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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 pages or via nested
83 calls on the same address range.
84 Unlocking is performed explicitly by
86 or implicitly by a call to
88 which deallocates the unmapped address range.
89 Locked mappings are not inherited by the child process after a
92 Since physical memory is a potentially scarce resource, processes are
93 limited in how much they can lock down.
94 The amount of memory that a single process can
96 is limited by both the per-process
98 resource limit and the
104 applies to the system as a whole, so the amount available to a single
105 process at any given time is the difference between
108 .Va vm.stats.vm.v_wire_count .
111 .Va security.bsd.unprivileged_mlock
112 is set to 0 these calls are only available to the super-user.
116 If the call succeeds, all pages in the range become locked (unlocked);
117 otherwise the locked status of all pages in the range remains unchanged.
125 .Va security.bsd.unprivileged_mlock
126 is set to 0 and the caller is not the super-user.
128 The address given is not page aligned or the length is negative.
130 Locking the indicated range would exceed the system limit for locked memory.
132 Some portion of the indicated address range is not allocated.
133 There was an error faulting/mapping a page.
134 Locking the indicated range would exceed the per-process limit for locked
143 .Va security.bsd.unprivileged_mlock
144 is set to 0 and the caller is not the super-user.
146 The address given is not page aligned or the length is negative.
148 Some or all of the address range specified by the addr and len
149 arguments does not correspond to valid mapped pages in the address space
152 Locking the pages mapped by the specified range would exceed a limit on
153 the amount of memory that the process may lock.
170 system calls first appeared in
173 Allocating too much wired memory can lead to a memory-allocation deadlock
174 which requires a reboot to recover from.
176 The per-process resource limit is a limit on the amount of virtual
177 memory locked, while the system-wide limit is for the number of locked
179 Hence a process with two distinct locked mappings of the same physical page
180 counts as 2 pages against the per-process limit and as only a single page
183 The per-process resource limit is not currently supported.