linux-kernel - [PATCH net-next] docs: networking: clarify expectation of persistent stats

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Message-ID: <20250825134755.3468861-1-naveenm@marvell.com>
Date: Mon, 25 Aug 2025 19:17:55 +0530
From: Naveen Mamindlapalli <naveenm@...vell.com>
To: <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
        <pabeni@...hat.com>, <horms@...nel.org>, <corbet@....net>,
        <andrew@...n.ch>
CC: <netdev@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Naveen Mamindlapalli <naveenm@...vell.com>
Subject: [PATCH net-next] docs: networking: clarify expectation of persistent stats

This update clarifies the requirement for preserving statistics across
interface up/down cycles, noting that some drivers may not support this
due to inherent limitations. It also outlines the potential effects on
monitoring and observability tools.

Signed-off-by: Naveen Mamindlapalli <naveenm@...vell.com>
---
 Documentation/networking/statistics.rst | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/Documentation/networking/statistics.rst b/Documentation/networking/statistics.rst
index 518284e287b0..857b08d633f7 100644
--- a/Documentation/networking/statistics.rst
+++ b/Documentation/networking/statistics.rst
@@ -222,8 +222,18 @@ Retrieving ethtool statistics is a multi-syscall process, drivers are advised
 to keep the number of statistics constant to avoid race conditions with
 user space trying to read them.
 
-Statistics must persist across routine operations like bringing the interface
-down and up.
+Statistics are expected to persist across routine operations like bringing the
+interface down and up. This includes both standard interface statistics and
+driver-defined statistics reported via `ethtool -S`.
+
+However, this behavior is not always strictly followed, and some drivers do
+reset these counters to zero when the device is closed and reopened. This can
+lead to misinterpretation of network behavior by monitoring tools, such as
+SNMP, that expect monotonically increasing counters.
+
+Driver authors are expected to preserve statistics across interface down/up
+cycles to ensure consistent reporting and better integration with monitoring
+tools that consume these statistics.
 
 Kernel-internal data structures
 -------------------------------
-- 
2.34.1