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Testing some workloads in two different scenarios, such as games running under Gamescope on a Steam Deck, or vkcube under a Plasma desktop, shows that in a significant portion of calls the dma_fence_unwrap_merge helper is called with just a single unsignalled fence. Therefore it is worthile to add a fast path for that case and so bypass the memory allocation and insertion sort attempts. Tested scenarios: 1) Hogwarts Legacy under Gamescope ~1500 calls per second to __dma_fence_unwrap_merge. Percentages per number of fences buckets, before and after checking for signalled status, sorting and flattening: N Before After 0 0.85% 1 69.80% -> The new fast path. 2-9 29.36% 9% (Ie. 91% of this bucket flattened to 1 fence) 10-19 20-40 50+ 2) Cyberpunk 2077 under Gamescope ~2400 calls per second. N Before After 0 0.71% 1 52.53% -> The new fast path. 2-9 44.38% 50.60% (Ie. half resolved to a single fence) 10-19 2.34% 20-40 0.06% 50+ 3) vkcube under Plasma 90 calls per second. N Before After 0 1 2-9 100% 0% (Ie. all resolved to a single fence) 10-19 20-40 50+ In the case of vkcube all invocations in the 2-9 bucket were actually just two input fences. v2: * Correct local variable name and hold on to unsignaled reference. (Chistian) Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com> Cc: Christian König <christian.koenig@amd.com> Cc: Friedrich Vock <friedrich.vock@gmx.de> Reviewed-by: Christian König <christian.koenig@amd.com> Signed-off-by: Christian König <christian.koenig@amd.com> Link: https://patchwork.freedesktop.org/patch/msgid/20241115102153.1980-4-tursulin@igalia.com
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 reStructuredText 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.