afda589d05
When calling virNodeDeviceDefineXML() to define a new mediated device, we call virMdevctlDefine() and then wait for the new device to appear in the driver's device list before returning. This caused long delays due to the behavior of nodeDeviceFindNewMediatedDevice(). This function checks to see if the device is in the list and then waits for 5s before checking again. Because mdevctl is relatively slow to query the list of defined devices[0], the newly-defined device was generally not in the device list when we first checked. This results in libvirt almost always taking at least 5s to complete this API call for mediated devices, which is unacceptable. In order to avoid this long delay, we resort to a workaround. If the call to virMdevctlDefine() was successful, we can assume that this new device will exist the next time we query mdevctl for new devices. So we simply add this provisional device definition directly to the nodedev driver's device list and return from the function. At some point in the future, the mdevctl handler will run and the "official" device will be processed, which will update the provisional device if any new details need to be added. The reason that this is not necessary for virNodeDeviceCreateXML() is because detecting newly-created (not defined) mdevs happens through udev instead of mdevctl. And nodeDeviceFindNewMediatedDevice() always calls 'udevadm settle' before checking to see whether the device is in the list. This allows us to wait just long enough for all udev events to be processed, so the device is almost always in the list the first time we check and so we almost never end up hitting the 5s sleep. [0] on my machine, 'mdevctl list --defined' took around 0.8s to complete for only 3 defined mdevs. Signed-off-by: Jonathon Jongsma <jjongsma@redhat.com> Reviewed-by: Erik Skultety <eskultet@redhat.com> |
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| CONTRIBUTING.rst | ||
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Libvirt API for virtualization
Libvirt provides a portable, long term stable C API for managing the virtualization technologies provided by many operating systems. It includes support for QEMU, KVM, Xen, LXC, bhyve, Virtuozzo, VMware vCenter and ESX, VMware Desktop, Hyper-V, VirtualBox and the POWER Hypervisor.
For some of these hypervisors, it provides a stateful management daemon which runs on the virtualization host allowing access to the API both by non-privileged local users and remote users.
Layered packages provide bindings of the libvirt C API into other languages including Python, Perl, PHP, Go, Java, OCaml, as well as mappings into object systems such as GObject, CIM and SNMP.
Further information about the libvirt project can be found on the website:
License
The libvirt C API is distributed under the terms of GNU Lesser General Public License, version 2.1 (or later). Some parts of the code that are not part of the C library may have the more restrictive GNU General Public License, version 2.0 (or later). See the files COPYING.LESSER and COPYING for full license terms & conditions.
Installation
Instructions on building and installing libvirt can be found on the website:
https://libvirt.org/compiling.html
Contributing
The libvirt project welcomes contributions in many ways. For most components the best way to contribute is to send patches to the primary development mailing list. Further guidance on this can be found on the website:
https://libvirt.org/contribute.html
Contact
The libvirt project has two primary mailing lists:
- libvirt-users@redhat.com (for user discussions)
- libvir-list@redhat.com (for development only)
Further details on contacting the project are available on the website: