Commit c2268466 authored by Simon Marlow's avatar Simon Marlow
Browse files

scheduleProcessInbox: use non-blocking acquire, and take the whole queue

This is an improvement from my GC branch, that helps performance for
intensive message-passing communication between Capabilities.
parent 26f4bfc8
......@@ -951,14 +951,38 @@ static void
scheduleProcessInbox (Capability *cap USED_IF_THREADS)
#if defined(THREADED_RTS)
Message *m;
Message *m, *next;
int r;
while (!emptyInbox(cap)) {
if (cap->r.rCurrentNursery->link == NULL ||
g0->n_new_large_words >= large_alloc_lim) {
scheduleDoGC(cap, cap->running_task, rtsFalse);
// don't use a blocking acquire; if the lock is held by
// another thread then just carry on. This seems to avoid
// getting stuck in a message ping-pong situation with other
// processors. We'll check the inbox again later anyway.
// We should really use a more efficient queue data structure
// here. The trickiness is that we must ensure a Capability
// never goes idle if the inbox is non-empty, which is why we
// use cap->lock (cap->lock is released as the last thing
// before going idle; see Capability.c:releaseCapability()).
r = TRY_ACQUIRE_LOCK(&cap->lock);
if (r != 0) return;
m = cap->inbox;
cap->inbox = m->link;
cap->inbox = (Message*)END_TSO_QUEUE;
executeMessage(cap, (Message *)m);
while (m != (Message*)END_TSO_QUEUE) {
next = m->link;
executeMessage(cap, m);
m = next;
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