TrieCache: Fine tune the size of the local and node cache (#14191) (paritytech#37)

First, we increase the size to 10MiB for the local cache. Second, we give the node cache a bigger
max size than the value cache, see the changed comment on why.

In general this should ensure that we are able to cache the `:code` and not directly throw it out of
the cache because it is too big (which currently happens when the size of the runtime > 2MiB). In
the future this should be improved to ensure that certain values are not removed from the cache at
all, like `:code`.

Co-authored-by: Bastian Köcher <git@kchr.de>
Signed-off-by: Robert G. Jakabosky <rjakabosky+neopallium@neoawareness.com>

Author: Neopallium

substrate/primitives/trie/src/cache/mod.rs

@@ -91,9 +91,13 @@ const LOCAL_NODE_CACHE_MAX_INLINE_SIZE: usize = 512 * 1024;
 const LOCAL_VALUE_CACHE_MAX_INLINE_SIZE: usize = 512 * 1024;
 
 /// The maximum size of the memory allocated on the heap by the local cache, in bytes.
-const LOCAL_NODE_CACHE_MAX_HEAP_SIZE: usize = 2 * 1024 * 1024;
+///
+/// The size of the node cache should always be bigger than the value cache. The value
+/// cache is only holding weak references to the actual values found in the nodes and
+/// we account for the size of the node as part of the node cache.
+const LOCAL_NODE_CACHE_MAX_HEAP_SIZE: usize = 8 * 1024 * 1024;
 /// Same as [`LOCAL_NODE_CACHE_MAX_HEAP_SIZE`].
-const LOCAL_VALUE_CACHE_MAX_HEAP_SIZE: usize = 4 * 1024 * 1024;
+const LOCAL_VALUE_CACHE_MAX_HEAP_SIZE: usize = 2 * 1024 * 1024;
 
 /// The size of the shared cache.
 #[derive(Debug, Clone, Copy)]