi Kleen, Add documentation of MADV_SOFT_OFFLINE. -.\" 2011-09-18, Doug Goldstein <cardoe@cardoe.com> -.\" Document MADV_HUGEPAGE and MADV_NOHUGEPAGE -.\" -.TH madvise 2 2023-10-31 "Linux man-pages 6.7" -.SH NAME -madvise \- give advice about use of memory -.SH LIBRARY -Standard C library -.RI ( libc ", " \-lc ) -.SH SYNOPSIS -.nf -.B #include <sys/mman.h> -.P -.BI "int madvise(void " addr [. length "], size_t " length ", int " advice ); -.fi -.P -.RS -4 -Feature Test Macro Requirements for glibc (see -.BR feature_test_macros (7)): -.RE -.P -.BR madvise (): -.nf - Since glibc 2.19: - _DEFAULT_SOURCE - Up to and including glibc 2.19: - _BSD_SOURCE -.fi -.SH DESCRIPTION -The -.BR madvise () -system call is used to give advice or directions to the kernel -about the address range beginning at address -.I addr -and with size -.IR length . -.BR madvise () -only operates on whole pages, therefore -.I addr -must be page-aligned. -The value of -.I length -is rounded up to a multiple of page size. -In most cases, -the goal of such advice is to improve system or application performance. -.P -Initially, the system call supported a set of "conventional" -.I advice -values, which are also available on several other implementations. -(Note, though, that -.BR madvise () -is not specified in POSIX.) -Subsequently, a number of Linux-specific -.I advice -values have been added. -.\" -.\" ====================================================================== -.\" -.SS Conventional advice values -The -.I 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 -.I advice -values do not influence the semantics of the application -(except in the case of -.BR MADV_DONTNEED ), -but may influence its performance. -All of the -.I advice -values listed here have analogs in the POSIX-specified -.BR posix_madvise (3) -function, and the values have the same meanings, with the exception of -.BR MADV_DONTNEED . -.P -The advice is indicated in the -.I advice -argument, which is one of the following: -.TP -.B MADV_NORMAL -No special treatment. -This is the default. -.TP -.B MADV_RANDOM -Expect page references in random order. -(Hence, read ahead may be less useful than normally.) -.TP -.B 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.) -.TP -.B MADV_WILLNEED -Expect access in the near future. -(Hence, it might be a good idea to read some pages ahead.) -.TP -.B 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.) -.IP -After a successful -.B 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. -.IP -Note that, when applied to shared mappings, -.B 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. -.IP -.B MADV_DONTNEED -cannot be applied to locked pages, or -.B VM_PFNMAP -pages. -(Pages marked with the kernel-internal -.B VM_PFNMAP -.\" http://lwn.net/Articles/162860/ -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.) -.IP -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 length is rounded up -to a multiple of the underlying Huge TLB page size. -.\" -.\" ====================================================================== -.\" -.SS Linux-specific advice values -The following Linux-specific -.I advice -values have no counterparts in the POSIX-specified -.BR posix_madvise (3), -and may or may not have counterparts in the -.BR madvise () -interface available on other implementations. -Note that some of these operations change the semantics of memory accesses. -.TP -.BR MADV_REMOVE " (since Linux 2.6.16)" -.\" commit f6b3ec238d12c8cc6cc71490c6e3127988460349 -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 -.BR fallocate (2)). -Subsequent accesses in the specified address range will see -data with a value of zero. -.\" Databases want to use this feature to drop a section of their -.\" bufferpool (shared memory segments) - without writing back to -.\" disk/swap space. This feature is also useful for supporting -.