Changeset 0fb3ee5 for libcfa

Timestamp:

Jan 17, 2022, 7:47:29 PM (4 years ago)

Author:

Thierry Delisle <tdelisle@…>

Branches:

ADT, ast-experimental, enum, forall-pointer-decay, master, pthread-emulation, qualifiedEnum

Children:

f55f110

Parents:

25337e0

Message:

@optim: maximize chances "cache" array stays in cache.

Location:

libcfa/src/concurrency

Files:

• kernel.hfa (modified) (2 diffs)
• ready_queue.cfa (modified) (1 diff)

libcfa/src/concurrency/kernel.hfa

@@ -68 +68 @@
                 unsigned last;
                 signed   cpu;
-                // unsigned long long int cutoff;
         } rdq;
 
@@ -154 +153 @@
 };
 
-struct __attribute__((aligned(128))) __cache_id_t {
+struct __attribute__((aligned(16))) __cache_id_t {
         volatile unsigned id;
 };

libcfa/src/concurrency/ready_queue.cfa

@@ -399 +399 @@
                 /* paranoid */ verify(cpu < cpu_info.hthrd_count);
                 unsigned this_cache = cpu_info.llc_map[cpu].cache;
-                __atomic_store_n(&lanes.caches[this / READYQ_SHARD_FACTOR].id, this_cache, __ATOMIC_RELAXED);
+
+                // Super important: don't write the same value over and over again
+                // We want to maximise our chances that his particular values stays in cache
+                if(lanes.caches[this / READYQ_SHARD_FACTOR].id != this_cache)
+                        __atomic_store_n(&lanes.caches[this / READYQ_SHARD_FACTOR].id, this_cache, __ATOMIC_RELAXED);
 
                 const unsigned long long ctsc = rdtscl();