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David Alan Gilbert" , Fabiano Rosas Subject: [PATCH v2 03/11] migration/docs: Move docs for postcopy blocktime feature Date: Mon, 9 Jun 2025 12:18:47 -0400 Message-ID: <20250609161855.6603-4-peterx@redhat.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250609161855.6603-1-peterx@redhat.com> References: <20250609161855.6603-1-peterx@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org 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 Signed-off-by: Peter Xu --- 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. -- 2.49.0