Well, there *is* a bit of history on these package sizes. Now, having had frequent communication with you: 4kB is an effect of system page sizes. For more detail, see x300_impl.hpp's comments on X300_PCIE_RX_DATA_FRAME_SIZE. But: you're right, this is a communicated transport property, but since you basically know what you're doing (and know what to revert when things break), go ahead and modify things within the limits of what's stated in said comment.
Best regards, Marcus On Mon, 2018-09-24 at 20:20 +0000, Eugene Grayver wrote: > Yep, that's what seems to be the case. The whole point of PCIe is > lower latency -- with a frame size that large I can get lower latency > w/ 10 GbE and 500B frame size. I can't imagine it is a large effort > to get that fixed :) > > > _______________________ > Eugene Grayver, Ph.D. > Aerospace Corp., Principal Eng. > Tel: 310.336.1274 > ________________________ > > -----Original Message----- > From: Marcus Müller [mailto:[email protected]] > Sent: Monday, September 24, 2018 11:41 AM > To: Eugene Grayver <[email protected]>; > [email protected] > Subject: Re: [USRP-users] PCIe driver frame size > > Hi Eugene, > > I'm not an expert on the PCIe transport, but as far as I can tell > from 3.11.0.1's > > uhd::transport::muxed_zero_copy_if::sptr make_muxed_pcie_msg_xport > > the PCIe frame sizes seem to be immutable (4 kB, in fact, which, > subtracting header and dividing by sample bitwidth, leads to 1020 > samples per frame). > > Best regards, > Marcus > > On Fri, 2018-09-21 at 18:32 +0000, Eugene Grayver via USRP-users > wrote: > > Is there a way to specify the frame size on the PCIe > > interface? I > > tried using the same keywords as for the NIC, but it had no effect. > > I need low-latency and the default frame size is 5000 bytes (much > > too > > large for my needs). > > > > _______________________ > > Eugene Grayver, Ph.D. > > Aerospace Corp., Principal Eng. > > Tel: 310.336.1274 > > ________________________ > > > > _______________________________________________ > > USRP-users mailing list > > [email protected] > > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > > _______________________________________________ USRP-users mailing list [email protected] http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
