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migration: postcopy_blocktime documentation

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Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Alexey Perevalov <a.perevalov@samsung.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-Id: <1521742647-25550-5-git-send-email-a.perevalov@samsung.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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Alexey Perevalov 2018-03-22 21:17:25 +03:00 committed by Dr. David Alan Gilbert
parent 575b0b332e
commit 9ed01779e8
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docs/devel/migration.rst
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@ -401,6 +401,20 @@ will now cause the transition from precopy to postcopy.
It can be issued immediately after migration is started or any
time later on. Issuing it after the end of a migration is harmless.
Blocktime is a postcopy live migration metric, intended to show how
long the vCPU was in state of interruptable sleep due to pagefault.
That metric is calculated both for all vCPUs as overlapped value, and
separately for each vCPU. These values are calculated on destination
side. To enable postcopy blocktime calculation, enter following
command on destination monitor:
``migrate_set_capability postcopy-blocktime on``
Postcopy blocktime can be retrieved by query-migrate qmp command.
postcopy-blocktime value of qmp command will show overlapped blocking
time for all vCPU, postcopy-vcpu-blocktime will show list of blocking
time per vCPU.
.. note::
During the postcopy phase, the bandwidth limits set using
``migrate_set_speed`` is ignored (to avoid delaying requested pages that