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32 .\" @(#)mlock.2 8.2 (Berkeley) 12/11/93
33 .\" $FreeBSD: src/lib/libc/sys/mlock.2,v 1.6.2.5 2001/12/14 18:34:01 ru Exp $
41 .Nd lock (unlock) physical pages in memory
48 .Fn mlock "const void *addr" "size_t len"
50 .Fn munlock "const void *addr" "size_t len"
55 locks into memory the physical pages associated with the virtual address
63 call unlocks pages previously locked by one or more
68 parameter should be aligned to a multiple of the page size.
71 parameter is not a multiple of the page size, it will be rounded up
73 The entire range must be allocated.
77 call, the indicated pages will cause neither a non-resident page
78 nor address-translation fault until they are unlocked.
79 They may still cause protection-violation faults or TLB-miss faults on
80 architectures with software-managed TLBs.
81 The physical pages remain in memory until all locked mappings for the pages
83 Multiple processes may have the same physical pages locked via their own
84 virtual address mappings.
85 A single process may likewise have pages multiply-locked via different virtual
86 mappings of the same pages or via nested
88 calls on the same address range.
89 Unlocking is performed explicitly by
91 or implicitly by a call to
93 which deallocates the unmapped address range.
94 Locked mappings are not inherited by the child process after a
97 Since physical memory is a potentially scarce resource, processes are
98 limited in how much they can lock down.
102 a system-wide ``wired pages'' limit and
107 These calls are only available to the super-user.
111 If the call succeeds, all pages in the range become locked (unlocked);
112 otherwise the locked status of all pages in the range remains unchanged.
118 The caller is not the super-user.
120 The address given is not page aligned or the length is negative.
122 Locking the indicated range would exceed either the system or per-process
123 limit for locked memory.
125 Some portion of the indicated address range is not allocated.
126 There was an error faulting/mapping a page.
132 The caller is not the super-user.
134 The address given is not page aligned or the length is negative.
136 Some portion of the indicated address range is not allocated.
137 Some portion of the indicated address range is not locked.
148 Unlike The Sun implementation, multiple
150 calls on the same address range require the corresponding number of
152 calls to actually unlock the pages, i.e.\&
155 This should be considered a consequence of the implementation
158 The per-process resource limit is a limit on the amount of virtual
159 memory locked, while the system-wide limit is for the number of locked
161 Hence a process with two distinct locked mappings of the same physical page
162 counts as 2 pages against the per-process limit and as only a single page
165 The per-process resource limit is not currently supported.
171 functions first appeared in