\" hot-plug memory on UML. -.IP -The specified address range must be mapped shared and writable. -This flag cannot be applied to locked pages, or -.B VM_PFNMAP -pages. -.IP -In the initial implementation, only -.BR tmpfs (5) -supported -.BR MADV_REMOVE ; -but since Linux 3.5, -.\" commit 3f31d07571eeea18a7d34db9af21d2285b807a17 -any filesystem which supports the -.BR fallocate (2) -.B FALLOC_FL_PUNCH_HOLE -mode also supports -.BR MADV_REMOVE . -Filesystems which do not support -.B MADV_REMOVE -fail with the error -.BR EOPNOTSUPP . -.IP -Support for the Huge TLB filesystem was added in Linux v4.3. -.TP -.BR MADV_DONTFORK " (since Linux 2.6.16)" -.\" commit f822566165dd46ff5de9bf895cfa6c51f53bb0c4 -.\" See http://lwn.net/Articles/171941/ -Do not make the pages in this range available to the child after a -.BR fork (2). -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 -.BR fork (2). -(Such page relocations cause problems for hardware that -DMAs into the page.) -.\" [PATCH] madvise MADV_DONTFORK/MADV_DOFORK -.\" Currently, copy-on-write may change the physical address of -.\" a page even if the user requested that the page is pinned in -.\" memory (either by mlock or by get_user_pages). This happens -.\" if the process forks meanwhile, and the parent writes to that -.\" page. As a result, the page is orphaned: in case of -.\" get_user_pages, the application will never see any data hardware -.\" DMA's into this page after the COW. In case of mlock'd memory, -.\" the parent is not getting the realtime/security benefits of mlock. -.\" -.\" In particular, this affects the Infiniband modules which do DMA from -.\" and into user pages all the time. -.\" -.\" This patch adds madvise options to control whether memory range is -.\" inherited across fork. Useful e.g. for when hardware is doing DMA -.\" from/into these pages. Could also be useful to an application -.\" wanting to speed up its forks by cutting large areas out of -.\" consideration. -.\" -.\" SEE ALSO: http://lwn.net/Articles/171941/ -.\" "Tweaks to madvise() and posix_fadvise()", 14 Feb 2006 -.TP -.BR MADV_DOFORK " (since Linux 2.6.16)" -Undo the effect of -.BR MADV_DONTFORK , -restoring the default behavior, whereby a mapping is inherited across -.BR fork (2). -.TP -.BR MADV_HWPOISON " (since Linux 2.6.32)" -.\" commit 9893e49d64a4874ea67849ee2cfbf3f3d6817573 -Poison the pages in the range specified by -.I addr -and -.I length -and handle subsequent references to those pages -like a hardware memory corruption. -This operation is available only for privileged -.RB ( CAP_SYS_ADMIN ) -processes. -This operation may result in the calling process receiving a -.B SIGBUS -and the page being unmapped. -.IP -This feature is intended for testing of memory error-handling code; -it is available only if the kernel was configured with -.BR CONFIG_MEMORY_FAILURE . -.TP -.BR MADV_MERGEABLE " (since Linux 2.6.32)" -.\" commit f8af4da3b4c14e7267c4ffb952079af3912c51c5 -Enable Kernel Samepage Merging (KSM) for the pages in the range specified by -.I addr -and -.IR length . -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 -.BR mmap (2)). -.IP -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 -.I Documentation/admin\-guide/mm/ksm.rst -for more details. -.IP -The -.B MADV_MERGEABLE -and -.B MADV_UNMERGEABLE -operations are available only if the kernel was configured with -.BR CONFIG_KSM . -.TP -.BR MADV_UNMERGEABLE " (since Linux 2.6.32)" -Undo the effect of an earlier -.B MADV_MERGEABLE -operation on the specified address range; -KSM unmerges whatever pages it had merged in the address range specified by -.I addr -and -.IR length . -.TP -.BR MADV_SOFT_OFFLINE " (since Linux 2.6.33)" -.