HP-UX Reference (11i v1 00/12) - 2 System Calls (vol 5)

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mlockall(2) mlockall(2)

NAME

mlockall() - lock a process virtual address space in memory

SYNOPSIS

#include <sys/mman.h>

int mlockall( constant int flags);

DESCRIPTION

The mlockall() system call allows the calling process to lock its entire virtual address space into

memory, making it immune to all routine swapping.

ﬂags may be one or both of the following:

MCL_CURRENT Lock the current process virtual address space. All addressable pages of the

address space are locked.

MCL_FUTURE Lock any future additions to the process virtual address space.

Note that MCL_FUTURE does not imply MCL_CURRENT .

munlockall() or munlock() can be used to unlock all or a portion of the address space locked with

mlockall(). A single call to munlockall() removes all locks from the process virtual address space.

munlock() call results in only the speciﬁed pages being unlocked.

Regardless of how many times a process locks a page, a single munlock() or munlockall() will

unlock it.

When memory is shared by multiple processes and mlocks are applied to the same physical page by multi-

ple processes, a page remains locked until the last lock is removed from that page.

Locks and

MCL_FUTURE applied with mlockall() are not inherited by a child process.

The effective user ID of the calling process must be a superuser or the user must be a member of a group

that has the MLOCK privilege (see getprivgrp(2) and setprivgrp(1M)).

Although plock() and the mlock() family of functions may be used together in an application, each

may affect the other in unexpected ways. This practice is not recommended.

RETURN VALUE

mlockall() returns the following values:

0 Successful completion.

-1 Failure. The requested operation is not performed. errno is set to indicate the error.

ERRORS

mlockall() fails, errno is set to one of the following values:

[EINVAL] The flags ﬁeld did not contain either MCL_CURRENT and/or MCL_FUTURE .

[EAGAIN] There is not enough lockable memory in the system to satisfy the locking request.

[EPERM] The effective user ID of the calling process is not a superuser and the user does not

belong to a group that has the MLOCK privilege.

EXAMPLES

The following call to mlockall() locks the entire process virtual address space in memory and ensures

that any future additions to the address space will also be locked in memory:

mlockall( (MCL_CURRENT | MCL_FUTURE) );