> > > > > > But quite often if DMA fails for some reson it will > > > > > > try to fall back to PIO something working slowly > > > > > > can be better than not working at all. > > > > > Is it always useful (even for the small data transfer) to use DMA ? > > > > > > > > for small transfere it can have the same over head to set up > > > > the dma transfere as it does to transfere the data in a case > > > > like this there it no point in using DMA > > > > > > But remember disks are always accessed in terms of blocks and they are > > > 512 bytes. Thus the question stands, is DMA setup faster than sending > > > 512 bytes to the bus? > > > > who said anything about a disk ? > > what about sending a small packet to a nic ? > > or some other information somewhere else > > Well, yes. So we could ask what is the critical size to use DMA... again that really goes back to a hardware specific as some hardware can be easyier / less overhead to setup a DMA transfere than others. i think it really comes down to which ever is fastest for the specific hardware and its current events. -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
