mwrap_core: document the reason for padding the mutex

While 64 has an obvious meaning to me, I reject Moore's law
and have no idea what cache line sizes modern CPUs use.

1 files changed, 1 insertions, 1 deletions

diff --git a/mwrap_core.h b/mwrap_core.h
index 09b579d..94a6af3 100644
--- a/mwrap_core.h
+++ b/mwrap_core.h
@@ -68,7 +68,7 @@ static size_t *root_locating; /* determines if PL_curcop is our thread */
 static struct cds_lfht *totals;
 union padded_mutex {
         pthread_mutex_t mtx;
-        char pad[64];
+        char pad[64]; /* cache alignment for common CPUs */
 };
 
 /* a round-robin pool of mutexes */