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Increase size of zmq_msg_t to 64 bytes

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Increasing it would have at least two benefits -

* More messages would be 'VSM' messages, so it would reduce allocation
overhead a bit.
* Remove any chance of false sharing of things that are, by design,
pushed by value onto a ypipe_t<msg_t> which is shared between two threads.

The only downside I see is slightly increased memory consumption on memory
constrained applications.

- Full discussion of this rationale is part of issue #1295
This commit is contained in:
Thomas Rodgers
2015-01-10 16:44:55 -06:00
parent a55005feb1
commit 90194036bf
2 changed files with 2 additions and 2 deletions
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2
include/zmq.h
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@@ -195,7 +195,7 @@ ZMQ_EXPORT int zmq_ctx_destroy (void *context);
/* 0MQ message definition. */ /* 0MQ message definition. */
/******************************************************************************/ /******************************************************************************/
typedef struct zmq_msg_t {unsigned char _ [48];} zmq_msg_t; typedef struct zmq_msg_t {unsigned char _ [64];} zmq_msg_t;
typedef void (zmq_free_fn) (void *data, void *hint); typedef void (zmq_free_fn) (void *data, void *hint);

2
src/msg.hpp
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@@ -92,7 +92,7 @@ namespace zmq
// Size in bytes of the largest message that is still copied around // Size in bytes of the largest message that is still copied around
// rather than being reference-counted. // rather than being reference-counted.
enum { msg_t_size = 48 }; enum { msg_t_size = 64 };
enum { max_vsm_size = msg_t_size - (8 + sizeof (metadata_t *) + 3) }; enum { max_vsm_size = msg_t_size - (8 + sizeof (metadata_t *) + 3) };
// Shared message buffer. Message data are either allocated in one // Shared message buffer. Message data are either allocated in one