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28 .\" @(#)mlock.2 8.2 (Berkeley) 12/11/93
37 .Nd lock (unlock) physical pages in memory
43 .Fn mlock "const void *addr" "size_t len"
45 .Fn munlock "const void *addr" "size_t len"
50 locks into memory the physical pages associated with the virtual address
58 system call unlocks pages previously locked by one or more
63 argument should be aligned to a multiple of the page size.
66 argument is not a multiple of the page size, it will be rounded up
68 The entire range must be allocated.
72 system call, the indicated pages will cause neither a non-resident page
73 nor address-translation fault until they are unlocked.
74 They may still cause protection-violation faults or TLB-miss faults on
75 architectures with software-managed TLBs.
76 The physical pages remain in memory until all locked mappings for the pages
78 Multiple processes may have the same physical pages locked via their own
79 virtual address mappings.
80 A single process may likewise have pages multiply-locked via different virtual
81 mappings of the same physical pages.
82 Unlocking is performed explicitly by
84 or implicitly by a call to
86 which deallocates the unmapped address range.
87 Locked mappings are not inherited by the child process after a
90 Since physical memory is a potentially scarce resource, processes are
91 limited in how much they can lock down.
92 The amount of memory that a single process can
94 is limited by both the per-process
96 resource limit and the
100 .Va vm.max_user_wired .
101 .Va vm.max_user_wired
102 applies to the system as a whole, so the amount available to a single
103 process at any given time is the difference between
104 .Va vm.max_user_wired
106 .Va vm.stats.vm.v_user_wire_count .
109 .Va security.bsd.unprivileged_mlock
110 is set to 0 these calls are only available to the super-user.
114 If the call succeeds, all pages in the range become locked (unlocked);
115 otherwise the locked status of all pages in the range remains unchanged.
123 .Va security.bsd.unprivileged_mlock
124 is set to 0 and the caller is not the super-user.
126 The address range given wraps around zero.
128 Some portion of the indicated address range is not allocated.
129 There was an error faulting/mapping a page.
130 Locking the indicated range would exceed the per-process or system-wide limits
139 .Va security.bsd.unprivileged_mlock
140 is set to 0 and the caller is not the super-user.
142 The address range given wraps around zero.
144 Some or all of the address range specified by the addr and len
145 arguments does not correspond to valid mapped pages in the address space
148 Locking the pages mapped by the specified range would exceed a limit on
149 the amount of memory that the process may lock.
166 system calls first appeared in
169 Allocating too much wired memory can lead to a memory-allocation deadlock
170 which requires a reboot to recover from.
172 The per-process and system-wide resource limits of locked memory apply
173 to the amount of virtual memory locked, not the amount of locked physical
175 Hence two distinct locked mappings of the same physical page counts as
176 2 pages aginst the system limit, and also against the per-process limit
177 if both mappings belong to the same physical map.
179 The per-process resource limit is not currently supported.