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ZMQII-56: Avoid allocation of chunk in yqueue.hpp by keeping a spare one

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This commit is contained in:
Martin Sustrik 2010-02-03 20:04:44 +01:00
parent 72bbc92b70
commit 0f697fe2b4
2 changed files with 27 additions and 5 deletions
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1
AUTHORS
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@ -11,6 +11,7 @@ Erich Heine
Erik Rigtorp
Frank Denis
George Neill
Joe Thornber
Jon Dyte
Kamil Shakirov
Martin Hurton

31
src/yqueue.hpp
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@ -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&);