original-brownbear commented on code in PR #13472:
URL: https://github.com/apache/lucene/pull/13472#discussion_r1642938462
##########
lucene/core/src/java/org/apache/lucene/search/TaskExecutor.java:
##########
@@ -144,32 +128,45 @@ public boolean cancel(boolean mayInterruptIfRunning) {
}
List<T> invokeAll(Executor executor) throws IOException {
- boolean runOnCallerThread = numberOfRunningTasksInCurrentThread.get() >
0;
- for (Runnable runnable : futures) {
- if (runOnCallerThread) {
- runnable.run();
- } else {
- executor.execute(runnable);
+ final int count = futures.size();
+ // taskId provides the first index of an un-executed task in #futures
+ final AtomicInteger taskId = new AtomicInteger(0);
+ // we fork execution count - 1 tasks to execute at least one task on the
current thread to
+ // minimize needless forking and blocking of the current thread
+ if (count > 1) {
+ final Runnable work =
+ () -> {
+ int id = taskId.getAndIncrement();
+ if (id < count) {
+ futures.get(id).run();
+ }
+ };
+ for (int j = 0; j < count - 1; j++) {
+ executor.execute(work);
+ }
+ }
+ // try to execute as many tasks as possible on the current thread to
minimize context
+ // switching in case of long running concurrent
+ // tasks as well as dead-locking if the current thread is part of
#executor for executors that
+ // have limited or no parallelism
+ int id;
+ while ((id = taskId.getAndIncrement()) < count) {
+ futures.get(id).run();
+ if (id >= count - 1) {
+ // save redundant CAS in case this was the last task
+ break;
}
}
Throwable exc = null;
- List<T> results = new ArrayList<>(futures.size());
- for (Future<T> future : futures) {
+ List<T> results = new ArrayList<>(count);
+ for (int i = 0; i < count; i++) {
Review Comment:
I think it's the same order before and after. I can back out this change, I
just wanted to remove the allocation of the iterator I believe. I had a branch
with some more changes that help this behave better cache/memory wise and cut
this one out of it. Maybe a little beyond the main mission of the change :) I
can back this change out if you want? :)
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