\" commit afcf938ee0aac4ef95b1a23bac704c6fbeb26de6 -Soft offline the pages in the range specified by -.I addr -and -.IR length . -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 -.B MADV_SOFT_OFFLINE -operation is invisible to (i.e., does not change the semantics of) -the calling process. -.IP -This feature is intended for testing of memory error-handling code; -it is available only if the kernel was configured with -.BR CONFIG_MEMORY_FAILURE . -.TP -.BR MADV_HUGEPAGE " (since Linux 2.6.38)" -.\" commit 0af4e98b6b095c74588af04872f83d333c958c32 -.\" http://lwn.net/Articles/358904/ -.\" https://lwn.net/Articles/423584/ -Enable Transparent Huge Pages (THP) for pages in the range specified by -.I addr -and -.IR length . -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 -.BR posix_memalign (2)). -.IP -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 -.I Documentation/admin\-guide/mm/transhuge.rst -for more details. -.IP -Most common kernels configurations provide -.BR MADV_HUGEPAGE -style -behavior by default, and thus -.B MADV_HUGEPAGE -is normally not necessary. -It is mostly intended for embedded systems, where -.BR 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 -.B 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. -.IP -.\" commit 99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0 -Since Linux 5.4, -automatic scan of eligible areas and replacement by huge pages works with -private anonymous pages (see -.BR mmap (2)), -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 -\[em]including tmpfs (see -.BR tmpfs (2))\[em] -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. -.IP -The VMA must not be marked -.BR VM_NOHUGEPAGE , -.BR VM_HUGETLB , -.BR VM_IO , -.BR VM_DONTEXPAND , -.BR VM_MIXEDMAP , -or -.BR 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 -.B PR_SET_THP_DISABLE -set (see -.BR prctl (2)). -.IP -The -.BR MADV_HUGEPAGE , -.BR MADV_NOHUGEPAGE , -and -.B MADV_COLLAPSE -operations are available only if the kernel was configured with -.B CONFIG_TRANSPARENT_HUGEPAGE -and file/shmem memory is only supported if the kernel was configured with -.BR CONFIG_READ_ONLY_THP_FOR_FS . -.TP -.BR MADV_NOHUGEPAGE " (since Linux 2.6.38)" -Ensures that memory in the address range specified by -.I addr -and -.I length -will not be backed by transparent hugepages. -.TP -.BR MADV_COLLAPSE " (since Linux 6.1)" -.\" commit 7d8faaf155454f8798ec56404faca29a82689c77 -.\" commit 34488399fa08faaf664743fa54b271eb6f9e1321 -Perform a best-effort synchronous collapse of -the native pages mapped by the memory range -into Transparent Huge Pages (THPs). -.B 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. -.IP -.B MADV_COLLAPSE -supports private anonymous pages (see -.BR mmap (2)), -shmem pages, -and file-backed pages. -See -.B 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. -.B MADV_COLLAPSE -will automatically clamp the provided range to be hugepage-aligned. -.IP -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. -.IP -.B MADV_COLLAPSE -is independent of any sysfs -(see -.BR sysfs (5)) -setting under -.IR /sys/kernel/mm/transparent_hugepage , -both in terms of determining THP eligibility, -and allocation semantics. -See Linux kernel source file -.I Documentation/admin\-guide/mm/transhuge.rst -for more information. -.B MADV_COLLAPSE -also ignores -.B 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 -.B VM_NOHUGEPAGE -is still respected). -.IP -When the system has multiple NUMA nodes, -the hugepage will be allocated from -the node providing the most native pages. -.IP -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\[en]failed code will be set in -.IR errno . -.TP -.BR MADV_DONTDUMP " (since Linux 3.4)" -.\" commit 909af768e88867016f427264ae39d27a57b6a8ed -.