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| author | Peter Xu <peterx@redhat.com> | 2025-06-13 10:07:53 -0400 |
|---|---|---|
| committer | Fabiano Rosas <farosas@suse.de> | 2025-07-11 10:37:35 -0300 |
| commit | 35290df01b064134a57339b2dbfee8713f9e6d85 (patch) | |
| tree | 07557081bf8041d3cd7e43166f27a58eb16eb7f5 | |
| parent | 2862d6d4fb09f57cabc4389fed34ae767ab2da94 (diff) | |
| download | qemu-35290df01b064134a57339b2dbfee8713f9e6d85.zip qemu-35290df01b064134a57339b2dbfee8713f9e6d85.tar.gz qemu-35290df01b064134a57339b2dbfee8713f9e6d85.tar.bz2 | |
migration/docs: Move docs for postcopy blocktime feature
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>
| -rw-r--r-- | docs/devel/migration/postcopy.rst | 36 |
1 files changed, 17 insertions, 19 deletions
diff --git a/docs/devel/migration/postcopy.rst b/docs/devel/migration/postcopy.rst index 82e7a84..e319388 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. |