1.\"-
2.\" Copyright (c) 2001 Dag-Erling Co�dan Sm�rgrav
3.\" All rights reserved.
4.\"
5.\" Redistribution and use in source and binary forms, with or without
6.\" modification, are permitted provided that the following conditions
7.\" are met:
8.\" 1. Redistributions of source code must retain the above copyright
9.\" notice, this list of conditions and the following disclaimer.
10.\" 2. Redistributions in binary form must reproduce the above copyright
11.\" notice, this list of conditions and the following disclaimer in the
12.\" documentation and/or other materials provided with the distribution.
13.\"
14.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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| 1.\"-
2.\" Copyright (c) 2001 Dag-Erling Co�dan Sm�rgrav
3.\" All rights reserved.
4.\"
5.\" Redistribution and use in source and binary forms, with or without
6.\" modification, are permitted provided that the following conditions
7.\" are met:
8.\" 1. Redistributions of source code must retain the above copyright
9.\" notice, this list of conditions and the following disclaimer.
10.\" 2. Redistributions in binary form must reproduce the above copyright
11.\" notice, this list of conditions and the following disclaimer in the
12.\" documentation and/or other materials provided with the distribution.
13.\"
14.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24.\" SUCH DAMAGE.
25.\"
|
26.\" $FreeBSD: head/share/man/man9/zone.9 179880 2008-06-19 18:33:38Z remko $
| 26.\" $FreeBSD: head/share/man/man9/zone.9 213910 2010-10-16 04:14:45Z lstewart $
|
27.\"
| 27.\"
|
28.Dd June 19, 2008
| 28.Dd October 9, 2010
|
29.Dt ZONE 9
30.Os
31.Sh NAME
32.Nm uma_zcreate ,
33.Nm uma_zalloc ,
34.Nm uma_zalloc_arg ,
35.Nm uma_zfree ,
36.Nm uma_zfree_arg ,
37.Nm uma_zdestroy ,
| 29.Dt ZONE 9
30.Os
31.Sh NAME
32.Nm uma_zcreate ,
33.Nm uma_zalloc ,
34.Nm uma_zalloc_arg ,
35.Nm uma_zfree ,
36.Nm uma_zfree_arg ,
37.Nm uma_zdestroy ,
|
38.Nm uma_zone_set_max
| 38.Nm uma_zone_set_max,
39.Nm uma_zone_get_max,
40.Nm uma_zone_get_cur
|
39.Nd zone allocator
40.Sh SYNOPSIS
41.In sys/param.h
42.In sys/queue.h
43.In vm/uma.h
44.Ft uma_zone_t
45.Fo uma_zcreate
46.Fa "char *name" "int size"
47.Fa "uma_ctor ctor" "uma_dtor dtor" "uma_init uminit" "uma_fini fini"
48.Fa "int align" "u_int16_t flags"
49.Fc
50.Ft "void *"
51.Fn uma_zalloc "uma_zone_t zone" "int flags"
52.Ft "void *"
53.Fn uma_zalloc_arg "uma_zone_t zone" "void *arg" "int flags"
54.Ft void
55.Fn uma_zfree "uma_zone_t zone" "void *item"
56.Ft void
57.Fn uma_zfree_arg "uma_zone_t zone" "void *item" "void *arg"
58.Ft void
59.Fn uma_zdestroy "uma_zone_t zone"
60.Ft void
61.Fn uma_zone_set_max "uma_zone_t zone" "int nitems"
| 41.Nd zone allocator
42.Sh SYNOPSIS
43.In sys/param.h
44.In sys/queue.h
45.In vm/uma.h
46.Ft uma_zone_t
47.Fo uma_zcreate
48.Fa "char *name" "int size"
49.Fa "uma_ctor ctor" "uma_dtor dtor" "uma_init uminit" "uma_fini fini"
50.Fa "int align" "u_int16_t flags"
51.Fc
52.Ft "void *"
53.Fn uma_zalloc "uma_zone_t zone" "int flags"
54.Ft "void *"
55.Fn uma_zalloc_arg "uma_zone_t zone" "void *arg" "int flags"
56.Ft void
57.Fn uma_zfree "uma_zone_t zone" "void *item"
58.Ft void
59.Fn uma_zfree_arg "uma_zone_t zone" "void *item" "void *arg"
60.Ft void
61.Fn uma_zdestroy "uma_zone_t zone"
62.Ft void
63.Fn uma_zone_set_max "uma_zone_t zone" "int nitems"
|
| 64.Ft int
65.Fn uma_zone_get_max "uma_zone_t zone"
66.Ft int
67.Fn uma_zone_get_cur "uma_zone_t zone"
|
62.Sh DESCRIPTION
63The zone allocator provides an efficient interface for managing
64dynamically-sized collections of items of similar size.
