gvarianttype: Garbage Collect GVariantTypeInfo
The goal of this change is to avoid re-parsing GVariantTypeInfo
on
every creation or parsing of a GVariant
byte-buffer. Parsing presents
a non-trivial amount of overhead which can typically be elided.
It was discovered that many applications and tooling are re-generating this information upon receiving a D-Bus message as they tend to process messages serially, thus dropping the last reference count.
Previously, when the last reference count for a GVariantTypeInfo
was
dropped we would finalize the parsed type information.
This change keeps GVariantTypeInfo
alive in a Garbage Collected array.
The array is collected upon reaching a 32 entries. The number 32 was
chosen because it is larger than what I've seen active on various D-Bus
based applications-or-daemons.
Take a simple test case of using GVariantBuilder
in a loop with a
debugoptimized build of GLib. A reduction in wallclock time can be
observed in the 35% to more than 70% based on the complexity of the
GVariant being created.
For cases like ibus-daemon, it was previously parsing GVariantTypeInfo
up to dozens of times per key-press/release cycle.
Closes: #3472 (closed)