On Fri, Oct 29, 2004, Oliver Neukum <[EMAIL PROTECTED]> wrote: > Am Freitag, 29. Oktober 2004 20:44 schrieb David Brownell: > > On Friday 29 October 2004 11:13, Johannes Erdfelt wrote: > > > > If usbfs instead grabbed a bunch of non-contiguous > > > > pages, copied the data into them from user-space, and then sent it (using > > > > scatter-gather io), then there is no longer any memory pressure problem. > > > > What's more, there would also be no reason not to increase the maximum > > > > data size from 16k to something much bigger, say 256k. Allowing bigger > > > > buffers should increase performance. > > > > > > Duh, that would be the obvious way to increase performance and > > > reliability. > > > > > > Not to mention it should be relatively easy to implement. > > > > Yep, and you'd be able to clean up properly after an error in > > the middle of your N urbs ... the scatterlist code handles > > such things. > > > > Another tweak would be to remove the limit on transfer size. > > Use whatever algorithm you want to transfer the first chunk; > > for high speed, a scatterlist is *really* desirable. Then > > repeat for successive chunks ... until error, or all done. > > (And if you can't get enough buffers to use big chunks, then > > you could still make progress using smaller chunks...) > > I am afraid there is a problem. In fact, the current situation > cannot be allowed. There has to be a limit on the number > of URBs and buffers, or we allow any user to eat up all memory.
I'm ok with a limit and I agree that one is necessary. In reality, you reach a point of diminishing returns anyway. We just need to figure out roughly where that point is and set the limit accordingly. JE ------------------------------------------------------- This SF.Net email is sponsored by: Sybase ASE Linux Express Edition - download now for FREE LinuxWorld Reader's Choice Award Winner for best database on Linux. http://ads.osdn.com/?ad_id=5588&alloc_id=12065&op=click _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
