[lldb] Rate limit progress reports -- different approach [WIP-ish]

Have the Progress class spawn a thread to periodically send progress
reports.

The reporting period could be made configurable, but for now I've
hardcoded it to 100ms. (This is the main WIP part)

It could be argued that creating a thread for progress reporting adds
overhead, but I would counter that by saying "If the task is so fast
that creating a thread noticably slows it down, then it really doesn't
need progress reporting".

For me, this speeds up DWARF indexing by about 1.5% (which is only
slightly above the error bars), but I expect it will have a much bigger
impact in situations where printing a single progress update takes a
nontrivial amount of time.

Differential Revision: https://reviews.llvm.org/D152364

0 files changed, 0 insertions, 0 deletions