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cache singleton Envs just like Values

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vast majority of envs is this size.

before:

  Benchmark 1: nix flakes search --no-eval-cache --offline ../nixpkgs hello
    Time (mean ± σ):      6.946 s ±  0.041 s    [User: 5.875 s, System: 0.835 s]
    Range (min … max):    6.834 s …  7.005 s    20 runs

  Benchmark 2: nix flakes eval -f ../nixpkgs/pkgs/development/haskell-modules/hackage-packages.nix
    Time (mean ± σ):     330.3 ms ±   2.5 ms    [User: 299.2 ms, System: 30.9 ms]
    Range (min … max):   327.5 ms … 337.7 ms    20 runs

  Benchmark 3: nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
    Time (mean ± σ):      2.671 s ±  0.035 s    [User: 2.370 s, System: 0.232 s]
    Range (min … max):    2.597 s …  2.749 s    20 runs

after:

  Benchmark 1: nix flakes search --no-eval-cache --offline ../nixpkgs hello
    Time (mean ± σ):      6.935 s ±  0.052 s    [User: 5.852 s, System: 0.853 s]
    Range (min … max):    6.808 s …  7.026 s    20 runs

  Benchmark 2: nix flakes eval -f ../nixpkgs/pkgs/development/haskell-modules/hackage-packages.nix
    Time (mean ± σ):     329.8 ms ±   2.7 ms    [User: 299.0 ms, System: 30.8 ms]
    Range (min … max):   326.6 ms … 336.5 ms    20 runs

  Benchmark 3: nix flakes eval --raw --impure --file expr.nix
    Time (mean ± σ):      2.655 s ±  0.038 s    [User: 2.364 s, System: 0.220 s]
    Range (min … max):    2.574 s …  2.737 s    20 runs
This commit is contained in:
pennae 2021-12-26 19:32:08 +01:00
parent 4b2b0d3a55
commit 60ed4e908a
2 changed files with 23 additions and 1 deletions
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21
src/libexpr/eval.cc
View file

@ -438,8 +438,10 @@ EvalState::EvalState(
, regexCache(makeRegexCache())
#if HAVE_BOEHMGC
, valueAllocCache(std::allocate_shared<void *>(traceable_allocator<void *>(), nullptr))
, env1AllocCache(std::allocate_shared<void *>(traceable_allocator<void *>(), nullptr))
#else
, valueAllocCache(std::make_shared<void *>(nullptr))
, env1AllocCache(std::make_shared<void *>(nullptr))
#endif
, baseEnv(allocEnv(128))
, staticBaseEnv(false, 0)
@ -892,7 +894,24 @@ Env & EvalState::allocEnv(size_t size)
{
nrEnvs++;
nrValuesInEnvs += size;
Env * env = (Env *) allocBytes(sizeof(Env) + size * sizeof(Value *));
Env * env;
if (size != 1)
env = (Env *) allocBytes(sizeof(Env) + size * sizeof(Value *));
else {
/* see allocValue for explanations. */
if (!*env1AllocCache) {
*env1AllocCache = GC_malloc_many(sizeof(Env) + sizeof(Value *));
if (!*env1AllocCache) throw std::bad_alloc();
}
void * p = *env1AllocCache;
*env1AllocCache = GC_NEXT(p);
GC_NEXT(p) = nullptr;
env = (Env *) p;
}
env->type = Env::Plain;
/* We assume that env->values has been cleared by the allocator; maybeThunk() and lookupVar fromWith expect this. */

3
src/libexpr/eval.hh
View file

@ -136,6 +136,9 @@ private:
/* Allocation cache for GC'd Value objects. */
std::shared_ptr<void *> valueAllocCache;
/* Allocation cache for size-1 Env objects. */
std::shared_ptr<void *> env1AllocCache;
public:
EvalState(