spschul
commented
5 years ago After discussion with @wes-b here's a few considerations.
There is a maximum on memory allowed for the libusb pool, specified with the environment variable K4A_MAX_LIBUSB_POOL. For Windows, K4A_MAX_LIBUSB_POOL=80000000 but for Linux, K4A_MAX_LIBUSB_POOL=1000000. This limit was chosen for Windows to have enough memory to not drop frames, but on Linux it needed to be smaller because of the default size of usbfs_memory_mb. After finding this fix, it's clear that we can support doing larger libusb_pool sizes.
If anyone has issues with dropping frames, this could potentially be a solution.
Currently, we know that 16MB of memory for usbfs_memory_mb is sufficient with 1 camera on Linux with K4A_MAX_LIBUSB_POOL=1000000. So, we can conclude that as an upper bound 16MB * (number of cameras) allocated for usbfs_memory_mb should be sufficient.
However, if you go ahead and set K4A_MAX_LIBUSB_POOL=8000000, which will probably help with not dropping frames, you should instead set usbfs_memory_mb to 16MB 8 (number of cameras) = 128MB * (number of cameras).
Note that these are upper bounds; they are probably overkill. It would be nice to find a more precise specification.
We should also add checks to the project on relevant calls to libusb and libuvc to check for these considerations.
somacoder
ruoyuwangeel4930
However, I still cannot use two devices at the same time. Here is the error message:
My system is Ubuntu18.04 and I used apt-get to install the SDK.
Both devices are good when I test them separately. Do you have any idea about the possible cause to this problem? Thanks!
After I set K4A_LOG_LEVEL=i, I saw this information in the terminal:
pfagomez
wes-b
ichlubna
Describe the bug When streaming with multiple devices on Linux, when the program calls
start_camerasthe program will fail with errors such as an error forlibusb_submit_transferand similar-looking errors. Diving deeper, it becomes clear that a function withinlibusbis failing, returningENOMEMindicating that the kernel is out of memory. The problem is that there's a setting (readable at/sys/module/usbcore/parameters/usbfs_memory_mb) that limits the amount of memory available for USB IO. However, some applications that require more intensive usage of that memory often use more than that. As documented at https://github.com/OpenKinect/libfreenect2/issues/97, there is a fix for this: allocate more memory. I tried it with 32mb instead of 16 and it seems to be working (I ran into issues the first time I tested it but they seemed unrelated; documenting in case someone else runs into this).@wes-b I'd like to discuss how to handle this; right now I'm leaning towards having a section on it in the docs soon and somewhere early, perhaps even recommending that users preemptively add more memory. Do we want to attempt to make this fix a part of the package? I think that is too much, and also we don't know how much memory people will have to spare, but also don't know how much memory they'll need. Using many cameras will require more memory, etc.
To fix on AMD64, using 32 mb instead of 16,
/etc/default/grub, replacing the line that saysGRUB_CMDLINE_LINUX_DEFAULT="quiet splash"withGRUB_CMDLINE_LINUX_DEFAULT="quiet splash usbcore.usbfs_memory_mb=32"sudo update-grubTo fix on ARM64 (Jetson Nano)
/boot/extlinux/extlinux.confAPPEND ${cbootargs} quiettoAPPEND ${cbootargs} usbcore.usbfs_memory_mb=128 usbcore.autosuspend=-1. (It is probably fine to leave quiet and remove usbcore.autosuspend=-1 but that was not tested.)cat /sys/module/usbcore/parameters/usbfs_memory_mbTo Reproduce Stream from 2 devices on Linux
Expected behavior Programs do not crash in this case
Desktop (please complete the following information):