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Wed, 21 Feb 2024 12:56:38 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id ha5cOQbz1WV+awAAD6G6ig (envelope-from ); Wed, 21 Feb 2024 12:56:38 +0000 From: Fabiano Rosas To: Peter Xu Cc: qemu-devel@nongnu.org Subject: Re: [PATCH] migration: Fix qmp_query_migrate mbps value In-Reply-To: References: <20240219194457.26923-1-farosas@suse.de> Date: Wed, 21 Feb 2024 09:56:36 -0300 Message-ID: <87y1beascb.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain Authentication-Results: smtp-out1.suse.de; dkim=pass header.d=suse.de header.s=susede2_rsa header.b=JigMZKdH; dkim=pass header.d=suse.de header.s=susede2_ed25519 header.b=7RQM1nZx X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spamd-Result: default: False [-4.51 / 50.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; BAYES_HAM(-3.00)[100.00%]; MIME_GOOD(-0.10)[text/plain]; NEURAL_HAM_LONG(-1.00)[-1.000]; RCVD_COUNT_THREE(0.00)[3]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.de:+]; RCPT_COUNT_TWO(0.00)[2]; MX_GOOD(-0.01)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:dkim,suse.de:email]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; NEURAL_HAM_SHORT(-0.20)[-1.000]; RCVD_TLS_ALL(0.00)[]; MID_RHS_MATCH_FROM(0.00)[] X-Rspamd-Queue-Id: A66CC21E91 Received-SPF: pass client-ip=195.135.223.130; envelope-from=farosas@suse.de; helo=smtp-out1.suse.de X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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 Peter Xu writes: > On Mon, Feb 19, 2024 at 04:44:57PM -0300, Fabiano Rosas wrote: >> The QMP command query_migrate might see incorrect throughput numbers >> if it runs after we've set the migration completion status but before >> migration_calculate_complete() has updated s->total_time and s->mbps. >> >> The migration status would show COMPLETED, but the throughput value >> would be the one from the last iteration and not the one from the >> whole migration. This will usually be a larger value due to the time >> period being smaller (one iteration). >> >> Move migration_calculate_complete() earlier so that the status >> MIGRATION_STATUS_COMPLETED is only emitted after the final counters >> update. >> >> Signed-off-by: Fabiano Rosas >> --- >> CI run: https://gitlab.com/farosas/qemu/-/pipelines/1182405776 >> --- >> migration/migration.c | 10 ++++++---- >> 1 file changed, 6 insertions(+), 4 deletions(-) >> >> diff --git a/migration/migration.c b/migration/migration.c >> index ab21de2cad..7486d59da0 100644 >> --- a/migration/migration.c >> +++ b/migration/migration.c >> @@ -102,6 +102,7 @@ static int migration_maybe_pause(MigrationState *s, >> int new_state); >> static void migrate_fd_cancel(MigrationState *s); >> static bool close_return_path_on_source(MigrationState *s); >> +static void migration_calculate_complete(MigrationState *s); >> >> static void migration_downtime_start(MigrationState *s) >> { >> @@ -2746,6 +2747,7 @@ static void migration_completion(MigrationState *s) >> migrate_set_state(&s->state, MIGRATION_STATUS_ACTIVE, >> MIGRATION_STATUS_COLO); >> } else { >> + migration_calculate_complete(s); >> migrate_set_state(&s->state, current_active_state, >> MIGRATION_STATUS_COMPLETED); >> } >> @@ -2784,6 +2786,7 @@ static void bg_migration_completion(MigrationState *s) >> goto fail; >> } >> >> + migration_calculate_complete(s); >> migrate_set_state(&s->state, current_active_state, >> MIGRATION_STATUS_COMPLETED); >> return; >> @@ -2993,12 +2996,15 @@ static void migration_calculate_complete(MigrationState *s) >> int64_t end_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME); >> int64_t transfer_time; >> >> + /* QMP could read from these concurrently */ >> + bql_lock(); >> migration_downtime_end(s); >> s->total_time = end_time - s->start_time; >> transfer_time = s->total_time - s->setup_time; >> if (transfer_time) { >> s->mbps = ((double) bytes * 8.0) / transfer_time / 1000; >> } >> + bql_unlock(); > > The lock is not needed? > > AFAIU that was needed because of things like runstate_set() rather than > setting of these fields. > Don't we need to keep the total_time and mbps update atomic? Otherwise query-migrate might see (say) total_time=0 and mbps= or total_time= and mbps=. Also, what orders s->mbps update before the s->state update? I'd say we should probably hold the lock around the whole total_time,mbps,state update. I'm not entirely sure, what do you think? > See migration_update_counters() where it also updates mbps without holding > a lock. Here it might be less important since it's the middle of the migration, there will proabably be more than one query-migrate which would see the correct values. > > Other than that it looks all good. > >> } >> >> static void update_iteration_initial_status(MigrationState *s) >> @@ -3145,7 +3151,6 @@ static void migration_iteration_finish(MigrationState *s) >> bql_lock(); >> switch (s->state) { >> case MIGRATION_STATUS_COMPLETED: >> - migration_calculate_complete(s); >> runstate_set(RUN_STATE_POSTMIGRATE); >> break; >> case MIGRATION_STATUS_COLO: >> @@ -3189,9 +3194,6 @@ static void bg_migration_iteration_finish(MigrationState *s) >> bql_lock(); >> switch (s->state) { >> case MIGRATION_STATUS_COMPLETED: >> - migration_calculate_complete(s); >> - break; >> - >> case MIGRATION_STATUS_ACTIVE: >> case MIGRATION_STATUS_FAILED: >> case MIGRATION_STATUS_CANCELLED: >> -- >> 2.35.3 >>