freebsd-skq/share/man/man9/contigmalloc.9
Mark Johnston 9978bd996b Add malloc_domainset(9) and _domainset variants to other allocator KPIs.
Remove malloc_domain(9) and most other _domain KPIs added in r327900.
The new functions allow the caller to specify a general NUMA domain
selection policy, rather than specifically requesting an allocation from
a specific domain.  The latter policy tends to interact poorly with
M_WAITOK, resulting in situations where a caller is blocked indefinitely
because the specified domain is depleted.  Most existing consumers of
the _domain KPIs are converted to instead use a DOMAINSET_PREF() policy,
in which we fall back to other domains to satisfy the allocation
request.

This change also defines a set of DOMAINSET_FIXED() policies, which
only permit allocations from the specified domain.

Discussed with:	gallatin, jeff
Reported and tested by:	pho (previous version)
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D17418
2018-10-30 18:26:34 +00:00

164 lines
4.2 KiB
Groff

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.Dd October 30, 2018
.Dt CONTIGMALLOC 9
.Os
.Sh NAME
.Nm contigmalloc , contigfree
.Nd manage contiguous kernel physical memory
.Sh SYNOPSIS
.In sys/types.h
.In sys/malloc.h
.Ft "void *"
.Fo contigmalloc
.Fa "unsigned long size"
.Fa "struct malloc_type *type"
.Fa "int flags"
.Fa "vm_paddr_t low"
.Fa "vm_paddr_t high"
.Fa "unsigned long alignment"
.Fa "vm_paddr_t boundary"
.Fc
.Ft void
.Fo contigfree
.Fa "void *addr"
.Fa "unsigned long size"
.Fa "struct malloc_type *type"
.Fc
.In sys/param.h
.In sys/domainset.h
.Ft "void *"
.Fo contigmalloc_domainset
.Fa "unsigned long size"
.Fa "struct malloc_type *type"
.Fa "struct domainset *ds"
.Fa "int flags"
.Fa "vm_paddr_t low"
.Fa "vm_paddr_t high"
.Fa "unsigned long alignment"
.Fa "vm_paddr_t boundary"
.Fc
.Sh DESCRIPTION
The
.Fn contigmalloc
function allocates
.Fa size
bytes of contiguous physical memory that is aligned to
.Fa alignment
bytes, and which does not cross a boundary of
.Fa boundary
bytes.
If successful, the allocation will reside between physical addresses
.Fa low
and
.Fa high .
The returned pointer points to a wired kernel virtual
address range of
.Fa size
bytes allocated from the kernel virtual address (KVA) map.
.Pp
The
.Fn contigmalloc_domainset
variant allows the caller to additionally specify a
.Xr numa 4
domain selection policy.
See
.Xr domainset 9
for some example policies.
.Pp
The
.Fa flags
parameter modifies
.Fn contigmalloc Ns 's
behaviour as follows:
.Bl -tag -width indent
.It Dv M_ZERO
Causes the allocated physical memory to be zero filled.
.It Dv M_NOWAIT
Causes
.Fn contigmalloc
to return
.Dv NULL
if the request cannot be immediately fulfilled due to resource shortage.
.El
.Pp
Other flags (if present) are ignored.
.Pp
The
.Fn contigfree
function deallocates memory allocated by a previous call to
.Fn contigmalloc
or
.Fn contigmalloc_domainset .
.Sh IMPLEMENTATION NOTES
The
.Fn contigmalloc
function does not sleep waiting for memory resources to be freed up,
but instead actively reclaims pages before giving up.
However, unless
.Dv M_NOWAIT
is specified, it may select a page for reclamation that must first be
written to backing storage, causing it to sleep.
.Pp
The
.Fn contigfree
function does not accept
.Dv NULL
as an address input, unlike
.Xr free 9 .
.Sh RETURN VALUES
The
.Fn contigmalloc
function returns a kernel virtual address if allocation succeeds,
or
.Dv NULL
otherwise.
.Sh EXAMPLES
.Bd -literal
void *p;
p = contigmalloc(8192, M_DEVBUF, M_ZERO, 0, (1L << 22),
32 * 1024, 1024 * 1024);
.Ed
.Pp
Ask for 8192 bytes of zero-filled memory residing between physical
address 0 and 4194303 inclusive, aligned to a 32K boundary and not
crossing a 1M address boundary.
.Sh DIAGNOSTICS
The
.Fn contigmalloc
function will panic if
.Fa size
is zero, or if
.Fa alignment
or
.Fa boundary
is not a power of two.
.Sh SEE ALSO
.Xr malloc 9 ,
.Xr memguard 9