[PATCH v3 0/2] nvme-tcp: NIC topology aware I/O queue scaling and queue info export

[Nilay Shroff]

This patch series has been revised based on feedback from the netdev
community [1].

Following the feedback, the logic for determining the number of fabric I/O
queues (nr-io-queues) has been moved to userspace in nvme-cli [2]. As a
result, the first two patches from the previous series, which implemented
this logic in the kernel driver, have been dropped. This series contains
the remaining two patches, which export NVMe/TCP I/O queue information
through debugfs to facilitate host-side network tuning.

The first patch introduces debugfs helper functions that can be used by
drivers to export debugfs attributes. 

The second patch exports NVMe/TCP I/O queue and TCP flow information through
debugfs. For each I/O queue, it provides:
   - queue id (qid)
   - CPU affinity
   - TCP flow (src/dst IP and ports)

This enables userspace tools to configure:
   - IRQ affinity
   - RPS/XPS
   - ntuple steering
   - or any other scaling as deemed feasible

Together with tunning, these changes allow better alignment of:
   flow -> NIC queue -> IRQ -> CPU -> NVMe/TCP I/O worker

Improving this alignment can enhance flow-to-CPU locality, potentially
improving performance and reducing I/O latency. Performance evaluation
results comparing the baseline with the tuned configuration are
available in [3].

Thanks!

[1]: https://lore.kernel.org/all/20260807160904.2eb1b3d1@kernel.org/
[2]: https://github.com/linux-nvme/nvme-cli/pull/4140
[3]: https://lore.kernel.org/all/20260731073918.614014-1-nilay@linux.ibm.com/

Changes from v2
  - Dropped patch #1 and #2 from v2
  - Added new debugfs attribute parameter "is_visible" which could be useful
    to hide the attribute for certain configuration or transport. 
Link to v2: https://lore.kernel.org/all/20260731073918.614014-1-nilay@linux.ibm.com/

Nilay Shroff (2):
  nvme: add debugfs helpers for NVMe drivers
  nvme: expose queue information via debugfs

 drivers/nvme/host/Makefile  |   2 +-
 drivers/nvme/host/core.c    |   3 +
 drivers/nvme/host/debugfs.c | 207 ++++++++++++++++++++++++++++++++++++
 drivers/nvme/host/nvme.h    |  12 +++
 drivers/nvme/host/tcp.c     |  54 ++++++++++
 5 files changed, 277 insertions(+), 1 deletion(-)
 create mode 100644 drivers/nvme/host/debugfs.c

-- 
2.53.0