{"id":2221042,"url":"http://patchwork.ozlabs.org/api/1.0/patches/2221042/?format=json","project":{"id":14,"url":"http://patchwork.ozlabs.org/api/1.0/projects/14/?format=json","name":"QEMU Development","link_name":"qemu-devel","list_id":"qemu-devel.nongnu.org","list_email":"qemu-devel@nongnu.org","web_url":"","scm_url":"","webscm_url":""},"msgid":"<20260408165559.157108-12-peterx@redhat.com>","date":"2026-04-08T16:55:55","name":"[11/14] migration: Calculate expected downtime on demand","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"e25c974a47da0c412cf401d593616b5e94eef7b9","submitter":{"id":67717,"url":"http://patchwork.ozlabs.org/api/1.0/people/67717/?format=json","name":"Peter Xu","email":"peterx@redhat.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/qemu-devel/patch/20260408165559.157108-12-peterx@redhat.com/mbox/","series":[{"id":499176,"url":"http://patchwork.ozlabs.org/api/1.0/series/499176/?format=json","date":"2026-04-08T16:55:55","name":"migration/vfio: Fix a few issues on API misuse or statistic reports","version":1,"mbox":"http://patchwork.ozlabs.org/series/499176/mbox/"}],"check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2221042/checks/","tags":{},"headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=mimecast20190719 header.b=U90wPZhb;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=google header.b=IAqHhfWb;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; 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Szmigiero\" , =?utf-8?q?Daniel_P_?=\n\t=?utf-8?q?=2E_Berrang=C3=A9?= ,\n Zhiyi Guo , Juraj Marcin ,\n Peter Xu , Prasad Pandit ,\n Avihai Horon , Kirti Wankhede ,\n\t=?utf-8?q?C=C3=A9dric_Le_Goater?= ,\n Fabiano Rosas , Joao Martins ,\n Markus Armbruster , Alex Williamson ","Subject":"[PATCH 11/14] migration: Calculate expected downtime on demand","Date":"Wed, 8 Apr 2026 12:55:55 -0400","Message-ID":"<20260408165559.157108-12-peterx@redhat.com>","X-Mailer":"git-send-email 2.53.0","In-Reply-To":"<20260408165559.157108-1-peterx@redhat.com>","References":"<20260408165559.157108-1-peterx@redhat.com>","MIME-Version":"1.0","Content-Transfer-Encoding":"8bit","Received-SPF":"pass client-ip=170.10.129.124; envelope-from=peterx@redhat.com;\n helo=us-smtp-delivery-124.mimecast.com","X-Spam_score_int":"-25","X-Spam_score":"-2.6","X-Spam_bar":"--","X-Spam_report":"(-2.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.54,\n DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1,\n RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001,\n RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001,\n SPF_HELO_PASS=-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":"qemu development ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org"},"content":"This value does not need to be calculated as frequent. Only calculate it\non demand when query-migrate happened. With that we can remove the\nvariable in MigrationState.\n\nThis paves way for fixing this value to include all modules (not only RAM\nbut others too).\n\nSigned-off-by: Peter Xu \n---\n migration/migration.h | 2 +-\n migration/migration.c | 25 ++++++++++++-------------\n 2 files changed, 13 insertions(+), 14 deletions(-)","diff":"diff --git a/migration/migration.h b/migration/migration.h\nindex e504df6915..32543800b6 100644\n--- a/migration/migration.h\n+++ b/migration/migration.h\n@@ -359,7 +359,6 @@ struct MigrationState {\n /* Timestamp when VM is down (ms) to migrate the last stuff */\n int64_t downtime_start;\n int64_t downtime;\n- int64_t expected_downtime;\n bool capabilities[MIGRATION_CAPABILITY__MAX];\n int64_t setup_time;\n \n@@ -594,6 +593,7 @@ void migration_cancel(void);\n void migration_populate_vfio_info(MigrationInfo *info);\n void migration_reset_vfio_bytes_transferred(void);\n void postcopy_temp_page_reset(PostcopyTmpPage *tmp_page);\n+int64_t migration_downtime_calc_expected(MigrationState *s);\n \n /*\n * Migration thread waiting for return path thread. Return non-zero if an\ndiff --git a/migration/migration.c b/migration/migration.c\nindex a1a02e3a9f..f12cd9efd3 100644\n--- a/migration/migration.c\n+++ b/migration/migration.c\n@@ -1041,6 +1041,17 @@ static bool migrate_show_downtime(MigrationState *s)\n return (s->state == MIGRATION_STATUS_COMPLETED) || migration_in_postcopy();\n }\n \n+/* Return expected downtime (unit: milliseconds) */\n+int64_t migration_downtime_calc_expected(MigrationState *s)\n+{\n+ if (mig_stats.dirty_sync_count <= 1) {\n+ return migrate_downtime_limit();\n+ }\n+\n+ return mig_stats.dirty_bytes_last_sync /\n+ migration_get_switchover_bw(s) * 1000;\n+}\n+\n static void populate_time_info(MigrationInfo *info, MigrationState *s)\n {\n info->has_status = true;\n@@ -1061,7 +1072,7 @@ static void populate_time_info(MigrationInfo *info, MigrationState *s)\n info->downtime = s->downtime;\n } else {\n info->has_expected_downtime = true;\n- info->expected_downtime = s->expected_downtime;\n+ info->expected_downtime = migration_downtime_calc_expected(s);\n }\n }\n \n@@ -1649,7 +1660,6 @@ int migrate_init(MigrationState *s, Error **errp)\n s->mbps = 0.0;\n s->pages_per_second = 0.0;\n s->downtime = 0;\n- s->expected_downtime = 0;\n s->setup_time = 0;\n s->start_postcopy = false;\n s->migration_thread_running = false;\n@@ -3162,15 +3172,6 @@ static void migration_update_counters(MigrationState *s,\n s->pages_per_second = (double) transferred_pages /\n (((double) time_spent / 1000.0));\n \n- /*\n- * if we haven't sent anything, we don't want to\n- * recalculate. 10000 is a small enough number for our purposes\n- */\n- if (mig_stats.dirty_pages_rate && transferred > 10000) {\n- s->expected_downtime =\n- mig_stats.dirty_bytes_last_sync / switchover_bw_per_ms;\n- }\n-\n migration_rate_reset();\n \n update_iteration_initial_status(s);\n@@ -3816,8 +3817,6 @@ void migration_start_outgoing(MigrationState *s)\n bool resume = (s->state == MIGRATION_STATUS_POSTCOPY_RECOVER_SETUP);\n int ret;\n \n- s->expected_downtime = migrate_downtime_limit();\n-\n if (resume) {\n /* This is a resumed migration */\n rate_limit = migrate_max_postcopy_bandwidth();\n","prefixes":["11/14"]}