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LibJS: Use entire array of SimpleIndexedPropertyStorage before growing

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A common use case in JS is pushing items in an array in a loop.
A simple test case of 100_000 pushes took around ~20 seconds.
This is due to the fact that any pushed element per definition is beyond
the current size of the array. This meant calling grow_storage_if_needed
which then grew the storage by 25%. But this was done on every single
push, growing the array just a little bigger than its current capacity.

Now we now first use capacity of the array and only grow if the array
is actually full.
This decreases the time for 100_000 to around 0.35 seconds.
One problem is that we never shrink the capacity of the array but this
was already an issue before this.
This commit is contained in:
davidot 2022-02-12 23:44:58 +01:00 • committed by Linus Groh
parent 24d5ca4a9d
commit eac3c4c127
1 changed files with 8 additions and 3 deletions
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11
Userland/Libraries/LibJS/Runtime/IndexedProperties.cpp
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@ -35,8 +35,13 @@ void SimpleIndexedPropertyStorage::grow_storage_if_needed()
{ {
if (m_array_size <= m_packed_elements.size()) if (m_array_size <= m_packed_elements.size())
return; return;
// Grow storage by 25% at a time.
m_packed_elements.resize(m_array_size + (m_array_size / 4)); if (m_array_size <= m_packed_elements.capacity()) {
m_packed_elements.resize_and_keep_capacity(m_array_size);
} else {
// When the array is actually full grow storage by 25% at a time.
m_packed_elements.resize_and_keep_capacity(m_array_size + (m_array_size / 4));
}
} }
void SimpleIndexedPropertyStorage::put(u32 index, Value value, PropertyAttributes attributes) void SimpleIndexedPropertyStorage::put(u32 index, Value value, PropertyAttributes attributes)
@ -73,7 +78,7 @@ ValueAndAttributes SimpleIndexedPropertyStorage::take_last()
bool SimpleIndexedPropertyStorage::set_array_like_size(size_t new_size) bool SimpleIndexedPropertyStorage::set_array_like_size(size_t new_size)
{ {
m_array_size = new_size; m_array_size = new_size;
m_packed_elements.resize(new_size); m_packed_elements.resize_and_keep_capacity(new_size);
return true; return true;
} }