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a0e047156c
Our existing behaviour is to allow contexts and their GPU requests to persist past the point of closure until the requests are complete. This allows clients to operate in a 'fire-and-forget' manner where they can setup a rendering pipeline and hand it over to the display server and immediately exit. As the rendering pipeline is kept alive until completion, the display server (or other consumer) can use the results in the future and present them to the user. The compute model is a little different. They have little to no buffer sharing between processes as their kernels tend to operate on a continuous stream, feeding the results back to the client application. These kernels operate for an indeterminate length of time, with many clients wishing that the kernel was always running for as long as they keep feeding in the data, i.e. acting like a DSP. Not all clients want this persistent "desktop" behaviour and would prefer that the contexts are cleaned up immediately upon closure. This ensures that when clients are run without hangchecking (e.g. for compute kernels of indeterminate runtime), any GPU hang or other unexpected workloads are terminated with the process and does not continue to hog resources. The default behaviour for new contexts is the legacy persistence mode, as some desktop applications are dependent upon the existing behaviour. New clients will have to opt in to immediate cleanup on context closure. If the hangchecking modparam is disabled, so is persistent context support -- all contexts will be terminated on closure. We expect this behaviour change to be welcomed by compute users, who have often been caught between a rock and a hard place. They disable hangchecking to avoid their kernels being "unfairly" declared hung, but have also experienced true hangs that the system was then unable to clean up. Naturally, this leads to bug reports. Testcase: igt/gem_ctx_persistence Link: https://github.com/intel/compute-runtime/pull/228 Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Cc: Michał Winiarski <michal.winiarski@intel.com> Cc: Jon Bloomfield <jon.bloomfield@intel.com> Reviewed-by: Jon Bloomfield <jon.bloomfield@intel.com> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Acked-by: Jason Ekstrand <jason@jlekstrand.net> Link: https://patchwork.freedesktop.org/patch/msgid/20191029202338.8841-1-chris@chris-wilson.co.uk |
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