doc: add PMD power management errata with RTM and GCC 9

An errata exists where users may see reduced power savings when using
PMD Power Management. This issue occurs when compiling DPDK applications
with GCC-9 on platforms with TSX enabled. In rte_power_monitor_multi(),
the function may return without successfully starting the RTM
transaction (the _xbegin() fails).

Signed-off-by: David Hunt <david.hunt@intel.com>

diff --git a/doc/guides/rel_notes/release_22_03.rst b/doc/guides/rel_notes/release_22_03.rst
index d231e3e8a4ed12408227ce37065e9697d01df0d6..5ad9ea3728d708cb088fda3d424fc61321182d3c 100644 (file)
--- a/doc/guides/rel_notes/release_22_03.rst
+++ b/doc/guides/rel_notes/release_22_03.rst
@@ -313,6 +313,18 @@ Known Issues
    Also, make sure to start the actual text at the margin.
    =======================================================
 
+* **Possible reduced power saving with PMD Power Management.**
+
+  Users may see reduced power savings when using PMD Power Management.
+  This issue occurs when compiling DPDK applications with GCC-9
+  on platforms with TSX enabled.
+  The function ``rte_power_monitor_multi()`` may return
+  without successfully starting the RTM transaction (``_xbegin()`` fails).
+
+  There are three workarounds for this issue.
+  Either build DPDK with GCC-11 or newer, build with shared libraries,
+  or build DPDK with fewer drivers.
+
 
 Tested Platforms
 ----------------