Search This Blog

Thursday, October 19, 2006


Most of people (even Klauss Knopper [1]) think that swap partition has better performance compare to swapfile (Ok. Most of people don't know what is swap file or swap partition ;). However, it isn't true, at least for 2.6 linux kernel. Check thread at Linux-Kernel Mailing list [ 2]. I think the most important is the 3rd point
Does creating the swapfile on a journaled filesystem (e.g. ext3 or reiser) incur a significant performance hit?
and answer
None at all. The kernel generates a map of swap offset -> disk blocks at swapon time and from then on uses that map to perform swap I/O directly against the underlying disk queue, bypassing all caching, metadata and filesystem code.
[1] Klaus Knopper, "Questions and Answers", Linux Magazine Polish ed., 3(25) March 2006, pp 38-40.
[2] Andre Morton et al., "Swap partition vs swap file" thread Linux-Kernel Mailing List, July 2005.

Saturday, October 07, 2006 v2

I rewrite my script for converting raw format pictures. Now, it is converting files from raw to jpg in loop. Doing first convert of all raw files take a lot of space (ppm files are BIG). Right now I need space for one ppm file. Morover, ppm->jpg converting and resizing are made in one step. I found very nice perl program (ExifTool) to managing exif info.

for raf in *.raf
        dcraw -w $raf
        name=`basename $raf .raf`
        jpg=`basename $name`.jpg
        ppm=`basename $name`.ppm
        echo $name
        convert -resize 800x600 $ppm $jpg
        $EXIFPATH/exiftool -TagsFromFile $raf $jpg
        rm $ppm $jpg"_original"

Tuesday, October 03, 2006

Overwriting a line in Vim

Finally, I've learn how to overwrite the whole line in Vim. First you have to yank the line you would like to copy (yy), next to mark the destination line (V) and paste the first line (P or p on it), what gives VP. I found it here.