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Full Discussion: Shared memory in linux
Operating Systems Linux Red Hat Shared memory in linux Post 302404518 by jim mcnamara on Tuesday 16th of March 2010 05:50:55 PM
Old 03-16-2010
Shared memory is physical memory that is used by two or more different processes at the same time.

Ex: shared libraries. This is code that gets loaded into memory, and all processes running on the system see it an use it at the same time.
 

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serialize(2)							System Calls Manual						      serialize(2)

NAME
serialize() - force target process to run serially with other processes SYNOPSIS
DESCRIPTION
The system call is used to force the target process referenced by the pid value passed in to run serially with other processes also marked for serialization. If the value of pid is zero, then the currently running process is marked for serialization. Once a process has been marked by the process stays marked until process completion, unless is reissued on the serialized process with timeshare set to 1. If timeshare is set to 1, the process specified in pid will be returned to normal timeshare scheduling algorithms. This call is used to improve process throughput since process throughput usually increases for large processes when they are executed seri- ally instead of allowing each program to run for only a short period of time. By running large processes one at a time, the system makes more efficient use of the CPU as well as system memory, since each process does not end up constantly faulting in its working set, to only have the pages stolen when another process starts running. As long as there is enough memory in the system, processes marked by behave no differently from other processes in the system. However, once memory becomes tight, processes marked by are run one at a time with the highest priority processes being run first. Each process runs for a finite interval of time before another serialized process is allowed to run. RETURN VALUE
returns zero upon successful completion, or nonzero if the system call failed. ERRORS
If fails, it sets (see errno(2)) to the following value: The pid passed in does not exist. WARNINGS
The user has no way of forcing an execution order on serialized processes. AUTHOR
was developed by HP. SEE ALSO
serialize(1), privileges(5). serialize(2)
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