Help optimizing sort of large files Post: 302925218

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Top Forums UNIX for Advanced & Expert Users Help optimizing sort of large files Post 302925218 by Corona688 on Friday 14th of November 2014 03:04:46 PM

11-14-2014

Registered User

Quote:

Originally Posted by kogorman3

In testing, the gain was real but not big. The elephant in the room here seems to be the number of passes, and I/O time is a large percent of the total. While threading improves overlap, they're still competing for use of the same input and output files and directories.

I know. I am concerned you might be making your buffers too large -- ideal settings for 1 process would be twice what your computer can handle when doubled. Halve the buffer size and number of files every time you double the number of threads. Individually their efficiency could go down a bit, but collectively they can get masses more work done if you have enough cache to keep up with them.

You might look into increasing the writeback time on your temp partition. Spending all your I/O time writing changes that are going to be invalidated 60 seconds later could be a waste, let the disk cache do the thrashing.

Which means leaving some RAM for disk cache of course. Using all available RAM forces it to do more I/O. 50/50 for sort vs cache might be a good split off the cuff.

I wonder if your SSD might be a better temp folder than swap -- like you say, you're not using it, and forcing your system to eat into swap can really interfere with caching. An ssd could support a much larger number of streams, potentially.

Last edited by Corona688; 11-14-2014 at 04:14 PM..

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HTCACHECLEAN(8) 						   htcacheclean 						   HTCACHECLEAN(8)

NAME

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       htcacheclean [ -D ] [ -v ] [ -t ] [ -r ] [ -n ] -ppath -llimit

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       -D     Do a dry run and don't delete anything. This option is mutually exclusive with the -d option.

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