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NetBSD 6.1.5 - man page for vmem_xalloc (netbsd section 9)

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VMEM(9) 			  BSD Kernel Developer's Manual 			  VMEM(9)

NAME
     vmem -- virtual memory allocator

SYNOPSIS
     #include <sys/vmem.h>

     vmem_t *
     vmem_create(const char *name, vmem_addr_t base, vmem_size_t size, vmem_size_t quantum,
	 int (*allocfn)(void *, vmem_size_t, vmem_size_t *, vm_flag_t, vmem_addr_t *),
	 void (*freefn)(void *, vmem_addr_t, vmem_size_t), void *arg, vmem_size_t qcache_max,
	 vm_flag_t flags, int ipl);

     int
     vmem_add(vmem_t *vm, vmem_addr_t addr, vmem_size_t size, vm_flag_t flags,
	 vmem_addr_t *addrp);

     int
     vmem_xalloc(vmem_t *vm, vmem_size_t size, vmem_size_t align, vmem_size_t phase,
	 vmem_size_t nocross, vmem_addr_t minaddr, vmem_addr_t maxaddr, vm_flag_t flags,
	 vmem_addr_t *addrp);

     void
     vmem_xfree(vmem_t *vm, vmem_addr_t addr, vmem_size_t size);

     int
     vmem_alloc(vmem_t *vm, vmem_size_t size, vm_flag_t flags, vmem_addr_t *addrp);

     void
     vmem_free(vmem_t *vm, vmem_addr_t addr, vmem_size_t size);

     void
     vmem_destroy(vmem_t *vm);

DESCRIPTION
     The vmem is a general purpose resource allocator.	Despite its name, it can be used for
     arbitrary resources other than virtual memory.

     vmem_create() creates a new vmem arena.

     name	 The string to describe the vmem.

     base	 The start address of the initial span.  Pass 0 if no initial span is required.

     size	 The size of the initial span.	Pass 0 if no initial span is required.

     quantum	 The smallest unit of allocation.

     allocfn	 The callback function used to import spans from the backend arena.  Set both
		 allocfn and freefn to NULL to disable automatic imports.  vmem calls
		 (*allocfn)(arg, size, &actualsize, flags, &addrp) to import a span of size at
		 least size.  allocfn should accept the same flags as vmem_alloc().  allocfn must
		 return ENOMEM to indicate failure, or 0 on success.  If allocfn succeeds, it
		 must write the actual size of the allocation to actualsize and the starting
		 address of the imported span to addrp.  The actual size will always be greater
		 than or equal to the requested size.

     freefn	 The callback function used to free spans to the backend arena.  freefn may be
		 NULL even if allocfn is not NULL.  vmem calls (*freefn)(arg, addr, size) to
		 return to arg a span of size size, starting at addr, that was previously allo-
		 cated by allocfn.

     arg	 The backend arena.  arg may be NULL.  vmem passes arg as the first argument of
		 allocfn and freefn.

     qcache_max  The largest size of allocations which can be served by quantum cache.	It is
		 merely a hint and can be ignored.

     flags	 Either of:

		 VM_SLEEP    Can sleep until enough resources are available.

		 VM_NOSLEEP  Don't sleep.  Immediately return NULL if there are not enough
			     resources available.

     ipl	 Interrupt level to be blocked for allocating from vmem.

     vmem_add() adds a span of size size starting at addr to the arena.  Returns 0 on success,
     ENOMEM on failure.  flags should be one of:

     VM_SLEEP	 Can sleep until enough resources are available.

     VM_NOSLEEP  Don't sleep.  Immediately return ENOMEM if there are not enough resources avail-
		 able.

     vmem_xalloc() allocates a resource from the arena.

     vm       The arena which we allocate from.

     size     Specify the size of the allocation.

     align    If zero, don't care about the alignment of the allocation.  Otherwise, request a
	      resource segment starting at offset phase from an align aligned boundary.

     phase    See the above description of align.  If align is zero, phase should be zero.  Oth-
	      erwise, phase should be smaller than align.

     nocross  Request a resource which doesn't cross nocross aligned boundary.

     minaddr  Specify the minimum address which can be allocated, or VMEM_ADDR_MIN if the caller
	      does not care.

     maxaddr  Specify the maximum address which can be allocated, or VMEM_ADDR_MAX if the caller
	      does not care.

     flags    A bitwise OR of an allocation strategy and a sleep flag.

	      The allocation strategy is one of:

	      VM_BESTFIT     Prefer space efficiency.

	      VM_INSTANTFIT  Prefer performance.

	      The sleep flag should be one of:

	      VM_SLEEP	  Can sleep until enough resources are available.

	      VM_NOSLEEP  Don't sleep.	Immediately return ENOMEM if there are not enough
			  resources available.

     addrp    On success, if addrp is not NULL, vmem_xalloc() overwrites it with the start
	      address of the allocated span.

     vmem_xfree() frees resource allocated by vmem_xalloc() to the arena.

     vm    The arena which we free to.

     addr  The resource being freed.  It must be the one returned by vmem_xalloc().  Notably, it
	   must not be the one from vmem_alloc().  Otherwise, the behaviour is undefined.

     size  The size of the resource being freed.  It must be the same as the size argument used
	   for vmem_xalloc().

     vmem_alloc() allocates a resource from the arena.

     vm     The arena which we allocate from.

     size   Specify the size of the allocation.

     flags  A bitwise OR of an allocation strategy and a sleep flag.

	    The allocation strategy is one of:

	    VM_BESTFIT	   Prefer space efficiency.

	    VM_INSTANTFIT  Prefer performance.

	    The sleep flag should be one of:

	    VM_SLEEP	Can sleep until enough resources are available.

	    VM_NOSLEEP	Don't sleep.  Immediately return ENOMEM if there are not enough resources
			available.

     addrp  On success, if addrp is not NULL, vmem_alloc() overwrites it with the start address
	    of the allocated span.

     vmem_free() frees resource allocated by vmem_alloc() to the arena.

     vm    The arena which we free to.

     addr  The resource being freed.  It must be the one returned by vmem_alloc().  Notably, it
	   must not be the one from vmem_xalloc().  Otherwise, the behaviour is undefined.

     size  The size of the resource being freed.  It must be the same as the size argument used
	   for vmem_alloc().

     vmem_destroy() destroys a vmem arena.

     vm  The vmem arena being destroyed.  The caller should ensure that no one will use it any-
	 more.

RETURN VALUES
     vmem_create() return a pointer to the newly allocated vmem_t.  Otherwise, it returns NULL.

     On success, vmem_xalloc() and vmem_alloc() return 0.  Otherwise, ENOMEM is returned.

CODE REFERENCES
     The vmem subsystem is implemented within the file sys/kern/subr_vmem.c.

SEE ALSO
     intro(9), kmem(9), memoryallocators(9), uvm(9)

     Jeff Bonwick and Jonathan Adams, "Magazines and Vmem: Extending the Slab Allocator to Many
     CPUs and Arbitrary Resources", 2001 USENIX Annual Technical Conference, 2001.

AUTHORS
     This implementation of vmem was written by YAMAMOTO Takashi.

BUGS
     vmem relies on malloc(9), pool(9), and RUN_ONCE(9), so it cannot be used as early during
     system bootstrap as extent(9).

BSD					September 2, 2011				      BSD
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