Re: [Qemu-devel] [PATCH 1/7] usb: remove old usb-host code
On Fr, 2013-11-08 at 17:51 +0100, Jan Kiszka wrote: On 2013-11-08 16:39, Gerd Hoffmann wrote: Hi, OK, then here is the first issue I ran into while trying libusbx (git head, i.e. 1.0.17+: The new stack causes significant latency issues that makes it almost unusable for pass-through of USB audio devices (some headset in my case). Reverting usb-linux and disabling libusb over QEMU git head makes things work again. I'll have to stick with this for now as it is affecting my work environment. Any spontaneous ideas how to analyse or even resolve this? Try setting isobsize property to something smaller than 32 (which is the default). OK, isobsize=2 and isobufs=32 helped, possibly other combinations as well - but not just reducing isobsize or increasing isobufs. Any theory about this? How can we find better defaults? isobsize is the size of a single buffer (in MaxPacketSize units). isobufs is the number of buffers in the ring. So the total ring buffer size is MaxPacketSize * isobsize * isobufs. isobsize basically trades overhead for latency. Larger numbers reduce the overhead, smaller numbers reduce latency. isobufs should be as small as possible. Start with 4 (default). If you get overruns/underruns increase. We should probably look at the endpoint interval, then calculate how many packets we should expect within a certain time range and use that as additional factor for the buffer size. That should get the defaults closer to the actual needs of the device. cheers, Gerd
Re: [Qemu-devel] [PATCH 1/7] usb: remove old usb-host code
Hi, On 11/11/2013 09:47 AM, Gerd Hoffmann wrote: On Fr, 2013-11-08 at 17:51 +0100, Jan Kiszka wrote: On 2013-11-08 16:39, Gerd Hoffmann wrote: Hi, OK, then here is the first issue I ran into while trying libusbx (git head, i.e. 1.0.17+: The new stack causes significant latency issues that makes it almost unusable for pass-through of USB audio devices (some headset in my case). Reverting usb-linux and disabling libusb over QEMU git head makes things work again. I'll have to stick with this for now as it is affecting my work environment. Any spontaneous ideas how to analyse or even resolve this? Try setting isobsize property to something smaller than 32 (which is the default). OK, isobsize=2 and isobufs=32 helped, possibly other combinations as well - but not just reducing isobsize or increasing isobufs. Any theory about this? How can we find better defaults? isobsize is the size of a single buffer (in MaxPacketSize units). isobufs is the number of buffers in the ring. So the total ring buffer size is MaxPacketSize * isobsize * isobufs. isobsize basically trades overhead for latency. Larger numbers reduce the overhead, smaller numbers reduce latency. isobufs should be as small as possible. Start with 4 (default). If you get overruns/underruns increase. We should probably look at the endpoint interval, then calculate how many packets we should expect within a certain time range and use that as additional factor for the buffer size. That should get the defaults closer to the actual needs of the device. hw/usb/redirect.c actually has some code for that, you could use that as a start for the host redirection code... Regards, Hans
Re: [Qemu-devel] [PATCH 1/7] usb: remove old usb-host code
On 2013-10-09 13:42, Gerd Hoffmann wrote: Hi, Only very recent distros fulfill the need of = 1.0.13, so you naturally fall back to this code. I just realized that even the factory build of OpenSUSE is still on libusb-1.0.9. Current Ubuntu versions are on 1.0.12 at best. Didn't check others so far. Ouch. The 1.0.13 release is one year old by now. Fedora 19 is at 1.0.16 btw. So isn't this step a bit too early? There is always the 'git revert' option in case it turns out there are too many issues ... So what to do? Do you expect all the other distros to catch up regarding libusb until QEMU 1.7 is released? They will update once they figure this is needed for qemu 1.7 :) Updates will probably not yet be available at release time though. If we revert, thereby continue fallback to the old code, chances are high that nothing happens and we'll face the same issue for qemu 1.8. Given that there are some known issues in the host-linux code which are fixed in host-libusb I really want get rid of it. OK, then here is the first issue I ran into while trying libusbx (git head, i.e. 1.0.17+: The new stack causes significant latency issues that makes it almost unusable for pass-through of USB audio devices (some headset in my case). Reverting usb-linux and disabling libusb over QEMU git head makes things work again. I'll have to stick with this for now as it is affecting my work environment. Any spontaneous ideas how to analyse or even resolve this? Jan -- Siemens AG, Corporate Technology, CT RTC ITP SES-DE Corporate Competence Center Embedded Linux
Re: [Qemu-devel] [PATCH 1/7] usb: remove old usb-host code
Hi, OK, then here is the first issue I ran into while trying libusbx (git head, i.e. 1.0.17+: The new stack causes significant latency issues that makes it almost unusable for pass-through of USB audio devices (some headset in my case). Reverting usb-linux and disabling libusb over QEMU git head makes things work again. I'll have to stick with this for now as it is affecting my work environment. Any spontaneous ideas how to analyse or even resolve this? Try setting isobsize property to something smaller than 32 (which is the default). cheers, Gerd
