Changeset f55d54d

Timestamp:

May 5, 2021, 12:58:55 PM (4 years ago)

Author:

Thierry Delisle <tdelisle@…>

Branches:

ADT, arm-eh, ast-experimental, enum, forall-pointer-decay, jacob/cs343-translation, master, new-ast-unique-expr, pthread-emulation, qualifiedEnum

Children:

f302d80

Parents:

d653faf

Message:

Removed call to polymorphic 'min' which caused MASSIVE slowdown.

File:

• libcfa/src/concurrency/ready_queue.cfa (modified) (2 diffs)

libcfa/src/concurrency/ready_queue.cfa

@@ -398 +398 @@
 
                 if(proc->rdq.target == -1u) {
-                        proc->rdq.target = __tls_rand() % lanes.count;
-                        unsigned it1  = proc->rdq.itr;
-                        unsigned it2  = proc->rdq.itr + 1;
-                        unsigned idx1 = proc->rdq.id + (it1 % READYQ_SHARD_FACTOR);
-                        unsigned idx2 = proc->rdq.id + (it2 % READYQ_SHARD_FACTOR);
+                        _Static_assert(READYQ_SHARD_FACTOR == 2);
+                        unsigned idx1 = proc->rdq.id + 0;
+                        unsigned idx2 = proc->rdq.id + 1;
                         unsigned long long tsc1 = ts(lanes.data[idx1]);
                         unsigned long long tsc2 = ts(lanes.data[idx2]);
-                        proc->rdq.cutoff = min(tsc1, tsc2);
-                        if(proc->rdq.cutoff == 0) proc->rdq.cutoff = -1ull;
+                        proc->rdq.target = __tls_rand() % lanes.count;
+
+                        // WARNING: std::min is polymorphic and therefore causes 500% slowdown instead of the expected 2%
+                        proc->rdq.cutoff = tsc1 < tsc2 ? tsc1 : tsc2; 
                 }
                 else {
@@ -418 +418 @@
 
                 for(READYQ_SHARD_FACTOR) {
-                        unsigned i = proc->rdq.id + (--proc->rdq.itr % READYQ_SHARD_FACTOR);
+                        unsigned i = proc->rdq.id + (proc->rdq.itr++ % READYQ_SHARD_FACTOR);
                         if($thread * t = try_pop(cltr, i __STATS(, __tls_stats()->ready.pop.local))) return t;
                 }