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92cd14408b
Frequent IOMMU remappings take about 50% of CPU usage because there is quite a lot to remap. Defer dmabuf's unmapping by 5 seconds in order to mitigate the mapping overhead which goes away completely and driver works as fast as in a case of a disabled IOMMU. The case of a disabled IOMMU should also benefit a tad from the caching since CPU cache maintenance that happens on dmabuf's attaching takes some resources. Signed-off-by: Dmitry Osipenko <digetx@gmail.com> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
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 Restructured Text 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.