Re: Video subsystem draft

[Vesa Jääskeläinen]

Yoshinori K. Okuji wrote:
> On Saturday 26 November 2005 01:28 am, Vesa Jääskeläinen wrote:
>>> Compression might make the performance horrible, because PPF is very
>>> optimized.
>> When there is a caching implemented in a one day, it's only initial
>> cost. So far I haven't seen performance problems with this. But then
>> again I haven't tried it too much.
> 
> I must test it myself, too. The performance of reading a compressed file is 
> slow, because of seeking. Seeking forward is fast, but seeking backward is 
> very slow. So compression makes sense for OS images, but not much for font 
> files.

> The most important part is the initial cost, BTW. Since a boot loader must be 
> quick to start up (otherwise, the user loses some seconds every time), 
> caching is not so important.

There is this transparent gzip support in gz file open, that diagnoses
file to decide wether it is gzipped or not. If there is transparent
option specified, it can also read nongzipped files. This would allow
user to pack font file if there is a need to compress it (of course with
cost of speed)

If I remember correctly I also saw caching of sectors in disk code, so
basicly if disk cache is big enough old font data will already be in
memory. And this will only cause little delay as there is no I/O
latency. Actual testing in real hardware will tell how good this is. I
am currently only running this on vmware.