6b567085c1
Originally we would enable and disable the breadcrumb interrupt
immediately on demand. This was slow enough to have a large impact
(>30%) on tasks that hopped between engines. However, by using a shadow
to keep the irq alive for an extra interrupt (see commit 67b807a89230
("drm/i915: Delay disabling the user interrupt for breadcrumbs")) and
by recently reducing the cost in adding ourselves to the signal tree, we
no longer need to spin-request during await_request to avoid delays in
throughput tests. Without the earlier patches to stop the wakeup when
signaling if the irq was already active, we saw no improvement in
execbuf overhead (and corresponding contention in other clients) despite
the removal of the spinner in a simple test like glxgears. This means
there will be scenarios where now we spend longer enabling the interrupt
than we would have spent spinning, but these are not likely to have as
noticeable an impact as the high frequency test cases (where there
should not be any regression).
Ulterior motive: generalising the engine->sync_to to handle different
types of semaphores and non-semaphores.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Oscar Mateo <oscar.mateo@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170608111405.16466-4-chris@chris-wilson.co.uk
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.