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Top Forums UNIX for Advanced & Expert Users Help optimizing sort of large files Post 302925635 by Corona688 on Tuesday 18th of November 2014 10:50:31 AM
Old 11-18-2014
Quote:
Originally Posted by kogorman3
Size and number are linked. If they're bigger, there are fewer of them.
It doesn't work that way. It doesn't run 16384 individual merges simultaneously, then 4096 merges simultaneously, then 1024, etc etc. It always does the number you tell it to, as many times as it takes to process the list of things to do.

I don't think small sorts hurt you, especially since they're small enough to be cached. What hurts you are merges on too many files at once for the disk to seek between, reducing it's I/O throughput.

Remember you are trying to find a "sweet spot" where CPU use and disk throughput are both at peak -- where the system can sustain full disk and cpu use.

Quote:
True. I do not do anything to clear the caches before each run, but the tests are done by scripts that always do them in the same order, so I would expect more uniformity than I've seen so far.
Check if you're eating into swap sometimes. Hitting swap could have severe performance penalties that throw off your tests.
 

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SORT(1) 						      General Commands Manual							   SORT(1)

NAME
sort - sort a file of ASCII lines SYNOPSIS
sort [-bcdfimnru] [-tc] [-o name] [+pos1] [-pos2] file ... OPTIONS
-b Skip leading blanks when making comparisons -c Check to see if a file is sorted -d Dictionary order: ignore punctuation -f Fold upper case onto lower case -i Ignore nonASCII characters -m Merge presorted files -n Numeric sort order -o Next argument is output file -r Reverse the sort order -t Following character is field separator -u Unique mode (delete duplicate lines) EXAMPLES
sort -nr file # Sort keys numerically, reversed sort +2 -4 file # Sort using fields 2 and 3 as key sort +2 -t: -o out # Field separator is : sort +.3 -.6 # Characters 3 through 5 form the key DESCRIPTION
Sort sorts one or more files. If no files are specified, stdin is sorted. Output is written on standard output, unless -o is specified. The options +pos1 -pos2 use only fields pos1 up to but not including pos2 as the sort key, where a field is a string of characters delim- ited by spaces and tabs, unless a different field delimiter is specified with -t. Both pos1 and pos2 have the form m.n where m tells the number of fields and n tells the number of characters. Either m or n may be omitted. SEE ALSO
comm(1), grep(1), uniq(1). SORT(1)
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