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David Alan Gilbert" , Juraj Marcin , Prasad Pandit , Daniel P . =?utf-8?Q?Berrang=C3=A9?= , Julia Suvorova , Fabiano Rosas Subject: Re: [PATCH] migration: Deprecate query-migrationthreads command In-Reply-To: <20241021215220.982325-1-peterx@redhat.com> (Peter Xu's message of "Mon, 21 Oct 2024 17:52:20 -0400") References: <20241021215220.982325-1-peterx@redhat.com> Date: Tue, 22 Oct 2024 10:41:29 +0200 Message-ID: <87froo34xy.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.421, 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_H2=-1.699, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_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 Peter Xu writes: > Per previous discussion [1,2], this patch deprecates query-migrationthreads > command. > > To summarize, the major reason of the deprecation is due to no sensible way > to consume the API properly: > > (1) The reported list of threads are incomplete (ignoring destination > threads and non-multifd threads). > > (2) For CPU pinning, there's no way to properly pin the threads with > the API if the threads will start running right away after migration > threads can be queried, so the threads will always run on the default > cores for a short window. > > (3) For VM debugging, one can use "-name $VM,debug-threads=on" instead, > which will provide proper names for all migration threads. > > [1] https://lore.kernel.org/r/20240930195837.825728-1-peterx@redhat.com > [2] https://lore.kernel.org/r/20241011153417.516715-1-peterx@redhat.com > > Signed-off-by: Peter Xu > --- > docs/about/deprecated.rst | 8 ++++++++ > qapi/migration.json | 6 +++++- > migration/threadinfo.c | 4 ++++ > 3 files changed, 17 insertions(+), 1 deletion(-) > > diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst > index ce38a3d0cf..ffb147e896 100644 > --- a/docs/about/deprecated.rst > +++ b/docs/about/deprecated.rst > @@ -147,6 +147,14 @@ options are removed in favor of using explicit ``blockdev-create`` and > ``blockdev-add`` calls. See :doc:`/interop/live-block-operations` for > details. > > +``query-migrationthreads`` (since 9.2) > +''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' > + > +To be removed with no replacement, as it reports only a limited set of > +threads (for example, it only reports source side of multifd threads, > +without reporting any destination threads, or non-multifd source threads). > +For debugging purpose, please use ``-name $VM,debug-threads=on`` instead. This covers commit message items (1) and (3), but not (2). Observation, not objection. > + > Incorrectly typed ``device_add`` arguments (since 6.2) > '''''''''''''''''''''''''''''''''''''''''''''''''''''' > > diff --git a/qapi/migration.json b/qapi/migration.json > index 3af6aa1740..a71a9f0cd3 100644 > --- a/qapi/migration.json > +++ b/qapi/migration.json > @@ -2284,12 +2284,16 @@ > # > # Returns information of migration threads > # > +# Features: Blank line, please. > +# @deprecated: This command is deprecated with no replacement yet. > +# > # Returns: @MigrationThreadInfo > # > # Since: 7.2 > ## > { 'command': 'query-migrationthreads', > - 'returns': ['MigrationThreadInfo'] } > + 'returns': ['MigrationThreadInfo'], > + 'features': ['deprecated'] } > > ## > # @snapshot-save: > diff --git a/migration/threadinfo.c b/migration/threadinfo.c > index 262990dd75..2867413420 100644 > --- a/migration/threadinfo.c > +++ b/migration/threadinfo.c > @@ -13,6 +13,7 @@ > #include "qemu/osdep.h" > #include "qemu/queue.h" > #include "qemu/lockable.h" > +#include "qemu/error-report.h" > #include "threadinfo.h" > > QemuMutex migration_threads_lock; > @@ -52,6 +53,9 @@ MigrationThreadInfoList *qmp_query_migrationthreads(Error **errp) > MigrationThread *thread = NULL; > > QEMU_LOCK_GUARD(&migration_threads_lock); > + > + warn_report("Command 'query-migrationthreads' is deprecated"); We don't normally do this for QMP commands. Management applications can use -compat deprecated-input=reject to check they're not sending deprecated commands or arguments. Suggest to drop. > + > QLIST_FOREACH(thread, &migration_threads, node) { > MigrationThreadInfo *info = g_new0(MigrationThreadInfo, 1); > info->name = g_strdup(thread->name); Acked-by: Markus Armbruster