[PATCH v2 3/3] nvme: document the service-time iopolicy sysfs attributes

[Guixin Liu <kanie@linux.alibaba.com>]

The service-time iopolicy adds two sysfs attributes to the NVMe path
namespace devices: in_flight_bytes, reporting the bytes currently in
flight on the path's controller, and relative_throughput, the
per-path throughput weight used by the service-time estimation.

Document both in the stable sysfs ABI, including the 0-100 value
range, the default of 1, and the standby semantics of a
relative_throughput of 0.

Signed-off-by: Guixin Liu <kanie@linux.alibaba.com>
---
 Documentation/ABI/stable/sysfs-nvme | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/Documentation/ABI/stable/sysfs-nvme b/Documentation/ABI/stable/sysfs-nvme
index a2f5d0710db40..adaf292c8c67b 100644
--- a/Documentation/ABI/stable/sysfs-nvme
+++ b/Documentation/ABI/stable/sysfs-nvme
@@ -326,6 +326,28 @@ Description:
 		currently selected path. Returns empty if iopolicy is not
 		"numa". Requires CONFIG_NVME_MULTIPATH.
 
+What:		/sys/block/nvmeXcYnZ/in_flight_bytes
+What:		/sys/block/nvmeXcYnZ/relative_throughput
+Date:		October 2026
+KernelVersion:	7.5
+Contact:	Guixin Liu <kanie@linux.alibaba.com>
+Description:
+		in_flight_bytes: Shows the number of bytes currently in
+		flight on this path's controller. Returns empty if
+		iopolicy is not "service-time".
+		Requires CONFIG_NVME_MULTIPATH.
+
+		relative_throughput: Shows or sets the relative
+		throughput weight of this path, which the "service-time"
+		iopolicy uses to estimate the path service time as
+		in_flight_bytes / relative_throughput. The value is an
+		integer in the range 0-100 and defaults to 1; assign
+		higher values to faster paths. A path with a value of 0
+		is only selected when no path with a positive value is
+		available. Reading returns empty if iopolicy is not
+		"service-time"; writing is accepted regardless of the
+		active policy. Requires CONFIG_NVME_MULTIPATH.
+
 What:		/sys/block/nvmeXnY/delayed_removal_secs
 Date:		May 2025
 KernelVersion:	6.16
-- 
2.43.7