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-rw-r--r--src/yqueue.hpp31
1 files changed, 26 insertions, 5 deletions
diff --git a/src/yqueue.hpp b/src/yqueue.hpp
index 45b2b18..cb20697 100644
--- a/src/yqueue.hpp
+++ b/src/yqueue.hpp
@@ -24,6 +24,7 @@
#include <stddef.h>
#include "err.hpp"
+#include "atomic_ptr.hpp"
namespace zmq
{
@@ -37,9 +38,9 @@ namespace zmq
// pop on the empty queue and that both threads don't access the same
// element in unsynchronised manner.
//
- // T is the type of the object in the queue
+ // T is the type of the object in the queue.
// N is granularity of the queue (how many pushes have to be done till
- // actual memory allocation is required)
+ // actual memory allocation is required).
template <typename T, int N> class yqueue_t
{
@@ -69,6 +70,10 @@ namespace zmq
begin_chunk = begin_chunk->next;
delete o;
}
+
+ chunk_t *sc = spare_chunk.xchg (NULL);
+ if (sc)
+ delete sc;
}
// Returns reference to the front element of the queue.
@@ -94,8 +99,13 @@ namespace zmq
if (++end_pos != N)
return;
- end_chunk->next = new (std::nothrow) chunk_t;
- zmq_assert (end_chunk->next);
+ chunk_t *sc = spare_chunk.xchg (NULL);
+ if (sc) {
+ end_chunk->next = sc;
+ } else {
+ end_chunk->next = new (std::nothrow) chunk_t;
+ zmq_assert (end_chunk->next);
+ }
end_chunk = end_chunk->next;
end_pos = 0;
}
@@ -107,7 +117,13 @@ namespace zmq
chunk_t *o = begin_chunk;
begin_chunk = begin_chunk->next;
begin_pos = 0;
- delete o;
+
+ // 'o' has been more recently used than spare_chunk,
+ // so for cache reasons we'll get rid of the spare and
+ // use 'o' as the spare.
+ chunk_t *cs = spare_chunk.xchg (o);
+ if (cs)
+ delete cs;
}
}
@@ -131,6 +147,11 @@ namespace zmq
chunk_t *end_chunk;
int end_pos;
+ // People are likely to produce and consume at similar rates. In
+ // this scenario holding onto the most recently freed chunk saves
+ // us from having to call new/delete.
+ atomic_ptr_t<chunk_t> spare_chunk;
+
// Disable copying of yqueue.
yqueue_t (const yqueue_t&);
void operator = (const yqueue_t&);