bac24f59f4
When we introduced preemption, we chose to keep it disabled for gen8 as supporting preemption inside GPGPU user batches required various w/a in userspace. Since then, the desire to preempt long queues of requests between batches (e.g. within busywaiting semaphores) has grown. So allow arbitration within the busywaits and between requests, but disable arbitration within user batches so that we can preempt between requests and not risk breaking GPGPU. However, since this preemption is much coarser and doesn't interfere with userspace, we decline to include it amongst the scheduler capabilities. (This is also required for us to skip over the preemption selftests that expect to be able to preempt user batches.) Michal suggested that we could perhaps allow preemption inside gen8 userspace batches if we can satisfy ourselves that the default preemption settings are viable with existing userspace (principally OpenCL which already should carry any known workaround). We could then merge the two code paths back into one, even dropping the artifical has-preemption device feature flag. Testcase: igt/gem_exec_scheduler/semaphore-user References: |
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README
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.