On 12/23/2010 05:49 AM, Paolo Bonzini wrote:
On 12/22/2010 11:27 PM, Eric Blake wrote:
https://bugzilla.redhat.com/show_bug.cgi?id=620363
When using -incoming stdio or -incoming exec:cat, qemu keeps the stdin fd open long after the migration is complete. Not to mention that exec:cat is horribly inefficient, by doubling the I/O and going through a popen interface in qemu.
The new -incoming fd: of qemu 0.12.0 closes the fd after using it, and allows us to bypass an intermediary cat process for less I/O.
It would also be possible to fix this bug for qemu< 0.12.0, by creating a dummy 'cat' process that reads from real fd and writes to a pipe, and pass the other end of the pipe into -incoming exec:cat or -incoming stdio, at the expense of even more I/O. I don't know if that is worth the patch, though.
Since you are at it, you may also want to replace the usage of netcat and Unix sockets with "-incoming fd:" and a one-way pipe.
Not sure it's worth it. Is unix:path any less efficient than creating a one-way pipe for use by fd:n? Also, we can't replace netcat; the use of '-incoming "exec:nc -lU path"' is only used in libvirt that predates '-incoming unix:path', which also happens to predate '-incoming fd:n'. -- Eric Blake eblake@redhat.com +1-801-349-2682 Libvirt virtualization library http://libvirt.org