scott.smith added a comment.
I can make more measurements on this.
================
Comment at: source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp:1994
- TaskRunner<uint32_t> task_runner;
- for (uint32_t cu_idx = 0; cu_idx < num_compile_units; ++cu_idx)
- task_runner.AddTask(parser_fn, cu_idx);
-
- while (true) {
- std::future<uint32_t> f = task_runner.WaitForNextCompletedTask();
- if (!f.valid())
- break;
- uint32_t cu_idx = f.get();
+ TaskMap(num_compile_units, 1, parser_fn);
----------------
clayborg wrote:
> Note that we lost performance here. The old code would run:
>
> ```
> while (true) {
> std::future<uint32_t> f = task_runner.WaitForNextCompletedTask();
> // Do expensive work as soon as possible with any random task that
> completes as soon as it completes.
> ```
>
> Your current code says "wait to do all expensive work until I complete
> everything and then do all of the expensive work".
>
>
>
>
The following loop is not expensive, it's simple vector concatenation of fairly
simple types. The actual slow work is Finalize(), which calls Sort().
m_function_basename_index is of type NameDIE, which has a UniqueCStringMap
member, which declared collection as std::vector.
Though arguably the Append should be pushed down into the RunTasks below.
================
Comment at: source/Utility/TaskPool.cpp:100
+ for (size_t i = 0; i < est_batches; i++)
+ futures[i].wait();
+}
----------------
clayborg wrote:
> TaskRunner is smart in the way it runs things: it lets you run N things and
> get each item as it completes. This implementation, if read it correctly,
> will serialize everything. So if you have 100 items to do and item at index 0
> takes 200 seconds to complete, and items 1 - 99 take 1ms to complete, you
> will need to wait for task 0 to complete before you can start parsing the
> data. This will slow down the DWARF parser if you switch over to this.
If items 1-99 complete quickly, there isn't much advantage to handling their
output before handling the output of item 0, since item 0 is likely to produce
more output than 1-99 combined.
Repository:
rL LLVM
https://reviews.llvm.org/D32757
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