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This reverts commit ef1065cf5ac; see also this bug report: https://bugzilla.redhat.com/show_bug.cgi?id=751900 In qemu 0.15.1 and earlier, during migration to file, the qemu_savevm_state_begin and qemu_savevm_state_iterate methods will both process as much migration data as possible until either 1. The file descriptor returns EAGAIN 2. The bandwidth rate limit is reached If we set the rate limit to ULONG_MAX, test 2 never becomes true. We're passing a plain file descriptor to QEMU and POSIX does not support EAGAIN on regular files / block devices, so test 1 never becomes true either. In the 'virsh save --bypass-cache' case, we pass a pipe instead of a regular fd, but using a pipe adds I/O overhead, so always passing a pipe just so qemu can see EAGAIN doesn't seem nice. The ultimate fix needs to come from qemu - background migration must respect asynchronous abort requests, or else periodically return control to the main handling loop without an EAGAIN and without waiting to hit an insanely large amount of data. But until a version of qemu is fixed to support "unlimited" data rates while still allowing cancellation, the best we can do is avoid the automatic use of unlimited rates from within libvirt (users can still explicitly change the migration rates, if they are aware that they are giving up the ability to cancel a job). Reverting the lone use of QEMU_DOMAIN_FILE_MIG_BANDWIDTH_MAX is the simplest patch; this slows migration back down to a default 32M/sec cap, but also ensures that the main qemu processing loop will still be responsive to cancellation requests. Hopefully upstream qemu will provide us a means of safely using unlimited speed, including a runtime probe of that capability. * src/qemu/qemu_migration.c (qemuMigrationToFile): Revert attempt to use unlimited migration bandwidth when migrating to file. Signed-off-by: Daniel Veillard <veillard@redhat.com> Signed-off-by: Eric Blake <eblake@redhat.com>
LibVirt : simple API for virtualization
Libvirt is a C toolkit to interact with the virtualization capabilities
of recent versions of Linux (and other OSes). It is free software
available under the GNU Lesser General Public License. Virtualization of
the Linux Operating System means the ability to run multiple instances of
Operating Systems concurrently on a single hardware system where the basic
resources are driven by a Linux instance. The library aim at providing
long term stable C API initially for the Xen paravirtualization but
should be able to integrate other virtualization mechanisms if needed.
Daniel Veillard <veillard@redhat.com>