Re: [Qemu-devel] [PATCH 1/7] usb: remove old usb-host code
On 2013-11-08 16:39, Gerd Hoffmann wrote: Hi, OK, then here is the first issue I ran into while trying libusbx (git head, i.e. 1.0.17+: The new stack causes significant latency issues that makes it almost unusable for pass-through of USB audio devices (some headset in my case). Reverting usb-linux and disabling libusb over QEMU git head makes things work again. I'll have to stick with this for now as it is affecting my work environment. Any spontaneous ideas how to analyse or even resolve this? Try setting isobsize property to something smaller than 32 (which is the default). OK, isobsize=2 and isobufs=32 helped, possibly other combinations as well - but not just reducing isobsize or increasing isobufs. Any theory about this? How can we find better defaults? Jan -- Siemens AG, Corporate Technology, CT RTC ITP SES-DE Corporate Competence Center Embedded Linux
Re: [Qemu-devel] [PATCH 1/7] usb: remove old usb-host code
On 2013-10-07 09:16, Gerd Hoffmann wrote: On Mi, 2013-10-02 at 15:14 +0200, Jan Kiszka wrote: On 2013-09-19 11:34, Gerd Hoffmann wrote: The usb-host code has been rewritten for qemu 1.5 to use libusb, the old code has been left in as temporary fallback. Now we are two releases further out, targeting the 1.7 release. No major issues with the new code poped up until now. Time to remove it from tre tree. Should we ever need it again for some reason -- git has a copy for us in the history. Well, maybe not many users were actually exploiting the new libusb code, thus were able to produce feedback. Only very recent distros fulfill the need of = 1.0.13, so you naturally fall back to this code. I just realized that even the factory build of OpenSUSE is still on libusb-1.0.9. Current Ubuntu versions are on 1.0.12 at best. Didn't check others so far. Ouch. The 1.0.13 release is one year old by now. Fedora 19 is at 1.0.16 btw. So isn't this step a bit too early? There is always the 'git revert' option in case it turns out there are too many issues ... So what to do? Do you expect all the other distros to catch up regarding libusb until QEMU 1.7 is released? Jan -- Siemens AG, Corporate Technology, CT RTC ITP SES-DE Corporate Competence Center Embedded Linux
Re: [Qemu-devel] [PATCH 1/7] usb: remove old usb-host code
Hi, Only very recent distros fulfill the need of = 1.0.13, so you naturally fall back to this code. I just realized that even the factory build of OpenSUSE is still on libusb-1.0.9. Current Ubuntu versions are on 1.0.12 at best. Didn't check others so far. Ouch. The 1.0.13 release is one year old by now. Fedora 19 is at 1.0.16 btw. So isn't this step a bit too early? There is always the 'git revert' option in case it turns out there are too many issues ... So what to do? Do you expect all the other distros to catch up regarding libusb until QEMU 1.7 is released? They will update once they figure this is needed for qemu 1.7 :) Updates will probably not yet be available at release time though. If we revert, thereby continue fallback to the old code, chances are high that nothing happens and we'll face the same issue for qemu 1.8. Given that there are some known issues in the host-linux code which are fixed in host-libusb I really want get rid of it. cheers, Gerd
Re: [Qemu-devel] [PATCH 1/7] usb: remove old usb-host code
On Mi, 2013-10-02 at 15:14 +0200, Jan Kiszka wrote: On 2013-09-19 11:34, Gerd Hoffmann wrote: The usb-host code has been rewritten for qemu 1.5 to use libusb, the old code has been left in as temporary fallback. Now we are two releases further out, targeting the 1.7 release. No major issues with the new code poped up until now. Time to remove it from tre tree. Should we ever need it again for some reason -- git has a copy for us in the history. Well, maybe not many users were actually exploiting the new libusb code, thus were able to produce feedback. Only very recent distros fulfill the need of = 1.0.13, so you naturally fall back to this code. I just realized that even the factory build of OpenSUSE is still on libusb-1.0.9. Current Ubuntu versions are on 1.0.12 at best. Didn't check others so far. Ouch. The 1.0.13 release is one year old by now. Fedora 19 is at 1.0.16 btw. So isn't this step a bit too early? There is always the 'git revert' option in case it turns out there are too many issues ... cheers, Gerd
Re: [Qemu-devel] [PATCH 1/7] usb: remove old usb-host code
On 2013-09-19 11:34, Gerd Hoffmann wrote: The usb-host code has been rewritten for qemu 1.5 to use libusb, the old code has been left in as temporary fallback. Now we are two releases further out, targeting the 1.7 release. No major issues with the new code poped up until now. Time to remove it from tre tree. Should we ever need it again for some reason -- git has a copy for us in the history. Well, maybe not many users were actually exploiting the new libusb code, thus were able to produce feedback. Only very recent distros fulfill the need of = 1.0.13, so you naturally fall back to this code. I just realized that even the factory build of OpenSUSE is still on libusb-1.0.9. Current Ubuntu versions are on 1.0.12 at best. Didn't check others so far. So isn't this step a bit too early? Jan -- Siemens AG, Corporate Technology, CT RTC ITP SES-DE Corporate Competence Center Embedded Linux
