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Top Forums UNIX for Dummies Questions & Answers Query on Running Multiple processes in background Post 302456591 by Corona688 on Friday 24th of September 2010 04:36:27 PM
Old 09-24-2010
Quote:
Originally Posted by gpta_varun
Thanks for the reply vbe !

But before I dwell further ,
I have some queries:

In case I run multiple processes from a script ,
1) Are all the processes allocated to a single CPU or multiple CPU ?
2) Can there be a possibility that a lot of time is wasted in scheduling the processes , allocated to single CPU?

3) In case of a fork() , are the child processes allocated to multiple CPUs for execution ? If not , can we do so ?
How should we know? We don't even know what OS is running on your server. This is important. Some have programmable restrictions in the number of CPU's it will let a user monopolize simultaneously.

Assuming there's not some sort of restrictions in place, multiple processes will run on multiple cores. But you know what they say about assumptions.

I don't see a lot of point running umpteen instances of RCP in parallel. The transfer's probably not CPU-bound, more likely being bottlenecked by disk or network, so more cores won't help. You'd have 9 transfers at X/9 MBPS instead of one transfer at X MBPS.
 

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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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