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Re: require sugesstions for writing a perl script

by bart (Canon)
on Mar 06, 2013 at 11:44 UTC ( #1021997=note: print w/ replies, xml ) Need Help??

in reply to require sugesstions for writing a perl script

So what is the cause of the slowness of each individual script? Is it CPU, disk I/O, or waiting for external resources (for example, waiting for a file download) that takes most time?

If it's either CPU, harddisk access or database access that causes the slowness, then I would recommend against doing hem in parallel. 2 disk simultaneous hard disk accesses on the same disk will actually be slower than doing them one at a time, because the disk head has to constantly switch between the head positions for the 2 files. Likewise, doing 2 CPU intensive processes in parallel on the same CPU will not be faster than doing them one at a time, it'll only use more RAM.

If you're waiting for a file download to complete, you could have it do a few at a time. Also, if it's a combination of the above factors, you could get a speed gain doing them in parallel, for example one process could be accessing the disk while another is doing a computation.

Thus: do a benchmark test, limit the number of parallel processes, and see if it is actually faster, or not.

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