Previously a bitmap of buffers was repeatedly scanned to see which buffers
still contain data. This process was needlessly wasting cycles (seen as a
hotspot when profiled) and worse yet, the workload increased with the number
of CPU cores (=> buffers used) to handle.
The new implementation instead maintains a list of buffer indices that have to
be handled. This list does not contain empty buffers, so each loop iteration
performs some work, instead of just spinning in search for buffers to handle.
Initializing structures for callstack processing (building memory map of the
process, gathering kernel symbols, etc) takes some time, which in some cases
may be significant.
Callstack queries are now handled on a separate thread. In such setup it no
longer makes sense to block main thread execution with this lengthy init
process.
All the heavy initialization phase has been now moved to this separate
processing thread. Some initial callstack queries may now not produce
responses as promptly as before, but this is only because the main thread is
able to start working earlier.
Some parts of the initialization process may be critical to do in the main
thread, for example because the function responsible for gathering callstacks
must be loaded first. This is done still on the main thread, in a new function
InitCallstackCritical().
Note that the negative glyph spacing is const here, regardless of the font
scaling. The alternative of using proportional spacing in reality does not
work as good as it sounds. With fractional scaling some of the glyphs will
no longer land on exact pixel boundaries, which results in blurry text.
Looking at the potential solutions for this problem is moot point, as with
the non-fractional scale of 2x and glyph spacing of -2, there is no longer
enough space separating some letters, which is especially visible in words
like "common" or register "xmm", where the "mm" pair becomes joined.
