On Wed, Mar 25, 2020 at 10:14:30AM +0000, Daniel P. Berrangé wrote:
On Wed, Mar 25, 2020 at 10:01:02AM +0000, Richard W.M. Jones wrote:
On Wed, Mar 25, 2020 at 09:48:02AM +0000, Daniel P. Berrangé wrote:
On Wed, Mar 25, 2020 at 09:42:19AM +0000, Richard W.M. Jones wrote:
Now runs a complete set of tests, notably including the AIO test.
File descriptors are passed in and out as plain ints (instead of *os.File) for a couple of reasons: (1) We have to pass the plain int to syscall.Select. (2) Turning an fd into an os.File causes golang to set the blocking flag which is deeply unhelpful.
FWIW, using non-blocking FDs and syscall.Select is not normal best practice for Go, where the expected model would be to use goroutines with the file in blocking mode.
Right, however I couldn't find any documentation about how to integrate a C library with that mechanism. Does libvirt-go do anything like this?
What's the intended usage of the FD ? I was thinking it was just for doing plain read/write I/O from Go, but now I'm thinking this was wrong interpretation
http://libguestfs.org/libnbd.3.html#Socket-and-direction For example here's how it's integrated with glib: https://github.com/libguestfs/libnbd/blob/master/examples/glib-main-loop.c Integration with poll(2): https://github.com/libguestfs/libnbd/blob/a5fe64ab5323d649d348e61c9126ef7e72... It currently works from golang too, but it seems likely that synchronous calls like nbd_pread are blocking the golang main loop (because we make our own call to poll(2)). The asynch stuff also works (see libnbd_590_aio_copy_test.go in the attached patch) but it's rather awkward. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-builder quickly builds VMs from scratch http://libguestfs.org/virt-builder.1.html