Fork of alistair23 Linux kernel for reMarkable from https://github.com/alistair23/linux
c9e0c6da53
Currently the timer is armed for 1ms after the first use and is killed immediately, dropping the forcewake as early as possible. However, for very frequent operations the forcewake dance has a large impact on latency and keeping the timer alive until we are idle is preferred. To achieve this, if we call intel_uncore_forcewake_get whilst the timer is alive (repeated use), then set a flag to restart the timer on expiry rather than drop the forcewake usage count. The timer is racy, the consequence of the race is to expire the timer earlier than is now desired but does not impact on correct behaviour. The offset the race slightly, we set the active flag again on intel_uncore_forcewake_put. The effect should be to reduce the jitter of reacquiring the fw every 1ms on a busy system. However, the cost is to keep the timer alive for an extra 1ms on a nearly idle system. We chose to incur the jitter previously to keep the timer off for as much as possible. Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Mika Kuoppala <mika.kuoppala@intel.com> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Link: http://patchwork.freedesktop.org/patch/msgid/20170526132209.14640-1-chris@chris-wilson.co.uk |
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Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.