\" commit accb61fe7bb0f5c2a4102239e4981650f9048519 -Exclude from a core dump those pages in the range specified by -.I addr -and -.IR length . -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 -.B MADV_DONTDUMP -takes precedence over the bit mask that is set via the -.IR /proc/ pid /coredump_filter -file (see -.BR core (5)). -.TP -.BR MADV_DODUMP " (since Linux 3.4)" -Undo the effect of an earlier -.BR MADV_DONTDUMP . -.TP -.BR MADV_FREE " (since Linux 4.5)" -The application no longer requires the pages in the range specified by -.I addr -and -.IR len . -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 -.B 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. -.IP -The -.B MADV_FREE -operation -can be applied only to private anonymous pages (see -.BR mmap (2)). -Before Linux 4.12, -.\" commit 93e06c7a645343d222c9a838834a51042eebbbf7 -when freeing pages on a swapless system, -the pages in the given range are freed instantly, -regardless of memory pressure. -.TP -.BR MADV_WIPEONFORK " (since Linux 4.14)" -.\" commit d2cd9ede6e193dd7d88b6d27399e96229a551b19 -Present the child process with zero-filled memory in this range after a -.BR fork (2). -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. -.IP -The -.B MADV_WIPEONFORK -operation can be applied only to private anonymous pages (see -.BR mmap (2)). -.IP -Within the child created by -.BR fork (2), -the -.B MADV_WIPEONFORK -setting remains in place on the specified address range. -This setting is cleared during -.BR execve (2). -.TP -.BR MADV_KEEPONFORK " (since Linux 4.14)" -.\" commit d2cd9ede6e193dd7d88b6d27399e96229a551b19 -Undo the effect of an earlier -.BR MADV_WIPEONFORK . -.TP -.BR MADV_COLD " (since Linux 5.4)" -.\" commit 9c276cc65a58faf98be8e56962745ec99ab87636 -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. -.TP -.BR MADV_PAGEOUT " (since Linux 5.4)" -.\" commit 1a4e58cce84ee88129d5d49c064bd2852b481357 -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. -.TP -.BR 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. -.IP -In contrast to -.BR MAP_POPULATE , -.B 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. -.IP -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 -.B SIGBUS -signal is not generated; instead, an error is returned. -.IP -If -.B MADV_POPULATE_READ -succeeds, -all page tables have been populated (prefaulted) readable once. -If -.B MADV_POPULATE_READ -fails, -some page tables might have been populated. -.IP -.B MADV_POPULATE_READ -cannot be applied to mappings without read permissions -and special mappings, -for example, -mappings marked with kernel-internal flags such as -.B VM_PFNMAP -or -.BR VM_IO , -or secret memory regions created using -.BR memfd_secret(2) . -.IP -Note that with -.BR MADV_POPULATE_READ , -the process can be killed at any moment when the system runs out of memory. -.TP -.BR 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. -.IP -In contrast to -.BR 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). -.IP -Depending on the underlying mapping, -preallocate memory or read the underlying file; -files with holes will preallocate blocks. -If populating fails, -a -.B SIGBUS -signal is not generated; instead, an error is returned. -.IP -If -.B MADV_POPULATE_WRITE -succeeds, -all page tables have been populated (prefaulted) writable once. -If -.B MADV_POPULATE_WRITE -fails, -some page tables might have been populated. -.IP -.B MADV_POPULATE_WRITE -cannot be applied to mappings without write permissions -and special mappings, -for example, -mappings marked with kernel-internal flags such as -.B VM_PFNMAP -or -.BR VM_IO , -or secret memory regions created using -.BR memfd_secret(2) . -.IP -Note that with -.BR MADV_POPULATE_WRITE , -the process can be killed at any moment when the system runs out of memory. -.SH RETURN VALUE -On success, -.BR madvise () -returns zero. -On error, it returns \-1 and -.I errno -is set to indicate the error. -.SH ERRORS -.TP -.B EACCES -.I advice -is -.BR MADV_REMOVE , -but the specified address range is not a shared writable mapping. -.TP -.B EAGAIN -A kernel resource was temporarily unavailable. -.TP -.B EBADF -The map exists, but the area maps something that isn't a file. -.TP -.B EBUSY -(for -.BR MADV_COLLAPSE ) -Could not charge hugepage to cgroup: cgroup limit exceeded. -.TP -.B EFAULT -.I advice -is -.B MADV_POPULATE_READ -or -.BR MADV_POPULATE_WRITE , -and populating (prefaulting) page tables failed because a -.B 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 -.B MADV_HWPOISON -flag described elsewhere in this page). -.TP -.B EINVAL -.I addr -is not page-aligned or -.I length -is negative. -.