[PULL 03/26] migration/docs: Move docs for postcopy blocktime feature

Fabiano Rosas posted 26 patches 5 months, 1 week ago
Maintainers: Peter Xu <peterx@redhat.com>, Fabiano Rosas <farosas@suse.de>, Alex Williamson <alex.williamson@redhat.com>, "Cédric Le Goater" <clg@redhat.com>, Nicholas Piggin <npiggin@gmail.com>, Daniel Henrique Barboza <danielhb413@gmail.com>, Harsh Prateek Bora <harshpb@linux.ibm.com>, Halil Pasic <pasic@linux.ibm.com>, Christian Borntraeger <borntraeger@linux.ibm.com>, Jason Herne <jjherne@linux.ibm.com>, Richard Henderson <richard.henderson@linaro.org>, David Hildenbrand <david@redhat.com>, Ilya Leoshkevich <iii@linux.ibm.com>, Thomas Huth <thuth@redhat.com>, Eric Farman <farman@linux.ibm.com>, Matthew Rosato <mjrosato@linux.ibm.com>, Eric Blake <eblake@redhat.com>, Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>, John Snow <jsnow@redhat.com>, Markus Armbruster <armbru@redhat.com>, Laurent Vivier <lvivier@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>
[PULL 03/26] migration/docs: Move docs for postcopy blocktime feature
Posted by Fabiano Rosas 5 months, 1 week ago
From: Peter Xu <peterx@redhat.com>

Move it out of vanilla postcopy session, but instead a standalone feature.
When at it, removing the NOTE because it's incorrect now after introduction
of max-postcopy-bandwidth, which can control the throughput even for
postcopy phase.

Reviewed-by: Juraj Marcin <jmarcin@redhat.com>
Link: https://lore.kernel.org/r/20250613140801.474264-4-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
---
 docs/devel/migration/postcopy.rst | 36 +++++++++++++++----------------
 1 file changed, 17 insertions(+), 19 deletions(-)

diff --git a/docs/devel/migration/postcopy.rst b/docs/devel/migration/postcopy.rst
index 82e7a848c6..e319388d8f 100644
--- a/docs/devel/migration/postcopy.rst
+++ b/docs/devel/migration/postcopy.rst
@@ -33,25 +33,6 @@ 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 interruptible 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_parameter`` is ignored (to avoid delaying requested pages that
-  the destination is waiting for).
-
 Postcopy internals
 ==================
 
@@ -312,3 +293,20 @@ explicitly) to be sent in a separate preempt channel, rather than queued in
 the background migration channel.  Anyone who cares about latencies of page
 faults during a postcopy migration should enable this feature.  By default,
 it's not enabled.
+
+Postcopy blocktime statistics
+-----------------------------
+
+Blocktime is a postcopy live migration metric, intended to show how
+long the vCPU was in state of interruptible 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.
-- 
2.35.3