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Full Discussion: Help optimizing sort of large files
Top Forums UNIX for Advanced & Expert Users Help optimizing sort of large files Post 302925455 by Corona688 on Monday 17th of November 2014 10:10:34 AM
Old 11-17-2014
Quote:
Originally Posted by kogorman3
Defragged? I'm not sure how to do that on Linux, so I am using a fresh 2-TB drive formatted ext4 and directing sort to use it for temporaries. It's otherwise empty.
ext4 partitions are relatively easy to defrag, being designed with runtime defragmentation in mind (yes, runtime -- no need to unmount) via the e4defrag utility. There's no point defragging an empty partition, but check that your input and output partitions aren't a mess after all this testing.
Quote:
I've got 32 GB RAM and a 64-bit CPU. That's big enough for the whole test file, but the parameters to sort don't let it work that way.
The process of merge-sorting doesn't work that way. No matter how big your buffers are, it has to do the same number of merges on the same number of elements of the same sizes, nearly all of them tiny... Starting with billions of 2-element merges, half the number of 4-element merges, etc, etc, etc. (A little oversimplification, but the merging options don't substantially change this.) That's why pushing buffers to ridiculous sizes is so little help -- they're nearly always dead weight except for the final merge, when it's never going to be big enough to matter anyway.
Last edited by Corona688; 11-17-2014 at 11:17 AM..
 

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LEARN ABOUT CENTOS

e4defrag

E4DEFRAG(8)						      System Manager's Manual						       E4DEFRAG(8)

NAME

       e4defrag - online defragmenter for ext4 filesystem

SYNOPSIS

       e4defrag [ -c ] [ -v ] target ...

DESCRIPTION

       e4defrag  reduces  fragmentation  of  extent  based file. The file targeted by e4defrag is created on ext4 filesystem made with "-O extent"
       option (see mke2fs(8)).	The targeted file gets more contiguous blocks and improves the file access speed.

       target is a regular file, a directory, or a device that is mounted as ext4 filesystem.  If target is a directory, e4defrag reduces fragmen-
       tation  of all files in it. If target is a device, e4defrag gets the mount point of it and reduces fragmentation of all files in this mount
       point.

OPTIONS

       -c     Get a current fragmentation count and an ideal fragmentation count, and calculate fragmentation score based on them. By seeing  this
	      score, we can determine whether we should execute e4defrag to target.  When used with -v option, the current fragmentation count and
	      the ideal fragmentation count are printed for each file.

	      Also this option outputs the average data size in one extent. If you see it, you'll find the file has ideal  extents  or	not.  Note
	      that the maximum extent size is 131072KB in ext4 filesystem (if block size is 4KB).

	      If this option is specified, target is never defragmented.

       -v     Print error messages and the fragmentation count before and after defrag for each file.

NOTES

       e4defrag  does  not  support swap file, files in lost+found directory, and files allocated in indirect blocks. When target is a device or a
       mount point, e4defrag doesn't defragment files in mount point of other device.

       Non-privileged users can execute e4defrag to their own file, but the score is not printed if -c	option	is  specified.	Therefore,  it	is
       desirable to be executed by root user.

AUTHOR

       Written by Akira Fujita <a-fujita@rs.jp.nec.com> and Takashi Sato <t-sato@yk.jp.nec.com>.

SEE ALSO

       mke2fs(8), mount(8).

e4defrag version 2.0						     May 2009							       E4DEFRAG(8)
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