\" .I length -.\" is zero, -.TP -.B EINVAL -.I advice -is not a valid. -.TP -.B EINVAL -.I advice -is -.B MADV_COLD -or -.B MADV_PAGEOUT -and the specified address range includes locked, Huge TLB pages, or -.B VM_PFNMAP -pages. -.TP -.B EINVAL -.I advice -is -.B MADV_DONTNEED -or -.B MADV_REMOVE -and the specified address range includes locked, Huge TLB pages, or -.B VM_PFNMAP -pages. -.TP -.B EINVAL -.I advice -is -.B MADV_MERGEABLE -or -.BR MADV_UNMERGEABLE , -but the kernel was not configured with -.BR CONFIG_KSM . -.TP -.B EINVAL -.I advice -is -.B MADV_FREE -or -.B MADV_WIPEONFORK -but the specified address range includes file, Huge TLB, -.BR MAP_SHARED , -or -.B VM_PFNMAP -ranges. -.TP -.B EINVAL -.I advice -is -.B MADV_POPULATE_READ -or -.BR 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 -.B VM_IO -or -.BR VM_PFNMAP , -or secret memory regions created using -.BR memfd_secret(2) . -.TP -.B EIO -(for -.BR MADV_WILLNEED ) -Paging in this area would exceed the process's -maximum resident set size. -.TP -.B ENOMEM -(for -.BR MADV_WILLNEED ) -Not enough memory: paging in failed. -.TP -.B ENOMEM -(for -.BR MADV_COLLAPSE ) -Not enough memory: could not allocate hugepage. -.TP -.B ENOMEM -Addresses in the specified range are not currently -mapped, or are outside the address space of the process. -.TP -.B ENOMEM -.I advice -is -.B MADV_POPULATE_READ -or -.BR MADV_POPULATE_WRITE , -and populating (prefaulting) page tables failed because there was not enough -memory. -.TP -.B EPERM -.I advice -is -.BR MADV_HWPOISON , -but the caller does not have the -.B CAP_SYS_ADMIN -capability. -.TP -.B EHWPOISON -.I advice -is -.B MADV_POPULATE_READ -or -.BR MADV_POPULATE_WRITE , -and populating (prefaulting) page tables failed because a HW poisoned page -(HW poisoned pages can, -for example, -be created using the -.B MADV_HWPOISON -flag described elsewhere in this page) -was encountered. -.SH VERSIONS -Versions of this system call, implementing a wide variety of -.I advice -values, exist on many other implementations. -Other implementations typically implement at least the flags listed -above under -.IR "Conventional advice flags" , -albeit with some variation in semantics. -.P -POSIX.1-2001 describes -.BR posix_madvise (3) -with constants -.BR POSIX_MADV_NORMAL , -.BR POSIX_MADV_RANDOM , -.BR POSIX_MADV_SEQUENTIAL , -.BR POSIX_MADV_WILLNEED , -and -.BR POSIX_MADV_DONTNEED , -and so on, with behavior close to the similarly named flags listed above. -.SS Linux -The Linux implementation requires that the address -.I addr -be page-aligned, and allows -.I length -to be zero. -If there are some parts of the specified address range -that are not mapped, the Linux version of -.BR madvise () -ignores them and applies the call to the rest (but returns -.B ENOMEM -from the system call, as it should). -.P -.I madvise(0,\ 0,\ advice) -will return zero iff -.I advice -is supported by the kernel and can be relied on to probe for support. -.SH STANDARDS -None. -.SH HISTORY -First appeared in 4.4BSD. -.P -Since Linux 3.18, -.\" commit d3ac21cacc24790eb45d735769f35753f5b56ceb -support for this system call is optional, -depending on the setting of the -.B CONFIG_ADVISE_SYSCALLS -configuration option. -.SH SEE ALSO -.BR getrlimit (2), -.BR memfd_secret (2), -.BR mincore (2), -.BR mmap (2), -.BR mprotect (2), -.BR msync (2), -.BR munmap (2), -.BR prctl (2), -.BR process_madvise (2), -.BR posix_madvise (3), -.BR core (5) |