Claude review: Fair(er) DRM scheduler

[Claude Code Review Bot <claude-review@example.com>]

Overall Series Review

Subject: Fair(er) DRM scheduler
Author: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Patches: 31
Reviewed: 2026-03-09T08:37:18.150766

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This is a well-structured, v7 series by Tvrtko Ursulin that replaces the existing FIFO and round-robin scheduling policies in the DRM GPU scheduler with a new CFS-inspired "fair" scheduling algorithm based on virtual runtime. The series is mature, with acks from Danilo Krummrich and reviews from multiple maintainers across the affected subsystems.

**Strengths:**
- Clear progression: cleanups/consolidation first, then the new algorithm, then removal of old code and simplification
- Extensive unit tests added before the algorithm changes
- Well-documented commit messages explaining design trade-offs (particularly the GPU time accounting placement rationale in patch 8)
- The splitting point at patch 12 is well-chosen for staged merge strategy
- Comprehensive benchmarking data in the cover letter
- Clean removal of `num_rqs` across all drivers at the end

**Concerns:**
- The `container_of(entity->rq, typeof(*sched), rq)` pattern introduced in patch 14 is verbose and appears many times across amdgpu code. Worth noting but this is inherent to the embedding approach.
- The `drm_sched_entity_stats` lock granularity could be a future contention point under heavy workloads with many entities, though the current design is reasonable for now.

Overall, the series is in good shape and the approach is sound.

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