On Mon, Apr 26, 2010 at 04:27:46PM +0530, B.Vinai Kumar wrote: > Hi All, > > I'am trying to implement zero copy in USBIP while sending / receiving > usbip packets. > > I started it with send path. The device which I used is mass storage. > I'am using linux kernel 2.6.15. 2.6.15 is _very_ old, and not supported by anyone. You might try this on a more modern kernel release, like 2.6.33 or newer. > After virtualization, once the file copy starts from device to pc each > usbip packet carries payload of 64K. > > I'am allocating this 64K buffer through __get_free_pages() (with order > 4) and assigning the buffer pointer to urb. After completion of URB > i'am trying to send this buffer page by page by using tcp_sendpage > instead of calling kernel_sendmsg(), this is to avoid copy which is > done in the TCP send path. > > By doing this way it is able to send the buffer successfully, but I'am > not finding the way to free this buffer. This copy continues until the > entire memory is consumed. After you are done with the memory, you need to explicitly free it, why can't you do that? > who will free this buffer? You need to. > 1) If i call free_pages for entire 64K right after tcp_sendpage (i.e > after sending all the pages, 64K). then observed > the Kernel panic. It is obvious that the tcp core is not yet finished its job. > > 2) TCP core is also not freeing these pages. > > This might be because, I allocated 64K buffer at once and trying to > free it page by page. > > I need some help to resolve this issue. > > Performance wise there is a huge jump in throughput. Are you sure? The bandwith issue should be on the usb device side, not the network from what I have seen. What type of device are you testing this with? thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
