Re: [PATCH 0/3] ceph: add subvolume metrics reporting support

[Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>]

On Thu, 2025-11-27 at 13:46 +0000, Alex Markuze wrote:
> This patch series adds support for per-subvolume I/O metrics collection
> and reporting to the MDS. This enables administrators to monitor I/O
> patterns at the subvolume granularity, which is useful for multi-tenant
> CephFS deployments where different subvolumes may be allocated to
> different users or applications.
> 
> The implementation requires protocol changes to receive the subvolume_id
> from the MDS (InodeStat v9), and introduces a new metrics type
> (CLIENT_METRIC_TYPE_SUBVOLUME_METRICS) for reporting aggregated I/O
> statistics back to the MDS.
> 
> Patch 1 adds forward-compatible handling for InodeStat v8. The MDS v8
> encoding added a versioned optmetadata field containing optional inode

What is "optmetadata"? Do you mean "opt metadata" here? Does it exact name of
the field?

Thanks,
Slava.

> metadata such as charmap (for case-insensitive/case-preserving file
> systems). The kernel client does not currently support case-insensitive
> lookups, so this field is skipped rather than parsed. This ensures
> forward compatibility with newer MDS servers without requiring the
> full case-insensitivity feature implementation.
> 
> Patch 2 adds support for parsing the subvolume_id field from InodeStat
> v9 and storing it in the inode structure for later use.
> 
> Patch 3 adds the complete subvolume metrics infrastructure:
> - CEPHFS_FEATURE_SUBVOLUME_METRICS feature flag for MDS negotiation
> - Red-black tree based metrics tracker for efficient per-subvolume
>   aggregation
> - Wire format encoding matching the MDS C++ AggregatedIOMetrics struct
> - Integration with the existing CLIENT_METRICS message
> - Recording of I/O operations from file read/write and writeback paths
> - Debugfs interfaces for monitoring
> 
> Metrics tracked per subvolume include:
> - Read/write operation counts
> - Read/write byte counts
> - Read/write latency sums (for average calculation)
> 
> The metrics are periodically sent to the MDS as part of the existing
> metrics reporting infrastructure when the MDS advertises support for
> the SUBVOLUME_METRICS feature.
> 
> Debugfs additions in Patch 3:
> - metrics/subvolumes: displays last sent and pending subvolume metrics
> - metrics/metric_features: displays MDS session feature negotiation
>   status, showing which metric-related features are enabled (including
>   METRIC_COLLECT and SUBVOLUME_METRICS)
> 
> Alex Markuze (3):
>   ceph: handle InodeStat v8 versioned field in reply parsing
>   ceph: parse subvolume_id from InodeStat v9 and store in inode
>   ceph: add subvolume metrics collection and reporting
> 
>  fs/ceph/Makefile            |   2 +-
>  fs/ceph/addr.c              |  10 +
>  fs/ceph/debugfs.c           | 153 ++++++++++++++
>  fs/ceph/file.c              |  58 ++++-
>  fs/ceph/inode.c             |  19 ++
>  fs/ceph/mds_client.c        |  89 ++++++--
>  fs/ceph/mds_client.h        |  14 +-
>  fs/ceph/metric.c            | 172 ++++++++++++++-
>  fs/ceph/metric.h            |  27 ++-
>  fs/ceph/subvolume_metrics.c | 407 ++++++++++++++++++++++++++++++++++++
>  fs/ceph/subvolume_metrics.h |  68 ++++++
>  fs/ceph/super.c             |   1 +
>  fs/ceph/super.h             |   3 +
>  13 files changed, 997 insertions(+), 26 deletions(-)
>  create mode 100644 fs/ceph/subvolume_metrics.c
>  create mode 100644 fs/ceph/subvolume_metrics.h