[RFC PATCHv5 7/7] nvme-multipath: add documentation for adaptive I/O policy

Nilay Shroff
2025-11-05T10:34:25Z

Update the nvme-multipath documentation to describe the adaptive I/O
policy, its behavior, and when it is suitable for use.

Suggested-by: Guixin Liu <kanie@linux.alibaba.com>
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
---
Documentation/admin-guide/nvme-multipath.rst | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)

diff --git a/Documentation/admin-guide/nvme-multipath.rst b/Documentation/admin-guide/nvme-multipath.rst
index 97ca1ccef459..7befaab01cf5 100644
--- a/Documentation/admin-guide/nvme-multipath.rst
+++ b/Documentation/admin-guide/nvme-multipath.rst
@@ -70,3 +70,22 @@ When to use the queue-depth policy:
1. High load with small I/Os: Effectively balances load across paths when
the load is high, and I/O operations consist of small, relatively
fixed-sized requests.
+
+Adaptive
+--------
+
+The adaptive policy manages I/O requests based on path latency. It periodically
+calculates a weight for each path and distributes I/O accordingly. Paths with
+higher latency receive lower weights, resulting in fewer I/O requests being sent
+to them, while paths with lower latency handle a proportionally larger share of
+the I/O load.
+
+When to use the adaptive policy
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+1. Homogeneous Path Performance: Utilizes all available paths efficiently when
+ their performance characteristics (e.g., latency, bandwidth) are similar.
+
+2. Heterogeneous Path Performance: Dynamically distributes I/O based on per-path
+ performance characteristics. Paths with lower latency receive a higher share
+ of I/O compared to those with higher latency.
--
2.51.0