squeeze(1)

NAME
     squeeze - squeeze memory from the system

SYNOPSIS
     squeeze [flag] amount

DESCRIPTION
     squeeze will allocate a region of its virtual memory of a size given by
     its arguments, and lock that virtual memory down into real memory, thus
     making it unavailable to other processes.  It can only be used by the
     superuser.

     The amount of memory locked is specified as an integer argument, in units
     given by the flag argument.  By default it is in megabytes (-m flag).  A
     flag of -p, implies that the amount is in pages; a flag of -k implies
     that the amount in kilobytes; and a flag of -% implies a percentage of
     the installed memory.

     Once the memory is locked down, squeeze prints a message on stdout saying
     how much is locked, and sleeps indefinitely.  It can be interrupted by
     SIGINT or SIGTERM, at which time it frees up the memory and exits.  The
     user should wait until after this message is printed before doing any
     experiments.

USAGE
     squeeze can be used to determine the approximate working set of a
     program.  To do so, use a machine which has enough physical memory to
     allow your target application to run without any paging (other than
     startup).  This can be determined by using the command ssusage to spawn
     your application.  When the application exits, its resource usage is
     printed; the value labeled majf gives the number of major page faults,
     that is the number of faults that required a physical read to satisfy.
     When run on a machine with a large amount of physical memory, this value
     is the number of faults needed to start the program, which is the minimum
     number for any run.

     Then run squeeze to lock down varying amounts of memory, and rerun the
     program.  The major-fault number will remain low at first, but as you
     squeeze out more and more memory, it will rise.  The amount of physical
     memory in the system minus the amount of memory squeezed at point at
     which your application begins to page-fault tells you the combined
     working set of your program, the kernel, and all other applications you
     normally have running.  If you have previously done this on a program
     whose paging behavior is well understood, you can determine the working
     set of the kernel and your normal environment, and by subtraction, the
     working set of the application you are studying.

     One program that can be used for this purpose is thrash(1).  It allocates
     a large block of memory, and then sequentially accesses each page in the
     block.  For all practical purposes, the working set of this program is
     the size of the memory allocated.
SEE ALSO
     ssusage(1), thrash(1)