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Tsirkin'" , Stefan Hajnoczi , Paolo Bonzini , =?UTF-8?q?=27Daniel=20P=20=2E=20Berrang=C3=A9=27?= , Jason Wang Cc: Zhang Chen Subject: [PATCH V14 00/15] iothread: Support tracking and querying IOThread holder Date: Tue, 1 Sep 2026 00:00:21 +0800 Message-ID: <20260831160038.221776-1-zhangckid@gmail.com> X-Mailer: git-send-email 2.55.0 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2607:f8b0:4864:20::1030; envelope-from=zhangckid@gmail.com; helo=mail-pj1-x1030.google.com X-Spam_score_int: 12 X-Spam_score: 1.2 X-Spam_bar: + X-Spam_report: (1.2 / 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, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no 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: , 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 ### Motivation Currently, the relationship between IOThreads and the resources using them is opaque. From a management perspective, it is difficult to determine which devices or block exports are currently associated with a specific IOThread via QMP or HMP. This series introduces a "holder" tracking mechanism based on QOM paths or block exports to significantly improve IOThread observability. In high-performance virtualization environments, users often pre-allocate a set of IOThreads to serve as a persistent thread pool. During device hotplug/unplug cycles, while IOThread objects remain persistent, their attachment state changes dynamically. By tracking these "holders," administrators can use `query-iothreads` to monitor the real-time load distribution of the thread pool and identify which specific devices (e.g., virtio-blk, BlockExport) are attached to which thread. ### Technical Overview * Holder tracking Add a QAPI holder list to each IOThread. A holder identifies either a QOM object by its canonical path or a block export by its unique BlockExportOptions ID. * Explicit reference lifecycle Add iothread_ref_and_get_aio_context() and the matching iothread_unref_and_put_aio_context(). Acquiring an AioContext registers a holder and keeps the IOThread alive until the matching put. Legacy callers without a matching lifecycle use the explicitly named iothread_unsafe_get_aio_context(). The ambiguous legacy iothread_get_aio_context() is removed after all production callers are migrated. * Subsystem integration Track holders for block exports, monitors, virtio-blk, virtio-scsi, virtio queue mappings, virtio balloon thread pinning, COLO compare, vfio-user proxy, and xen-block. * Introspection Extend IOThreadInfo with a holders array returned by query-iothreads. Display the same information with info iothreads. ### V14 -> V13 Changelog - Renamed patch 3 and clarified that it introduces holder-tracking infrastructure, with users converted in subsequent patches. - Documented that monitor holders are not visible to management applications, while retaining the tracking for a consistent holder and IOThread reference lifecycle. - Rebased on the latest upstream. ### V13 -> V12 Changelog - Refactored block export IOThread reference handling with shared init/cleanup helpers and preserved the existing single-IOThread driver arguments. - Moved monitor IOThread cleanup to the QOM unparent callback, where the canonical path is still available. - Kept internal IOThreads hidden from query-iothreads. - Made virtio queue-mapping holder arguments const. - Improved some detail comments. ### V12 -> V11 Changelog - Change the function name from the "iothread_put_aio_context()" to "iothread_unref_and_put_aio_context()" match the "iothread_unref_and_put_aio_context". - Fix unnecessary char * cast since the holder variable is declared const. - Add detailed commit msg in patch 06/15. - Optimize the HMP print in patch 13/15. - Rebase code on upstream. ### V11 -> V10 Changelog - Keep iothread_ref_and_get_aio_context() as an explicit acquiring API instead of merging it into iothread_get_aio_context(). - Retain iothread_get_aio_context() during the caller migration so every intermediate patch builds, then remove it in patch 14. - Update patch 15 to use the holder-aware get/put API in unit-test stubs and callers. - Rework patch 2 documentation to describe holders as QOM objects or block exports, simplify the ref/unref descriptions, and use imperative function comments. - Identify block export holders with BlockExportOptions member id and rename the QAPI field to export-id. - Fix monitor cleanup so it only releases an AioContext acquired by that monitor, preventing an iothread_unref() assertion at shutdown. - Rebase the series onto the current upstream tree. ### V10 -> V9 Changelog - Rebase this series on the Daniel P. Berrangé's series: [PATCH v7 00/35] monitor: turn QMP and HMP into QOM objects https://lore.kernel.org/qemu-devel/20260706135824.2623960-1-berrange@redhat.com/ - Remove the monitor type of IOThreadHolder, make the monitor as a QOM object. - Remove GList related code and stays within QAPI instead of mixing GList and QAPI. - Fix missed comments in the patch 2. - Rewrite parts of commit log generated by AI. - Keep Stefan's reviewed-by in patch 2 and addressed Markus's comments. - Rewrite parts of code comments. - Drop original patch 6/7/8 for monitor parts. Zhang Chen (15): qapi/misc: Fix missed query-iothreads items iothread: introduce holder tracking iothread: add holder-aware AioContext accessors iothread: introduce iothread_unsafe_get_aio_context() block/export: track IOThread references monitor: track IOThread users with QOM paths virtio-vq-mapping: track iothread-vq-mapping references using device path virtio: track IOThread references for thread pinning net/colo: track IOThread references using path-based holder virtio-balloon: Update tracking iothread users with holder vfio-user/proxy: Update tracking iothread users with holder name xen-block: Update tracking iothread users with holder name monitor/hmp: display IOThread holders iothread: remove legacy iothread_get_aio_context() tests/unit/iothread: update AioContext ref/put helpers block/export/export.c | 62 ++++++++++++++--- blockdev.c | 2 +- hw/block/dataplane/xen-block.c | 19 +++++- hw/block/virtio-blk.c | 21 ++++-- hw/scsi/virtio-scsi-dataplane.c | 22 ++++-- hw/vfio-user/proxy.c | 16 ++++- hw/virtio/iothread-vq-mapping.c | 20 ++++-- hw/virtio/virtio-balloon.c | 22 ++++-- include/block/export.h | 5 ++ include/hw/virtio/iothread-vq-mapping.h | 6 +- include/system/iothread.h | 38 ++++++++++- iothread.c | 89 ++++++++++++++++++++++++- monitor/hmp-cmds.c | 20 ++++++ monitor/monitor-internal.h | 3 + monitor/monitor.c | 33 +++++++-- monitor/qmp.c | 5 +- net/colo-compare.c | 29 +++++--- qapi/misc.json | 86 ++++++++++++++++++++++-- tests/unit/iothread.c | 18 +++-- tests/unit/iothread.h | 7 +- tests/unit/test-aio-multithread.c | 5 +- tests/unit/test-bdrv-drain.c | 18 +++-- tests/unit/test-block-iothread.c | 21 ++++-- 23 files changed, 485 insertions(+), 82 deletions(-) -- 2.55.0