On Fri, Oct 29, 2004, Duncan Sands <[EMAIL PROTECTED]> wrote: > > It probably will be significantly less. We have buffer size issues with > > usbfs and libusb. > > > > Older versions of libusb used the synchronous bulk read/write calls and > > those were limited to a page size. We've since switched to using > > asynchronous, URB based calls, which allow us buffer sizes of up to > > 16KB, but I think that will still limit us to quite a bit under 30MB/s. > > > > We can go even further by using multiple URBs and queuing them, but > > libusb doesn't currently do that. > > Hi Johannes, maybe it should allocate multiple pages and then use scatter-gather > io out of them. That avoids having to allocate large contiguous lumps of kernel > memory, and should also be good for performance.
Are you talking about exporting scatter-gather via usbfs? Or having the kernel avoid a copy from userspace by using scatter-gather internally? The former might be useful, but only if the application really goes out of the way to use it. The latter sounds good, but might be tricky. Scatter-gather implies properly sized buffers to ensure the correct packetization, which I don't think userspace could guarantee. 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
