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Disadvantage of background processes


 
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# 1  
Old 07-27-2009
Disadvantage of background processes

Hi,

Inorder to improve the performance, I am trying to execute my command as a background process..

For eg: To zip large numbers of files present in a directory instead of using a single process, i do follow the below method:

gunzip -c [source_file] > [destination_path]/[zip_file_name] &
--------------------------------------------------------------
Plz tell me about the disadvantages of the above method... I mean in terms of memory and other related stuffs...

Thanks in advance,
Unni
# 2  
Old 08-01-2009
Normally, to run a command, the shell will fork, that is, it makes a copy of itself. Both copies start to run they both know which is the parent and which is the child. The parent simply waits for the child to finish. The child overlays irself (via the exec() feature) with the disired program. It runs and (we hope) eventually finishes by calling exit. The parent then starts running again and it issues another prompt.

The main difference with a background process it that the parent does not wait. If you need to use that file you are unzipping as input for your next command, then putting the unzip in the background would be inconvienent. You would have to keep checking to see if its done. But if you have another task then there is no problem.

Once you have one program in the background, you could overdo it. Put 25 unzips in the background and the system will slow down. So don't do that.

Some programs want to ask you questions and have you type in answers. Don't put those in the background, they're not suitable background tasks.
# 3  
Old 08-04-2009
Hi Perderabo... Thanks for your valuable comment...

My case is like... I have to zip hundreds of big sized files... So if I'm doing as background processes, in the worst case this method would invoke that much process... which will definitely slow down my system...

So I preferred not to invoke the above command as background...
# 4  
Old 08-04-2009
Adding more processes only gets more done if you have disk throughput and CPU power you're not currently using. Zip doesn't cap either(except that it only uses one CPU), so it must be running up against one or the other limit already. If you have a fast modern computer, its probably limited by disk speed more than anything.
 

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