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| author |   Vinicius Costa Gomes <vinicius.gomes@intel.com> | 2018-11-16 16:19:24 -0800 |
|---|---|---|
| committer |   Jeff Kirsher <jeffrey.t.kirsher@intel.com> | 2018-12-20 11:50:54 -0800 |
| commit | bad87ee82f74707913a27f16d40cd8a1c340b47e (patch) | |
| tree | a41754acfbd3c3407a3e498e7c843e00aa8b6112 /Documentation/networking/device_drivers | |
| parent | igb: Change RXPBSIZE size when setting Qav mode (diff) | |
| download | linux-dev-bad87ee82f74707913a27f16d40cd8a1c340b47e.tar.xz linux-dev-bad87ee82f74707913a27f16d40cd8a1c340b47e.zip | |
Documentation: igb: Add a section about CBS
Add some pointers to the definition of the CBS algorithm, and some
notes about the limits of its implementation in the i210 family of
controllers.
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Diffstat (limited to 'Documentation/networking/device_drivers')
| -rw-r--r-- | Documentation/networking/device_drivers/intel/igb.rst | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/Documentation/networking/device_drivers/intel/igb.rst b/Documentation/networking/device_drivers/intel/igb.rst index ba16b86d5593..e87a4a72ea2d 100644 --- a/Documentation/networking/device_drivers/intel/igb.rst +++ b/Documentation/networking/device_drivers/intel/igb.rst @@ -177,6 +177,25 @@ rate limit using the IProute2 tool. Download the latest version of the IProute2 tool from Sourceforge if your version does not have all the features you require. +Credit Based Shaper (Qav Mode) +------------------------------ +When enabling the CBS qdisc in the hardware offload mode, traffic shaping using +the CBS (described in the IEEE 802.1Q-2018 Section 8.6.8.2 and discussed in the +Annex L) algorithm will run in the i210 controller, so it's more accurate and +uses less CPU. + +When using offloaded CBS, and the traffic rate obeys the configured rate +(doesn't go above it), CBS should have little to no effect in the latency. + +The offloaded version of the algorithm has some limits, caused by how the idle +slope is expressed in the adapter's registers. It can only represent idle slopes +in 16.38431 kbps units, which means that if a idle slope of 2576kbps is +requested, the controller will be configured to use a idle slope of ~2589 kbps, +because the driver rounds the value up. For more details, see the comments on +:c:func:`igb_config_tx_modes()`. + +NOTE: This feature is exclusive to i210 models. + Support ======= |