Hello Alain, just a general hint in benchmarking (for beginners):
a) try to measure something with something that you understand what it does; else your measurements might not be interpretable scince you don't know what rawspeed does (*exactly*), or what your indexing app does (again, *exctly), interpratation might be hard. choose an application that you really understand; maybe by writing some 100 lines of code where you *know* what they do at least for Jack's 'unzip 2 GB file* it's clear what it does: it writes a single, real big file, most probably in big chunks (but even that is unknown) b) compare apples to apples the reason for any speed difference may dependend on many things like OS: buffering strategy, cache replacement strategy, cache size,... APP: write size, alignment (see below),... UMB, and possibly the reason for the real slowdown: I know that Freedos won't read data directly into a UMB destination; these data are read single-sectorwise through a buffer loaded in low RAM (that's at least what I remember to have implemented). this IS slow. the reason for this is, that UMBPCI was/is popular for freedos as UMB provider, and reading with DMA to UMB area wouldn't work on a significant subset of all machines. while this was DMA for floppies, this is probably still true for UDMA, as it's a UMBPCI+chipset problem so we (I and Bart agreed) decided to read everything above 0xa000 through this single deblocking buffer. so it comes down to: if anybody read's data directly into UMB (using int21 or int25/26), this will be slow; usually this uncommon HTH re:UDMA and alignment 'problem' just by aligning read buffers proper to 32 bit boundaries, I could gain ~10% total performance. reason: with proper alignment, UDMA can read directly into my user buffers, else it has to read+copy to/from XMS. 'caused' by UDMA, but it's certainly not UDMA to blame. it's just that UDMA works best if you follow the rules; if not you have to pay some performance tom ------------------------------------------------------- SF.Net email is sponsored by: Discover Easy Linux Migration Strategies from IBM. Find simple to follow Roadmaps, straightforward articles, informative Webcasts and more! Get everything you need to get up to speed, fast. http://ads.osdn.com/?ad_id=7477&alloc_id=16492&op=click _______________________________________________ Freedos-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freedos-devel
