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GET /api/1.0/patches/2221156/?format=api
{ "id": 2221156, "url": "http://patchwork.ozlabs.org/api/1.0/patches/2221156/?format=api", "project": { "id": 14, "url": "http://patchwork.ozlabs.org/api/1.0/projects/14/?format=api", "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": "<20260408165559.157108-11-peterx@redhat.com>", "date": "2026-04-08T16:55:54", "name": "[10/14] migration: Introduce a helper to return switchover bw estimate", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "40910d22baa7354680a125e81bcdbdcb5281a2b6", "submitter": { "id": 67717, "url": "http://patchwork.ozlabs.org/api/1.0/people/67717/?format=api", "name": "Peter Xu", "email": "peterx@redhat.com" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/qemu-devel/patch/20260408165559.157108-11-peterx@redhat.com/mbox/", "series": [ { "id": 499176, "url": "http://patchwork.ozlabs.org/api/1.0/series/499176/?format=api", "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/2221156/checks/", "tags": {}, "headers": { "Return-Path": "<qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org>", "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=F8EGtmB8;\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=NG+0FBbj;\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\" <mail@maciej.szmigiero.name>, =?utf-8?q?Daniel_P_?=\n\t=?utf-8?q?=2E_Berrang=C3=A9?= <berrange@redhat.com>,\n Zhiyi Guo <zhguo@redhat.com>, Juraj Marcin <jmarcin@redhat.com>,\n Peter Xu <peterx@redhat.com>, Prasad Pandit <ppandit@redhat.com>,\n Avihai Horon <avihaih@nvidia.com>, Kirti Wankhede <kwankhede@nvidia.com>,\n\t=?utf-8?q?C=C3=A9dric_Le_Goater?= <clg@redhat.com>,\n Fabiano Rosas <farosas@suse.de>, Joao Martins <joao.m.martins@oracle.com>,\n Markus Armbruster <armbru@redhat.com>, Alex Williamson <alex@shazbot.org>", "Subject": "[PATCH 10/14] migration: Introduce a helper to return switchover bw\n estimate", "Date": "Wed, 8 Apr 2026 12:55:54 -0400", "Message-ID": "<20260408165559.157108-11-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 <qemu-devel.nongnu.org>", "List-Unsubscribe": "<https://lists.nongnu.org/mailman/options/qemu-devel>,\n <mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>", "List-Archive": "<https://lists.nongnu.org/archive/html/qemu-devel>", "List-Post": "<mailto:qemu-devel@nongnu.org>", "List-Help": "<mailto:qemu-devel-request@nongnu.org?subject=help>", "List-Subscribe": "<https://lists.nongnu.org/mailman/listinfo/qemu-devel>,\n <mailto:qemu-devel-request@nongnu.org?subject=subscribe>", "Errors-To": "qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org", "Sender": "qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org" }, "content": "Add a helper migration_get_switchover_bw() to return an estimate of\nswitchover bandwidth. Use it to simplify the current code.\n\nThis will be used in later to remove expected_downtime.\n\nWhen at it, remove two qatomic_read() to shrink the lines because atomic\nops are not needed when it's always the same thread who does the updates.\n\nReviewed-by: Juraj Marcin <jmarcin@redhat.com>\nSigned-off-by: Peter Xu <peterx@redhat.com>\n---\n migration/migration.c | 48 +++++++++++++++++++++----------------------\n 1 file changed, 24 insertions(+), 24 deletions(-)", "diff": "diff --git a/migration/migration.c b/migration/migration.c\nindex 57d91ad9e3..a1a02e3a9f 100644\n--- a/migration/migration.c\n+++ b/migration/migration.c\n@@ -984,6 +984,21 @@ void migrate_send_rp_resume_ack(MigrationIncomingState *mis, uint32_t value)\n migrate_send_rp_message(mis, MIG_RP_MSG_RESUME_ACK, sizeof(buf), &buf);\n }\n \n+/*\n+ * Returns the estimated switchover bandwidth (unit: bytes / seconds)\n+ */\n+static double migration_get_switchover_bw(MigrationState *s)\n+{\n+ uint64_t switchover_bw = migrate_avail_switchover_bandwidth();\n+\n+ if (switchover_bw) {\n+ /* If user specified, prioritize this value and don't estimate */\n+ return (double)switchover_bw;\n+ }\n+\n+ return s->mbps / 8 * 1000 * 1000;\n+}\n+\n bool migration_is_running(void)\n {\n MigrationState *s = current_migration;\n@@ -3126,37 +3141,22 @@ static void migration_update_counters(MigrationState *s,\n {\n uint64_t transferred, transferred_pages, time_spent;\n uint64_t current_bytes; /* bytes transferred since the beginning */\n- uint64_t switchover_bw;\n- /* Expected bandwidth when switching over to destination QEMU */\n- double expected_bw_per_ms;\n- double bandwidth;\n+ double switchover_bw_per_ms;\n \n if (current_time < s->iteration_start_time + BUFFER_DELAY) {\n return;\n }\n \n- switchover_bw = migrate_avail_switchover_bandwidth();\n current_bytes = migration_transferred_bytes();\n transferred = current_bytes - s->iteration_initial_bytes;\n time_spent = current_time - s->iteration_start_time;\n- bandwidth = (double)transferred / time_spent;\n-\n- if (switchover_bw) {\n- /*\n- * If the user specified a switchover bandwidth, let's trust the\n- * user so that can be more accurate than what we estimated.\n- */\n- expected_bw_per_ms = (double)switchover_bw / 1000;\n- } else {\n- /* If the user doesn't specify bandwidth, we use the estimated */\n- expected_bw_per_ms = bandwidth;\n- }\n-\n- s->threshold_size = expected_bw_per_ms * migrate_downtime_limit();\n-\n s->mbps = (((double) transferred * 8.0) /\n ((double) time_spent / 1000.0)) / 1000.0 / 1000.0;\n \n+ /* NOTE: only update this after bandwidth (s->mbps) updated */\n+ switchover_bw_per_ms = migration_get_switchover_bw(s) / 1000;\n+ s->threshold_size = switchover_bw_per_ms * migrate_downtime_limit();\n+\n transferred_pages = ram_get_total_transferred_pages() -\n s->iteration_initial_pages;\n s->pages_per_second = (double) transferred_pages /\n@@ -3166,10 +3166,9 @@ static void migration_update_counters(MigrationState *s,\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 (qatomic_read(&mig_stats.dirty_pages_rate) &&\n- transferred > 10000) {\n+ if (mig_stats.dirty_pages_rate && transferred > 10000) {\n s->expected_downtime =\n- qatomic_read(&mig_stats.dirty_bytes_last_sync) / expected_bw_per_ms;\n+ mig_stats.dirty_bytes_last_sync / switchover_bw_per_ms;\n }\n \n migration_rate_reset();\n@@ -3178,7 +3177,8 @@ static void migration_update_counters(MigrationState *s,\n \n trace_migrate_transferred(transferred, time_spent,\n /* Both in unit bytes/ms */\n- bandwidth, switchover_bw / 1000,\n+ (uint64_t)s->mbps,\n+ (uint64_t)switchover_bw_per_ms,\n s->threshold_size);\n }\n \n", "prefixes": [ "10/14" ] }