APT 3.3.5 speeds up dependency resolution 10-20%, cuts page faults 65%

The APT package manager, which underpins software installation on Debian, Ubuntu, and derivative distributions, has released version 3.3.5 with targeted performance and architectural improvements. The update delivers 10-20% faster dependency resolution in the solver subsystem and reduces page faults by 65%, though these gains apply specifically to solver computation rather than download or installation throughput. The release also extracts the SAT solver core into a separate component and standardizes how unprotected package removals are handled across internal solver behavior and API.

Repository signing-key management sees significant changes: APT 3.3.5 deprecates fingerprint-based Signed-By configuration in favor of direct keyring file references, and drops support for Signed-By declarations embedded in repository Release files. These changes primarily impact distribution maintainers and administrators managing third-party repositories. The release also introduces expanded performance logging with counters for stalled CPU cycles, TLB activity, page faults, and scheduling events, plus a new perf-eval.py analysis tool for developers.

Solver performance and signing-key architecture changes

• SAT solver extraction: The dependency solver's core has been refactored into a standalone component, separating it from the main APT codebase for cleaner maintenance and potential reuse.
• Performance metrics: Dependency resolution benchmarks show 10-20% speed improvement alongside a 65% reduction in page faults, though the changelog explicitly limits these figures to solver operations rather than end-to-end package operations.
• Signing-key deprecation: Fingerprint-based Signed-By configuration is deprecated in favor of keyring file paths; embedded Signed-By in Release files is removed entirely, shifting trust anchor management to explicit filesystem references.
• Behavioral consistency: Unprotected package removals now behave identically between APT's internal solver and its external API, resolving a prior implementation discrepancy.
• Performance instrumentation: New kernel-level counters track stalled cycles, DTLB/ITLB activity, page faults, and scheduler events, with a dedicated perf-eval.py script for log analysis and regression detection.

Why it matters

For Debian-based distributions, the solver optimizations will eventually reduce CPU overhead during complex upgrade operations, particularly on systems with large package sets or constrained memory. The signing-key changes push maintainers toward more auditable, filesystem-based trust management but will require migration work for third-party repository operators before the deprecated fingerprint syntax is removed in future releases.