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feat(3p/nix): Statically pass bindings capacity where possible

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To aid in making the decision of where to (currently just statically)
use a vector or btree as the backing implementation, add an extra
constructor argument to Bindings::NewGC for a capacity, and use
a (currently hardcoded at 32, for no good reason other than it felt like
a reasonable number) pivot to switch between our possible backing
implementations. Then, update all the call sites where it feels
reasonable that we know the capacity statically to *pass* that capacity
to the constructor.

Paired-With: Luke Granger-Brown <git@lukegb.com>
Paired-With: Vincent Ambo <mail@tazj.in>
Paired-With: Perry Lorier <isomer@tvl.fyi>
Change-Id: I1858c161301a1cd0e83aeeb9a58839378869e71d
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1124
Tested-by: BuildkiteCI
Reviewed-by: lukegb <lukegb@tvl.fyi>
Reviewed-by: isomer <isomer@tvl.fyi>
This commit is contained in:
Griffin Smith 2020-07-12 17:29:45 -04:00 • committed by glittershark
parent d5505fcff9
commit d5597b4784
5 changed files with 39 additions and 31 deletions
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56
third_party/nix/src/libexpr/attr-set.cc vendored
View file

@ -11,6 +11,8 @@
namespace nix {
constexpr size_t ATTRS_CAPACITY_PIVOT = 32;
BindingsIterator& BindingsIterator::operator++() {
std::visit(util::overloaded{
[](AttributeMap::iterator& iter) { ++iter; },
@ -132,27 +134,13 @@ void BTreeBindings::merge(Bindings& other) {
}
}
void EvalState::mkAttrs(Value& v, size_t capacity) {
clearValue(v);
v.type = tAttrs;
v.attrs = Bindings::NewGC();
assert(v.attrs->begin() == v.attrs->begin());
assert(v.attrs->end() == v.attrs->end());
nrAttrsets++;
nrAttrsInAttrsets += capacity;
}
/* Create a new attribute named 'name' on an existing attribute set stored
in 'vAttrs' and return the newly allocated Value which is associated with
this attribute. */
Value* EvalState::allocAttr(Value& vAttrs, const Symbol& name) {
Value* v = allocValue();
vAttrs.attrs->push_back(Attr(name, v));
return v;
}
class VectorBindings : public Bindings {
public:
VectorBindings() {};
VectorBindings(size_t capacity) : attributes_() {
attributes_.reserve(capacity);
};
size_t size() override;
bool empty() override;
void push_back(const Attr& attr) override;
@ -246,8 +234,32 @@ Bindings::iterator VectorBindings::end() {
return BindingsIterator{attributes_.end()};
}
// TODO pick what to do based on size
Bindings* Bindings::NewGC() { return new (GC) BTreeBindings; }
// Bindings* Bindings::NewGC() { return new (GC) VectorBindings; }
Bindings* Bindings::NewGC(size_t capacity) {
if (capacity > ATTRS_CAPACITY_PIVOT) {
return new (GC) BTreeBindings;
} else {
return new (GC) VectorBindings(capacity);
}
}
void EvalState::mkAttrs(Value& v, size_t capacity) {
clearValue(v);
v.type = tAttrs;
v.attrs = Bindings::NewGC(capacity);
assert(v.attrs->begin() == v.attrs->begin());
assert(v.attrs->end() == v.attrs->end());
nrAttrsets++;
nrAttrsInAttrsets += capacity;
}
/* Create a new attribute named 'name' on an existing attribute set stored
in 'vAttrs' and return the newly allocated Value which is associated with
this attribute. */
Value* EvalState::allocAttr(Value& vAttrs, const Symbol& name) {
Value* v = allocValue();
vAttrs.attrs->push_back(Attr(name, v));
return v;
}
} // namespace nix