Bullet Physics - btHashMap performance in collision filter callback

Question

The built-in collision filter groups and masks are not enough to store the information needed by my collision filter callback.

I have to use a hash table to store my collision data, and the btHashMap, wich is also included in the library seems the way to go, because of the SIMD code optimizations.

Inspecting the source code I've found that searching for an element in a btHashMap depends on the number of stored elements, so it is not really O(1) but O(n).

Value*  find(const Key& key)
{
    int index = findIndex(key);
    if (index == BT_HASH_NULL)
    {
        return NULL;
    }
    return &m_valueArray[index];
}


int findIndex(const Key& key) const
{
    unsigned int hash = key.getHash() & (m_valueArray.capacity()-1);

    if (hash >= (unsigned int)m_hashTable.size())
    {
        return BT_HASH_NULL;
    }

    int index = m_hashTable[hash];
    while ((index != BT_HASH_NULL) && key.equals(m_keyArray[index]) == false)
    {
        index = m_next[index];
    }
    return index;
}

Although the table will be storing no more than 10 elements, would it be a performance hit to use btHashMap in that way?