mlock munlock - lock (unlock) physical pages in memory
system call, the indicated pages will cause neither a non-resident page nor address-translation fault until they are unlocked. They may still cause protection-violation faults or TLB-miss faults on architectures with software-managed TLBs. The physical pages remain in memory until all locked mappings for the pages are removed. Multiple processes may have the same physical pages locked via their own virtual address mappings. A single process may likewise have pages multiply-locked via different virtual mappings of the same pages or via nested mlock ();
calls on the same address range. Unlocking is performed explicitly by munlock ();
or implicitly by a call to munmap ();
which deallocates the unmapped address range. Locked mappings are not inherited by the child process after a fork(2).
Since physical memory is a potentially scarce resource, processes are
limited in how much they can lock down.
A single process can
the minimum of a system-wide ``wired pages'' limit and the per-process RLIMIT_MEMLOCK resource limit.
These calls are only available to the super-user.
If the call succeeds, all pages in the range become locked (unlocked); otherwise the locked status of all pages in the range remains unchanged.
system call will fail if:
The per-process resource limit is a limit on the amount of virtual memory locked, while the system-wide limit is for the number of locked physical pages. Hence a process with two distinct locked mappings of the same physical page counts as 2 pages against the per-process limit and as only a single page in the system limit.
The per-process resource limit is not currently supported.
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Created 1996-2021 by Maxim Chirkov
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