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Chris Wilson
67b807a892
A significant cost in setting up a wait is the overhead of enabling the interrupt. As we disable the interrupt whenever the queue of waiters is empty, if we are frequently waiting on alternating batches, we end up re-enabling the interrupt on a frequent basis. We do want to disable the interrupt during normal operations as under high load it may add several thousand interrupts/s - we have been known in the past to occupy whole cores with our interrupt handler after accidentally leaving user interrupts enabled. As a compromise, leave the interrupt enabled until the next IRQ, or the system is idle. This gives a small window for a waiter to keep the interrupt active and not be delayed by having to re-enable the interrupt. v2: Restore hangcheck/missed-irq detection for continuations v3: Be more careful restoring the hangcheck timer after reset v4: Be more careful restoring the fake irq after reset (if required!) v5: Redo changes to intel_engine_wakeup() v6: Factor out __intel_engine_wakeup() v7: Improve commentary for declaring a missed wakeup Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Link: http://patchwork.freedesktop.org/patch/msgid/20170227205850.2828-4-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.