### 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.
### V17 -> V16 Changelog
- Rebase code to resolve code conflicts for patch 8:
"virtio-balloon: Update tracking iothread users with holder".
This issue caused by latest merged patch "fdc3f9a83d".
### V16 -> V15 Changelog
- Unified per-monitor IOThread checks and accesses through
mon->iothread after initialization.
- Simplified PATCH 13's commit message and clarified why blockdev
cannot use the holder-aware get/put APIs.
- Dropped the v15 Patch 1 in this series, It will be taken away
independently by trivial-patches tree.
### V15 -> V14 Changelog
- Moved monitor IOThread cleanup from unparent() to monitor_finalize(),
pairing complete() with instance finalization.
- Squashed V14 PATCH 04 and PATCH 14 into PATCH 13 and clarified the
blockdev lifetime assumption. Since the additional changes are minimal,
PATCH 13 retains Stefan's Reviewed-by from V14 PATCH 04.
- Rebased and adapted info iothreads to the MonitorHMP interface.
### 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.
Zhang Chen (13):
iothread: introduce holder tracking
iothread: add holder-aware AioContext accessors
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: make legacy AioContext getter explicitly unsafe
tests/unit/iothread: update AioContext ref/put helpers
block/export/export.c | 62 +++++++++++++---
blockdev.c | 9 ++-
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 | 21 ++++--
include/block/export.h | 5 ++
include/hw/virtio/iothread-vq-mapping.h | 6 +-
include/hw/virtio/virtio-balloon.h | 1 +
include/system/iothread.h | 38 +++++++++-
iothread.c | 89 ++++++++++++++++++++++-
monitor/hmp-cmds.c | 20 ++++++
monitor/monitor-internal.h | 7 +-
monitor/monitor.c | 36 +++++++---
monitor/qmp.c | 14 ++--
net/colo-compare.c | 29 +++++---
qapi/misc.json | 94 +++++++++++++++++++++----
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 ++++--
24 files changed, 496 insertions(+), 102 deletions(-)
--
2.43.0
