URGENT Help required regarding the use of FORK system call Post: 8103

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Top Forums UNIX for Advanced & Expert Users URGENT Help required regarding the use of FORK system call Post 8103 by kkumar1975 on Friday 5th of October 2001 01:41:36 PM

10-05-2001

Registered User

URGENT Help required regarding the use of FORK system call

I desperately wanted one of the UNIX Gurus to help me resolve my problem asap(I have to deliver the code to the client by Monday 08-oct).

I have a file with around 5 million records (50 lakhs). Now my original process was taking around 30 hours to read the complete file, process each and every record and write it to another file. we do a lot of calculations for each and every record so it takes that time.

Now I planned to implement PARALLEL processing in my program. So I am dividing the complete input file into 5 chunks (each of 1 million) and sending every chunk to every child process to process. Now every child process will process its own chunk and write it to its own temporary file. Finally in the parent process I am planning to merge all the temporary files together. By doing this I believe I shall save a lot of processing time.

What I am basically interested to know is that what are the side effects of using FORK in the C programs? Are there any SYSTEM level impacts by using FORK? Is there any system call to merge multiple files into ONE? I am interested in knowing what happens if a Child is killed? How can I reprocess the child that is killed? How do I ensure that there are no ZOMBIES or INFANT process created?

Can some one briefly advise how I can proceed with my Logic. I have already written the logic but I want to cross check if there is something I am missing in my logic.

Thanks,
Kumar

kkumar1975

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fork

FORK(2) 						     Linux Programmer's Manual							   FORK(2)

NAME

       fork - create a child process

SYNOPSIS

       #include <sys/types.h>
       #include <unistd.h>

       pid_t fork(void);

DESCRIPTION

       fork  creates a child process that differs from the parent process only in its PID and PPID, and in the fact that resource utilizations are
       set to 0.  File locks and pending signals are not inherited.

       Under Linux, fork is implemented using copy-on-write pages, so the only penalty incurred by fork is the time and memory required to  dupli-
       cate the parent's page tables, and to create a unique task structure for the child.

RETURN VALUE

       On success, the PID of the child process is returned in the parent's thread of execution, and a 0 is returned in the child's thread of exe-
       cution.	On failure, a -1 will be returned in the parent's context, no child process will be created, and errno will be set appropriately.

ERRORS

       EAGAIN fork cannot allocate sufficient memory to copy the parent's page tables and allocate a task structure for the child.

       ENOMEM fork failed to allocate the necessary kernel structures because memory is tight.

CONFORMING TO

       The fork call conforms to SVr4, SVID, POSIX, X/OPEN, BSD 4.3.

SEE ALSO

       clone(2), execve(2), vfork(2), wait(2)

Linux 1.2.9							    1995-06-10								   FORK(2)