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Merge pull request #5865 from pennae/memory-friendliness

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be more memory friendly
This commit is contained in:
Eelco Dolstra 2022-03-11 11:52:39 +01:00 • committed by GitHub
commit 31a392dfe2
7 changed files with 107 additions and 69 deletions
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38
src/libexpr/eval.cc
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@ -449,8 +449,10 @@ 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)
@ -876,42 +878,6 @@ inline Value * EvalState::lookupVar(Env * env, const ExprVar & var, bool noEval)
}
Value * EvalState::allocValue()
{
/* We use the boehm batch allocator to speed up allocations of Values (of which there are many).
GC_malloc_many returns a linked list of objects of the given size, where the first word
of each object is also the pointer to the next object in the list. This also means that we
have to explicitly clear the first word of every object we take. */
if (!*valueAllocCache) {
*valueAllocCache = GC_malloc_many(sizeof(Value));
if (!*valueAllocCache) throw std::bad_alloc();
}
/* GC_NEXT is a convenience macro for accessing the first word of an object.
Take the first list item, advance the list to the next item, and clear the next pointer. */
void * p = *valueAllocCache;
GC_PTR_STORE_AND_DIRTY(&*valueAllocCache, GC_NEXT(p));
GC_NEXT(p) = nullptr;
nrValues++;
auto v = (Value *) p;
return v;
}
Env & EvalState::allocEnv(size_t size)
{
nrEnvs++;
nrValuesInEnvs += size;
Env * env = (Env *) allocBytes(sizeof(Env) + size * sizeof(Value *));
env->type = Env::Plain;
/* We assume that env->values has been cleared by the allocator; maybeThunk() and lookupVar fromWith expect this. */
return *env;
}
void EvalState::mkList(Value & v, size_t size)
{
v.mkList(size);