Date: Fri, 11 Apr 2014 16:59:31 +0930 From: "Daniel O'Connor" <doconnor@gsoft.com.au> To: Hans Petter Selasky <hps@selasky.org> Cc: freebsd-usb@freebsd.org Subject: Re: USB 3 devices not reliably connecting at 5Gbps Message-ID: <ACC91511-A630-4262-AFE4-441AA154E405@gsoft.com.au> In-Reply-To: <53478D5B.3090205@selasky.org> References: <A9616810-7BD9-49FC-BFA7-44206E4CCAC1@gsoft.com.au> <53478D5B.3090205@selasky.org>
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--Apple-Mail=_A05482E1-A348-4B13-8583-CDAAB0EC7481 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=iso-8859-1 On 11 Apr 2014, at 16:06, Hans Petter Selasky <hps@selasky.org> wrote: > On 04/11/14 06:33, Daniel O'Connor wrote: >> Also, when it does connect at 5Gbps the speed seems quite slow - on = my laptop (with USB controller VID 0x8086 PID 0x9c31 - Lynx point I = think) I get 225MB/sec using libusb. On FreeBSD I get around 92MB/sec = although only after lowering(!!) the amount read per transfer. >=20 > FreeBSD sets an IRQ latency of 125us, while the others use the default = of 62.5us. Are you double buffering the USB transfers? The IRQ latency = can be changed by editing a macro in the XHCI driver: >=20 > #define XHCI_IMOD_DEFAULT 0x000003E8U /* 8000 IRQ/second */ >=20 > At a rate of 225MB/s you need around 2x32Kbyte of buffer and you need = to avoid short transfers. Interesting.. My test program looks like.. for (i =3D 0; i < EP_FDNREQ; i++) { usb_xf[i].xf =3D libusb_alloc_transfer(0); usb_xf[i].idx =3D i; usb_xf[i].done =3D 0; usb_xf[i].submitted =3D 0; p =3D malloc(EP_FDXFAMT); =09 libusb_fill_bulk_transfer(usb_xf[i].xf, h, EP_UDBUS, p, = EP_FDXFAMT, usbcb, &usb_xf[i], 10000); } I then submit all these and then have the call back log the speed (after = N transfers) and reissue the request. (I can send you the full code if you like) I find that on OSX if I have.. #define EP_FDXFAMT 32768 /* Number of bytes per = tranfer */ #define EP_FDNREQ 4 /* Number of request to = keep in flight */ I get 225MB/sec pretty much constantly, if I lower those values then the = transfer rate is much lumpier. With the same code I get 125MB/sec on FreeBSD. I tried fiddling the numbers to get more but that seems to be the = maximum. Curiously if I increase the number of bytes per transfer to 64k the = throughput drops to 86MB/sec. Lowering it to 16k gives 125MB/sec, 8k gives 62MB/sec. Finally, I ran systat -vmstat 1 while running the test and I see 4000 = IRQ/sec on the xhci device, not 8000 as your comment above would = suggest. -- Daniel O'Connor software and network engineer for Genesis Software - http://www.gsoft.com.au "The nice thing about standards is that there are so many of them to choose from." -- Andrew Tanenbaum GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C --Apple-Mail=_A05482E1-A348-4B13-8583-CDAAB0EC7481 Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc Content-Description: Message signed with OpenPGP using GPGMail -----BEGIN PGP SIGNATURE----- Comment: GPGTools - http://gpgtools.org iD8DBQFTR5nb5ZPcIHs/zowRAg6EAKCf7Bya6rX4I1VfbXvozsMe8h/AegCgpwON sN9Y9BO/KidRxoOMUFjSX64= =6Lrl -----END PGP SIGNATURE----- --Apple-Mail=_A05482E1-A348-4B13-8583-CDAAB0EC7481--
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