Hi, I've merged the Nix `fast-eval' branch into the trunk. This replaces the current Nix expression evaluator by a new, faster implementation. It no longer uses the term-rewriting based approach (described in ) but a more conventional functional language implementation based on thunk updating. As a result, Nix no longer depends on the ATerm library.
Here are some benchmark results to show the performance improvement. The benchmarks are: - `nix-env -f /etc/nixos/nixpkgs -qa \*' on Nixpkgs r21747. - `nix-env -f /etc/nixos/nixpkgs -qa \* --drv-path'. - `nix-instantiate /etc/nixos/nixos -A system --readonly-mode' (also on r21747 of NixOS). This is what every `nixos-rebuild' operation does. - `nix-instantiate /etc/nixos/nixos/tests/ -A proxy.test --readonly-mode' (which evaluates 4 NixOS system configurations). These were done on a 32-bit Linux machine (Intel Core 2 Duo T7700 @ 2.40GHz, 2 GiB RAM) and on a 64-bit Linux machine (Intel Core i5 750 @ 2.67GHz, 6 GiB RAM). Here are the timings in seconds: | Old | New | Speedup -----------------------------------------+-------+------+-------- `nix-env -qa' (32-bit) | 2.96 | 0.60 | 4.9x `nix-env -qa' (64-bit) | 1.86 | 0.32 | 5.8x `nix-env -qa --drv-path' (32-bit) | 12.48 | 3.96 | 3.2x `nix-env -qa --drv-path' (64-bit) | 7.65 | 2.04 | 3.8x `nix-instantiate -A system' (32-bit) | 6.79 | 1.32 | 5.1x `nix-instantiate -A system' (64-bit) | 4.63 | 0.71 | 6.5x `nix-instantiate -A proxy.test' (32-bit) | 23.86 | 3.55 | 6.7x `nix-instantiate -A proxy.test' (64-bit) | 15.76 | 1.95 | 8.1x Another goal of the `fast-eval' branch was to reduce memory consumption by the evaluator. The old evaluator basically never released memory due to its normal form cache. With the new evaluator, we can in principle reclaim garbage memory. However, it doesn't actually have a garbage collector yet. I intend to use the Boehm GC for that. Nevertheless, the new evaluator already uses less memory than the old one. For instance, `nix-instantiate -A system' on 64-bit Linux uses 358.6 MiB with the old evaluator, but only 213.7 MiB with the new evaluator (according to Valgrind's `massif' tool).  http://www.st.ewi.tudelft.nl/~dolstra/pubs/laziness-ldta2008-final.pdf -- Eelco Dolstra | http://www.st.ewi.tudelft.nl/~dolstra/ _______________________________________________ nix-dev mailing list firstname.lastname@example.org https://mail.cs.uu.nl/mailman/listinfo/nix-dev