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| author | pennae <github@quasiparticle.net> | 2021-12-20 13:28:54 +0100 |
|---|---|---|
| committer | pennae <github@quasiparticle.net> | 2021-12-20 23:01:28 +0100 |
| commit | 09b245690a9ab40847e3faa96646e4bd6ce033e0 (patch) | |
| tree | 426d9a6c71141f027316e3aba1e408fb6f0b2865 /src/libexpr/eval.hh | |
| parent | 6e6e998930f0d7361d64644eb37d9134e74e8501 (diff) | |
bulk-allocate Value instances in the evaluator
calling GC_malloc for each value is significantly more expensive than
allocating a bunch of values at once with GC_malloc_many. "a bunch" here
is a GC block size, ie 16KiB or less.
this gives a 1.5% performance boost when evaluating our nixos system.
tested with
nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
# on master
Time (mean ± σ): 3.335 s ± 0.007 s [User: 2.774 s, System: 0.293 s]
Range (min … max): 3.315 s … 3.347 s 50 runs
# with this change
Time (mean ± σ): 3.288 s ± 0.006 s [User: 2.728 s, System: 0.292 s]
Range (min … max): 3.274 s … 3.307 s 50 runs
Diffstat (limited to 'src/libexpr/eval.hh')
| -rw-r--r-- | src/libexpr/eval.hh | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh index 1aab8e166..cc63294c6 100644 --- a/src/libexpr/eval.hh +++ b/src/libexpr/eval.hh @@ -133,6 +133,9 @@ private: /* Cache used by prim_match(). */ std::shared_ptr<RegexCache> regexCache; + /* Allocation cache for GC'd Value objects. */ + void * valueAllocCache = nullptr; + public: EvalState( |