[Python-Dev] PEP 393 review (original) (raw)

Antoine Pitrou solipsis at pitrou.net
Sun Aug 28 22:27:20 CEST 2011

Le dimanche 28 août 2011 à 22:23 +0200, "Martin v. Löwis" a écrit :

Am 28.08.2011 22:01, schrieb Antoine Pitrou: > >> - the iobench results are between 2% acceleration (seek operations), >> 16% slowdown for small-sized reads (4.31MB/s vs. 5.22 MB/s) and >> 37% for large sized reads (154 MB/s vs. 235 MB/s). The speed >> difference is probably in the UTF-8 decoder; I have already >> restored the "runs of ASCII" optimization and am out of ideas for >> further speedups. Again, having to scan the UTF-8 string twice >> is probably one cause of slowdown. > > I don't think it's the UTF-8 decoder because I see an even larger > slowdown with simpler encodings (e.g. "-E latin1" or "-E utf-16le").

But those aren't used in iobench, are they?

I was not very clear, but you can change the encoding used in iobench by using the "-E" command-line option (while UTF-8 is the default if you don't specify anything).

For example:

$ ./python Tools/iobench/iobench.py -t -E latin1 Preparing files... Text unit = one character (latin1-decoded)

** Text input **

[ 400KB ] read one unit at a time... 5.17 MB/s [ 400KB ] read 20 units at a time... 77.6 MB/s [ 400KB ] read one line at a time... 209 MB/s [ 400KB ] read 4096 units at a time... 509 MB/s

[ 20KB ] read whole contents at once... 885 MB/s [ 400KB ] read whole contents at once... 730 MB/s [ 10MB ] read whole contents at once... 726 MB/s

(etc.)

Regards

Antoine.

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