diff options
Diffstat (limited to '')
| -rw-r--r-- | man2/move_pages.2 | 253 |
1 files changed, 253 insertions, 0 deletions
diff --git a/man2/move_pages.2 b/man2/move_pages.2 new file mode 100644 index 0000000..c2be4bb --- /dev/null +++ b/man2/move_pages.2 @@ -0,0 +1,253 @@ +.\" SPDX-License-Identifier: Linux-man-pages-copyleft-2-para +.\" +.\" This manpage is Copyright (C) 2006 Silicon Graphics, Inc. +.\" Christoph Lameter +.\" +.\" FIXME Should programs normally be using move_pages() directly, or should +.\" they rather be using interfaces in the numactl package? +.\" (e.g., compare with recommendation in mbind(2)). +.\" Does this page need to give advice on this topic? +.\" +.TH move_pages 2 2023-07-15 "Linux man-pages 6.05.01" +.SH NAME +move_pages \- move individual pages of a process to another node +.SH LIBRARY +NUMA (Non-Uniform Memory Access) policy library +.RI ( libnuma ", " \-lnuma ) +.SH SYNOPSIS +.nf +.B #include <numaif.h> +.PP +.BI "long move_pages(int " pid ", unsigned long " count ", \ +void *" pages [. count ], +.BI " const int " nodes [. count "], int " status [. count "], \ +int " flags ); +.fi +.SH DESCRIPTION +.BR move_pages () +moves the specified +.I pages +of the process +.I pid +to the memory nodes specified by +.IR nodes . +The result of the move is reflected in +.IR status . +The +.I flags +indicate constraints on the pages to be moved. +.PP +.I pid +is the ID of the process in which pages are to be moved. +If +.I pid +is 0, then +.BR move_pages () +moves pages of the calling process. +.PP +To move pages in another process requires the following privileges: +.IP \[bu] 3 +Up to and including Linux 4.12: +the caller must be privileged +.RB ( CAP_SYS_NICE ) +or the real or effective user ID of the calling process must match the +real or saved-set user ID of the target process. +.IP \[bu] +The older rules allowed the caller to discover various +virtual address choices made by the kernel that could lead +to the defeat of address-space-layout randomization +for a process owned by the same UID as the caller, +the rules were changed starting with Linux 4.13. +Since Linux 4.13, +.\" commit 197e7e521384a23b9e585178f3f11c9fa08274b9 +permission is governed by a ptrace access mode +.B PTRACE_MODE_READ_REALCREDS +check with respect to the target process; see +.BR ptrace (2). +.PP +.I count +is the number of pages to move. +It defines the size of the three arrays +.IR pages , +.IR nodes , +and +.IR status . +.PP +.I pages +is an array of pointers to the pages that should be moved. +These are pointers that should be aligned to page boundaries. +.\" FIXME Describe the result if pointers in the 'pages' array are +.\" not aligned to page boundaries +Addresses are specified as seen by the process specified by +.IR pid . +.PP +.I nodes +is an array of integers that specify the desired location for each page. +Each element in the array is a node number. +.I nodes +can also be NULL, in which case +.BR move_pages () +does not move any pages but instead will return the node +where each page currently resides, in the +.I status +array. +Obtaining the status of each page may be necessary to determine +pages that need to be moved. +.PP +.I status +is an array of integers that return the status of each page. +The array contains valid values only if +.BR move_pages () +did not return an error. +Preinitialization of the array to a value +which cannot represent a real numa node or valid error of status array +could help to identify pages that have been migrated. +.PP +.I flags +specify what types of pages to move. +.B MPOL_MF_MOVE +means that only pages that are in exclusive use by the process +are to be moved. +.B MPOL_MF_MOVE_ALL +means that pages shared between multiple processes can also be moved. +The process must be privileged +.RB ( CAP_SYS_NICE ) +to use +.BR MPOL_MF_MOVE_ALL . +.SS Page states in the status array +The following values can be returned in each element of the +.I status +array. +.TP +.B 0..MAX_NUMNODES +Identifies the node on which the page resides. +.TP +.B \-EACCES +The page is mapped by multiple processes and can be moved only if +.B MPOL_MF_MOVE_ALL +is specified. +.TP +.B \-EBUSY +The page is currently busy and cannot be moved. +Try again later. +This occurs if a page is undergoing I/O or another kernel subsystem +is holding a reference to the page. +.TP +.B \-EFAULT +This is a zero page or the memory area is not mapped by the process. +.TP +.B \-EIO +Unable to write back a page. +The page has to be written back +in order to move it since the page is dirty and the filesystem +does not provide a migration function that would allow the move +of dirty pages. +.TP +.B \-EINVAL +A dirty page cannot be moved. +The filesystem does not +provide a migration function and has no ability to write back pages. +.TP +.B \-ENOENT +The page is not present. +.TP +.B \-ENOMEM +Unable to allocate memory on target node. +.SH RETURN VALUE +On success +.BR move_pages () +returns zero. +.\" FIXME . Is the following quite true: does the wrapper in numactl +.\" do the right thing? +On error, it returns \-1, and sets +.I errno +to indicate the error. +If positive value is returned, it is the number of +nonmigrated pages. +.SH ERRORS +.TP +.B Positive value +The number of nonmigrated pages if they were the result of nonfatal +reasons (since +.\" commit a49bd4d7163707de377aee062f17befef6da891b +Linux 4.17). +.TP +.B E2BIG +Too many pages to move. +Since Linux 2.6.29, +.\" commit 3140a2273009c01c27d316f35ab76a37e105fdd8 +the kernel no longer generates this error. +.TP +.B EACCES +.\" FIXME Clarify "current cpuset" in the description of the EACCES error. +.\" Is that the cpuset of the caller or the target? +One of the target nodes is not allowed by the current cpuset. +.TP +.B EFAULT +Parameter array could not be accessed. +.TP +.B EINVAL +Flags other than +.B MPOL_MF_MOVE +and +.B MPOL_MF_MOVE_ALL +was specified or an attempt was made to migrate pages of a kernel thread. +.TP +.B ENODEV +One of the target nodes is not online. +.TP +.B EPERM +The caller specified +.B MPOL_MF_MOVE_ALL +without sufficient privileges +.RB ( CAP_SYS_NICE ). +Or, the caller attempted to move pages of a process belonging +to another user but did not have privilege to do so +.RB ( CAP_SYS_NICE ). +.TP +.B ESRCH +Process does not exist. +.SH STANDARDS +Linux. +.SH HISTORY +Linux 2.6.18. +.SH NOTES +For information on library support, see +.BR numa (7). +.PP +Use +.BR get_mempolicy (2) +with the +.B MPOL_F_MEMS_ALLOWED +flag to obtain the set of nodes that are allowed by +.\" FIXME Clarify "current cpuset". Is that the cpuset of the caller +.\" or the target? +the current cpuset. +Note that this information is subject to change at any +time by manual or automatic reconfiguration of the cpuset. +.PP +Use of this function may result in pages whose location +(node) violates the memory policy established for the +specified addresses (See +.BR mbind (2)) +and/or the specified process (See +.BR set_mempolicy (2)). +That is, memory policy does not constrain the destination +nodes used by +.BR move_pages (). +.PP +The +.I <numaif.h> +header is not included with glibc, but requires installing +.I libnuma\-devel +or a similar package. +.SH SEE ALSO +.BR get_mempolicy (2), +.BR mbind (2), +.BR set_mempolicy (2), +.BR numa (3), +.BR numa_maps (5), +.BR cpuset (7), +.BR numa (7), +.BR migratepages (8), +.BR numastat (8) |