'\" t
.\"     Title: kmalloc
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: January 2017
.\"    Manual: Memory Management in Linux
.\"    Source: Kernel Hackers Manual 4.8.15
.\"  Language: English
.\"
.TH "KMALLOC" "9" "January 2017" "Kernel Hackers Manual 4\&.8\&." "Memory Management in Linux"
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.SH "NAME"
kmalloc \- allocate memory
.SH "SYNOPSIS"
.HP \w'void\ *\ kmalloc('u
.BI "void * kmalloc(size_t\ " "size" ", gfp_t\ " "flags" ");"
.SH "ARGUMENTS"
.PP
\fIsize\fR
.RS 4
how many bytes of memory are required\&.
.RE
.PP
\fIflags\fR
.RS 4
the type of memory to allocate\&.
.RE
.SH "DESCRIPTION"
.PP
kmalloc is the normal method of allocating memory for objects smaller than page size in the kernel\&.
.PP
The
\fIflags\fR
argument may be one of:
.PP
\fBGFP_USER\fR
\- Allocate memory on behalf of user\&. May sleep\&.
.PP
\fBGFP_KERNEL\fR
\- Allocate normal kernel ram\&. May sleep\&.
.PP
\fBGFP_ATOMIC\fR
\- Allocation will not sleep\&. May use emergency pools\&. For example, use this inside interrupt handlers\&.
.PP
\fBGFP_HIGHUSER\fR
\- Allocate pages from high memory\&.
.PP
\fBGFP_NOIO\fR
\- Do not do any I/O at all while trying to get memory\&.
.PP
\fBGFP_NOFS\fR
\- Do not make any fs calls while trying to get memory\&.
.PP
\fBGFP_NOWAIT\fR
\- Allocation will not sleep\&.
.PP
\fB__GFP_THISNODE\fR
\- Allocate node\-local memory only\&.
.PP
\fBGFP_DMA\fR
\- Allocation suitable for DMA\&. Should only be used for
\fBkmalloc\fR
caches\&. Otherwise, use a slab created with SLAB_DMA\&.
.PP
Also it is possible to set different flags by OR\*(Aqing in one or more of the following additional
\fIflags\fR:
.PP
\fB__GFP_COLD\fR
\- Request cache\-cold pages instead of trying to return cache\-warm pages\&.
.PP
\fB__GFP_HIGH\fR
\- This allocation has high priority and may use emergency pools\&.
.PP
\fB__GFP_NOFAIL\fR
\- Indicate that this allocation is in no way allowed to fail (think twice before using)\&.
.PP
\fB__GFP_NORETRY\fR
\- If memory is not immediately available, then give up at once\&.
.PP
\fB__GFP_NOWARN\fR
\- If allocation fails, don\*(Aqt issue any warnings\&.
.PP
\fB__GFP_REPEAT\fR
\- If allocation fails initially, try once more before failing\&.
.PP
There are other flags available as well, but these are not intended for general use, and so are not documented here\&. For a full list of potential flags, always refer to linux/gfp\&.h\&.
.SH "COPYRIGHT"
.br