### 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 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
* Atomic API Design: Merged iothread_get_aio_context and
iothread_ref_and_get_aio_context into a single unified function. The new
API enforces a 'holder' parameter, making "retrieval" and "tracking" an
atomic operation to prevent reference tracking leaks.
* Subsystem Integration: Fully migrated and adapted core modules including
Virtio (blk, vq-mapping, balloon, scsi), Block Layer (export, xen),
Network (COLO), VFIO, and the Monitor subsystem.
* Introspection: Expanded the IOThreadInfo QAPI structure to include a
'holders' array (list of QOM paths), accessible via both
query-iothreads (QMP) and info iothreads (HMP).
### V6 -> V7 Changelog
- Fixed comments issues in patch 02/14 (Thanks Markus).
- Removed redundant code.
- Rebased patches on upstream code.
- Fixed code conflict with latest patches.
- Added detailed description in git log and code.
- Added comments for patch 06/14 assuming the monitor is a QOM object,
Depends on Daniel Berrangé's RFC patch:
[PATCH RFC 00/17] monitor: turn QMP and HMP into QOM objects
### V5 -> V6 Changelog
* API Refactoring (Breaking Change):
- Implement the 'union': 'IoThreadHolder' for combine the QOM objects
and the block-node.
- Completely merged iothread_get_aio_context variants.
- The iothread_get_aio_context function now strictly requires a 'holder'
argument to ensure every context retrieval is accounted for.
* Expanded Module Coverage:
- Added holder tracking for the monitor subsystem (tracking threads used
by QMP/HMP).
- Added support for the virtio-scsi dataplane.
* Code Cleanup:
- Removed redundant and obsolete API declarations.
- Standardized the use of object_get_canonical_path() across all callers
to provide consistent and unique holder names.
* Bug Fixes:
- Updated qapi/misc.json documentation to fix missing descriptions in
query-iothreads items.
* Build System:
- Improved header inclusion logic to avoid redundant declaration errors
in unit tests.
* QAPI part:
- Sorry to drop the "Acked-by: Markus Armbruster <[email protected]>",
because this version have lots of changes in the:
[PATCH V6 13/14]qapi: examine IOThread attachment status via query-iothreads
Zhang Chen (14):
qapi/misc: Fix missed query-iothreads items
iothread: introduce iothread_ref/unref to track attached devices
iothread: tracking iothread users with holder name
blockdev: Update tracking iothread users with holder name
block/export: track IOThread reference in BlockExport
monitor: Update tracking iothread users with holder name
virtio-vq-mapping: track iothread-vq-mapping references using device
path
virtio: use iothread_get/put_aio_context for thread pinning
net/colo: track IOThread references using path-based holder
virtio-balloon: Update tracking iothread users with holder name
vfio-user/proxy: Update tracking iothread users with holder name
xen-block: Update tracking iothread users with holder name
qapi: examine IOThread attachment status via query-iothreads
iothread: simplify API by merging iothread_get_aio_context variants
block/export/export.c | 44 +++++++--
blockdev.c | 6 +-
hw/block/dataplane/xen-block.c | 10 ++-
hw/block/virtio-blk.c | 13 ++-
hw/scsi/virtio-scsi-dataplane.c | 13 ++-
hw/vfio-user/proxy.c | 7 +-
hw/virtio/iothread-vq-mapping.c | 11 ++-
hw/virtio/virtio-balloon.c | 14 +--
include/block/block_int-common.h | 5 ++
include/block/export.h | 6 ++
include/hw/virtio/iothread-vq-mapping.h | 6 +-
include/system/iothread.h | 9 +-
iothread.c | 113 +++++++++++++++++++++++-
monitor/hmp-cmds.c | 22 +++++
monitor/monitor-internal.h | 3 +
monitor/monitor.c | 24 ++++-
monitor/qmp.c | 3 +-
net/colo-compare.c | 18 ++--
qapi/misc.json | 71 ++++++++++++++-
19 files changed, 342 insertions(+), 56 deletions(-)
--
2.49.0
