f7ed83cc19
We treat idling the GT (intel_rps_park) as a downclock event, and reduce
the frequency we intend to restart the GT with. Since the two workloads
are likely related (e.g. a compositor rendering every 16ms), we want to
carry the frequency and load information from across the idling.
However, we do also need to update the frequencies so that workloads
that run for less than 1ms are autotuned by RPS (otherwise we leave
compositors running at max clocks, draining excess power). Conversely,
if we try to run too slowly, the next workload has to run longer. Since
there is a hysteresis in the power graph, below a certain frequency
running a short workload for longer consumes more energy than running it
slightly higher for less time. The exact balance point is unknown
beforehand, but measurements with 30fps media playback indicate that RPe
is a better choice.
Reported-by: Edward Baker <edward.baker@intel.com>
Tested-by: Edward Baker <edward.baker@intel.com>
Fixes: 043cd2d14ede ("drm/i915/gt: Leave rps->cur_freq on unpark")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Edward Baker <edward.baker@intel.com>
Cc: Andi Shyti <andi.shyti@intel.com>
Cc: Lyude Paul <lyude@redhat.com>
Cc: <stable@vger.kernel.org> # v5.8+
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201124183521.28623-1-chris@chris-wilson.co.uk
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.