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Print the accumulated runtime for client when printing fdinfo. Each time a query is done it first does 2 things: 1) loop through all the exec queues for the current client and accumulate the runtime, per engine class. CTX_TIMESTAMP is used for that, being read from the context image. 2) Read a "GPU timestamp" that can be used for considering "how much GPU time has passed" and that has the same unit/refclock as the one recording the runtime. RING_TIMESTAMP is used for that via MMIO. Since for all current platforms RING_TIMESTAMP follows the same refclock, just read it once, using any first engine available. This is exported to userspace as 2 numbers in fdinfo: drm-cycles-<class>: <RUNTIME> drm-total-cycles-<class>: <TIMESTAMP> Userspace is expected to collect at least 2 samples, which allows to know the client engine busyness as per: RUNTIME1 - RUNTIME0 busyness = --------------------- T1 - T0 Since drm-cycles-<class> always starts at 0, it's also possible to know if and engine was ever used by a client. It's expected that userspace will read any 2 samples every few seconds. Given the update frequency of the counters involved and that CTX_TIMESTAMP is 32-bits, the counter for each exec_queue can wrap around (assuming 100% utilization) after ~200s. The wraparound is not perceived by userspace since it's just accumulated for all the exec_queues in a 64-bit counter) but the measurement will not be accurate if the samples are too far apart. This could be mitigated by adding a workqueue to accumulate the counters every so often, but it's additional complexity for something that is done already by userspace every few seconds in tools like gputop (from igt), htop, nvtop, etc, with none of them really defaulting to 1 sample per minute or more. Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com> Acked-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com> Link: https://patchwork.freedesktop.org/patch/msgid/20240517204310.88854-9-lucas.demarchi@intel.com Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
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11 lines
266 B
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.. SPDX-License-Identifier: GPL-2.0+
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.. _xe-usage-stats:
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========================================
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Xe DRM client usage stats implementation
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========================================
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.. kernel-doc:: drivers/gpu/drm/xe/xe_drm_client.c
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:doc: DRM Client usage stats
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