I am working on a driver for the CD Rom drive on the Sega Dreamcast (the so-called "GD Rom" drive). This device is electorically compatible with IDE-3 devices and has a pretty good match in terms of the control block registers but it implements its own packet command interface. I now have a working driver but the performance is lousy. The driver reads data off the disk using DMA and the target for the DMA has to be a contiguous. Therefore I have set: /* using DMA so memory will need to be contiguous */ blk_queue_max_hw_segments(gd.gdrom_rq, 1); /* set a large max size to get most from DMA */ blk_queue_max_segment_size(gd.gdrom_rq, 0x40000); ie only one segment per request but a big (for a small device) maximum size for the segment. A priori I can see no performance advantage in allowing each request to include multiple segments because then I'd only have to reshake them so they went in one at a time. But from the looks of it if I do set the maximum number of segments to 1 then each request is limited to the smallest size - ie what I set in blk_queue_hardsect_size. Is that right? What is the best way to go here? - To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