65The zone allocator can work with preallocated zones as well as with
66runtime-allocated ones, and is therefore available much earlier in the
67boot process than other memory management routines.
68.Pp
69A zone is an extensible collection of items of identical size.
70The zone allocator keeps track of which items are in use and which
71are not, and provides functions for allocating items from the zone and
72for releasing them back (which makes them available for later use).
73.Pp
74After the first allocation of an item,
75it will have been cleared to zeroes, however subsequent allocations
76will retain the contents as of the last free.
77.Pp
78The
79.Fn uma_zcreate
80function creates a new zone from which items may then be allocated from.
81The
82.Fa name
83argument is a text name of the zone for debugging and stats; this memory
84should not be freed until the zone has been deallocated.
85.Pp
86The
87.Fa ctor
88and
89.Fa dtor
90arguments are callback functions that are called by
91the uma subsystem at the time of the call to
92.Fn uma_zalloc
93and
94.Fn uma_zfree
95respectively.
96Their purpose is to provide hooks for initializing or
97destroying things that need to be done at the time of the allocation
98or release of a resource.
99A good usage for the
100.Fa ctor
101and
102.Fa dtor
103callbacks
104might be to adjust a global count of the number of objects allocated.
105.Pp
106The
107.Fa uminit
108and
109.Fa fini
110arguments are used to optimize the allocation of
111objects from the zone.
112They are called by the uma subsystem whenever
113it needs to allocate or free several items to satisfy requests or memory
114pressure.
115A good use for the
116.Fa uminit
117and
118.Fa fini
119callbacks might be to
120initialize and destroy mutexes contained within the object.
121This would
122allow one to re-use already initialized mutexes when an object is returned
123from the uma subsystem's object cache.
124They are not called on each call to
125.Fn uma_zalloc
126and
127.Fn uma_zfree
128but rather in a batch mode on several objects.
129.Pp
130To allocate an item from a zone, simply call
131.Fn uma_zalloc
132with a pointer to that zone
133and set the
134.Fa flags
135argument to selected flags as documented in
136.Xr malloc 9 .
137It will return a pointer to an item if successful,
138or
139.Dv NULL
140in the rare case where all items in the zone are in use and the
141allocator is unable to grow the zone
142or when
143.Dv M_NOWAIT
144is specified.
145.Pp
146Items are released back to the zone from which they were allocated by
147calling
148.Fn uma_zfree
149with a pointer to the zone and a pointer to the item.
150.Pp
151The variations
152.Fn uma_zalloc_arg
153and
154.Fn uma_zfree_arg
155allow to
156specify an argument for the
157.Dv ctor
158and
159.Dv dtor
160functions, respectively.
161.Pp
162Created zones,
163which are empty,
164can be destroyed using
165.Fn uma_zdestroy ,
166freeing all memory that was allocated for the zone.
167All items allocated from the zone with
168.Fn uma_zalloc
169must have been freed with
170.Fn uma_zfree
171before.
172.Pp
| 68.Sh DESCRIPTION
69The zone allocator provides an efficient interface for managing
70dynamically-sized collections of items of similar size.
71The zone allocator can work with preallocated zones as well as with
72runtime-allocated ones, and is therefore available much earlier in the
73boot process than other memory management routines.
74.Pp
75A zone is an extensible collection of items of identical size.
76The zone allocator keeps track of which items are in use and which
77are not, and provides functions for allocating items from the zone and
78for releasing them back (which makes them available for later use).
79.Pp
80After the first allocation of an item,
81it will have been cleared to zeroes, however subsequent allocations
82will retain the contents as of the last free.
83.Pp
84The
85.Fn uma_zcreate
86function creates a new zone from which items may then be allocated from.
87The
88.Fa name
89argument is a text name of the zone for debugging and stats; this memory
90should not be freed until the zone has been deallocated.
91.Pp
92The
93.Fa ctor
94and
95.Fa dtor
96arguments are callback functions that are called by
97the uma subsystem at the time of the call to
98.Fn uma_zalloc
99and
100.Fn uma_zfree
101respectively.
102Their purpose is to provide hooks for initializing or
103destroying things that need to be done at the time of the allocation
104or release of a resource.
105A good usage for the
106.Fa ctor
107and
108.Fa dtor
109callbacks
110might be to adjust a global count of the number of objects allocated.
111.Pp
112The
113.Fa uminit
114and
115.Fa fini
116arguments are used to optimize the allocation of
117objects from the zone.
118They are called by the uma subsystem whenever
119it needs to allocate or free several items to satisfy requests or memory
120pressure.
121A good use for the
122.Fa uminit
123and
124.Fa fini
125callbacks might be to
126initialize and destroy mutexes contained within the object.
127This would
128allow one to re-use already initialized mutexes when an object is returned
129from the uma subsystem's object cache.
