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The latency of each EMAD can be measured by firmware. The driver can get the measurement via latency TLV which can be added to each EMAD. This TLV is optional, when EMAD is sent with this TLV, the EMAD's response will include the TLV and the field 'latency_time' will contain the firmware measurement. This information can be processed using BPF program for example, to create a histogram and average of the latency per register. In addition, it is possible to measure the end-to-end latency, and then reduce firmware measurement, which will result in the latency of the software overhead. This information can be useful to improve the driver performance. Add support for latency TLV by default for all EMADs. First we planned to enable latency TLV per demand, using devlink-param. After some tests, we know that the usage of latency TLV does not impact the end-to-end latency, so it is OK to enable it by default. Note that similar to string TLV, the latency TLV is not supported in all firmware versions. Enable the usage of this TLV only after verifying it is supported by the current firmware version by querying the Management General Information Register (MGIR). Signed-off-by: Danielle Ratson <danieller@nvidia.com> Signed-off-by: Amit Cohen <amcohen@nvidia.com> Reviewed-by: Ido Schimmel <idosch@nvidia.com> Signed-off-by: Petr Machata <petrm@nvidia.com> Reviewed-by: Tony Nguyen <anthony.l.nguyen@intel.com> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.