[Qemu-devel] [PATCH v2 4/6] migration: postcopy_blocktime documentation

[Alexey Perevalov]

Reviewed-by: Dr. David Alan Gilbert <address@hidden>
Signed-off-by: Alexey Perevalov <address@hidden>
Reviewed-by: Juan Quintela <address@hidden>
Signed-off-by: Juan Quintela <address@hidden>
---
 docs/devel/migration.rst | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/docs/devel/migration.rst b/docs/devel/migration.rst
index e32b087..9342a8a 100644
--- a/docs/devel/migration.rst
+++ b/docs/devel/migration.rst
@@ -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
-- 
2.7.4