130They are not called on each call to
131.Fn uma_zalloc
132and
133.Fn uma_zfree
134but rather in a batch mode on several objects.
135.Pp
136To allocate an item from a zone, simply call
137.Fn uma_zalloc
138with a pointer to that zone
139and set the
140.Fa flags
141argument to selected flags as documented in
142.Xr malloc 9 .
143It will return a pointer to an item if successful,
144or
145.Dv NULL
146in the rare case where all items in the zone are in use and the
147allocator is unable to grow the zone
148or when
149.Dv M_NOWAIT
150is specified.
151.Pp
152Items are released back to the zone from which they were allocated by
153calling
154.Fn uma_zfree
155with a pointer to the zone and a pointer to the item.
156.Pp
157The variations
158.Fn uma_zalloc_arg
159and
160.Fn uma_zfree_arg
161allow to
162specify an argument for the
163.Dv ctor
164and
165.Dv dtor
166functions, respectively.
167.Pp
168Created zones,
169which are empty,
170can be destroyed using
171.Fn uma_zdestroy ,
172freeing all memory that was allocated for the zone.
173All items allocated from the zone with
174.Fn uma_zalloc
175must have been freed with
176.Fn uma_zfree
177before.
178.Pp
|
173The purpose of
| 179The
|
174.Fn uma_zone_set_max
| 180.Fn uma_zone_set_max
|
175is to limit the maximum amount of memory that the system can dedicated
176toward the zone specified by the
177.Fa zone
178argument.
| 181function limits the number of items
182.Pq and therefore memory
183that can be allocated to
184.Fa zone .
|
179The
180.Fa nitems
| 185The
186.Fa nitems
|
181argument gives the upper limit of items in the zone.
182This limits the total number of items in the zone which includes:
| 187argument specifies the requested upper limit number of items.
188The effective limit may end up being higher than requested, as the
189implementation will round up to ensure all memory pages allocated to the zone
190are utilised to capacity.
191The limit applies to the total number of items in the zone, which includes
|
183allocated items, free items and free items in the per-cpu caches.
184On systems with more than one CPU it may not be possible to allocate
185the specified number of items even when there is no shortage of memory,
186because all of the remaining free items may be in the caches of the
187other CPUs when the limit is hit.
| 192allocated items, free items and free items in the per-cpu caches.
193On systems with more than one CPU it may not be possible to allocate
194the specified number of items even when there is no shortage of memory,
195because all of the remaining free items may be in the caches of the
196other CPUs when the limit is hit.
|
| 197.Pp
198The
199.Fn uma_zone_get_max
200function returns the effective upper limit number of items for a zone.
201.Pp
202The
203.Fn uma_zone_get_cur
204function returns the approximate current occupancy of the zone.
205The returned value is approximate because appropriate synchronisation to
206determine an exact value is not performend by the implementation.
207This ensures low overhead at the expense of potentially stale data being used
208in the calculation.
|
188.Sh RETURN VALUES
189The
190.Fn uma_zalloc
191function returns a pointer to an item, or
192.Dv NULL
193if the zone ran out of unused items and the allocator was unable to
194enlarge it.
195.Sh SEE ALSO
196.Xr malloc 9
197.Sh HISTORY
198The zone allocator first appeared in
199.Fx 3.0 .
200It was radically changed in
201.Fx 5.0
202to function as a slab allocator.
203.Sh AUTHORS
204.An -nosplit
205The zone allocator was written by
206.An John S. Dyson .
207The zone allocator was rewritten in large parts by
208.An Jeff Roberson Aq jeff@FreeBSD.org
209to function as a slab allocator.
210.Pp
211This manual page was written by
212.An Dag-Erling Sm\(/orgrav Aq des@FreeBSD.org .
213Changes for UMA by
214.An Jeroen Ruigrok van der Werven Aq asmodai@FreeBSD.org .
| 209.Sh RETURN VALUES
210The
211.Fn uma_zalloc
212function returns a pointer to an item, or
213.Dv NULL
214if the zone ran out of unused items and the allocator was unable to
215enlarge it.
216.Sh SEE ALSO
217.Xr malloc 9
218.Sh HISTORY
219The zone allocator first appeared in
220.Fx 3.0 .
221It was radically changed in
222.Fx 5.0
223to function as a slab allocator.
224.Sh AUTHORS
225.An -nosplit
226The zone allocator was written by
227.An John S. Dyson .
228The zone allocator was rewritten in large parts by
229.An Jeff Roberson Aq jeff@FreeBSD.org
230to function as a slab allocator.
231.Pp
232This manual page was written by
233.An Dag-Erling Sm\(/orgrav Aq des@FreeBSD.org .
234Changes for UMA by
235.An Jeroen Ruigrok van der Werven Aq asmodai@FreeBSD.org .
|