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28 .\" @(#)mlock.2 8.2 (Berkeley) 12/11/93
29 .\" $FreeBSD: src/lib/libc/sys/mlock.2,v 1.6.2.5 2001/12/14 18:34:01 ru Exp $
30 .\" $DragonFly: src/lib/libc/sys/mlock.2,v 1.4 2006/02/17 19:35:06 swildner Exp $
38 .Nd lock (unlock) physical pages in memory
45 .Fn mlock "const void *addr" "size_t len"
47 .Fn munlock "const void *addr" "size_t len"
52 locks into memory the physical pages associated with the virtual address
60 call unlocks pages previously locked by one or more
65 parameter should be aligned to a multiple of the page size.
68 parameter is not a multiple of the page size, it will be rounded up
70 The entire range must be allocated.
74 call, the indicated pages will cause neither a non-resident page
75 nor address-translation fault until they are unlocked.
76 They may still cause protection-violation faults or TLB-miss faults on
77 architectures with software-managed TLBs.
78 The physical pages remain in memory until all locked mappings for the pages
80 Multiple processes may have the same physical pages locked via their own
81 virtual address mappings.
82 A single process may likewise have pages multiply-locked via different virtual
83 mappings of the same pages or via nested
85 calls on the same address range.
86 Unlocking is performed explicitly by
88 or implicitly by a call to
90 which deallocates the unmapped address range.
91 Locked mappings are not inherited by the child process after a
94 Since physical memory is a potentially scarce resource, processes are
95 limited in how much they can lock down.
99 a system-wide ``wired pages'' limit and
104 These calls are only available to the super-user.
108 If the call succeeds, all pages in the range become locked (unlocked);
109 otherwise the locked status of all pages in the range remains unchanged.
115 The caller is not the super-user.
117 The address given is not page aligned or the length is negative.
119 Locking the indicated range would exceed either the system or per-process
120 limit for locked memory.
122 Some portion of the indicated address range is not allocated.
123 There was an error faulting/mapping a page.
129 The caller is not the super-user.
131 The address given is not page aligned or the length is negative.
133 Some portion of the indicated address range is not allocated.
134 Some portion of the indicated address range is not locked.
149 functions first appeared in
152 The per-process resource limit is a limit on the amount of virtual
153 memory locked, while the system-wide limit is for the number of locked
155 Hence a process with two distinct locked mappings of the same physical page
156 counts as 2 pages against the per-process limit and as only a single page
159 The per-process resource limit is not currently supported.