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This removes the usage of intel_ring_emit in favour of directly writing to the ring buffer. intel_ring_emit was preventing the compiler for optimising fetch and increment of the current ring buffer pointer and therefore generating very verbose code for every write. It had no useful purpose since all ringbuffer operations are started and ended with intel_ring_begin and intel_ring_advance respectively, with no bail out in the middle possible, so it is fine to increment the tail in intel_ring_begin and let the code manage the pointer itself. Useless instruction removal amounts to approximately two and half kilobytes of saved text on my build. Not sure if this has any measurable performance implications but executing a ton of useless instructions on fast paths cannot be good. v2: * Change return from intel_ring_begin to error pointer by popular demand. * Move tail increment to intel_ring_advance to enable some error checking. v3: * Move tail advance back into intel_ring_begin. * Rebase and tidy. v4: * Complete rebase after a few months since v3. v5: * Remove unecessary cast and fix !debug compile. (Chris Wilson) v6: * Make intel_ring_offset take request as well. * Fix recording of request postfix plus a sprinkle of asserts. (Chris Wilson) v7: * Use intel_ring_offset to get the postfix. (Chris Wilson) * Convert GVT code as well. v8: * Rename *out++ to *cs++. v9: * Fix GVT out to cs conversion in GVT. v10: * Rebase for new intel_ring_begin in selftests. Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Cc: Zhi Wang <zhi.a.wang@intel.com> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> Acked-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Link: http://patchwork.freedesktop.org/patch/msgid/20170214113242.29241-1-tvrtko.ursulin@linux.intel.com
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.