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Mastering Embedded Linux Development
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A page fault occurs when an application reads or writes to memory that is not committed to physical memory. It is impossible (or very hard) to predict when a page fault will happen, so they are another source of non-determinism in computers.
Fortunately, there is a function that allows you to commit all the memory used by the process and lock it down so that it cannot cause a page fault. It is mlockall(2)
. These are its two flags:
MCL_CURRENT
: Locks all pages currently mapped.MCL_FUTURE
: Locks pages that are mapped in later.You usually call mlockall
during the startup of the application with both flags set to lock all current and future memory mappings.
TIP
MCL_FUTURE
is not magic, in that there will still be a non-deterministic delay when allocating or freeing heap memory using malloc()/free()
or mmap()
. Such operations are best done at startup and not in the main control loops.
Memory allocated on the...