Json string are usually created and freed immediately. Thus, there
should not be any downside in creating a larger buffer initially to
avoid the cost of moving strings around in memory due to realloc()
call.
The following script is used as benchmark to measure number of
bytes reallocated:
ovs-vsctl add-br br0
for i in `seq 0 100`; do
ovs-vsctl add-port br0 p$i
done
ovs-vsctl del-br br0
'ds_bytes_relocated' coverage counter shows that the bytes relocated
are 2.5Mbytes/sec and 17Kbytes/sec, before and after this patch applied,
respectively.
Signed-off-by: Andy Zhou <az...@nicira.com>
---
lib/json.c | 2 +-
lib/json.h | 10 ++++++++--
lib/jsonrpc.c | 6 ++++--
3 files changed, 13 insertions(+), 5 deletions(-)
diff --git a/lib/json.c b/lib/json.c
index dd85213..be76810 100644
--- a/lib/json.c
+++ b/lib/json.c
@@ -1462,7 +1462,7 @@ json_to_string(const struct json *json, int flags)
{
struct ds ds;
- ds_init(&ds);
+ json_ds_init(&ds);
json_to_ds(json, flags, &ds);
return ds_steal_cstr(&ds);
}
diff --git a/lib/json.h b/lib/json.h
index 3497035..c6b4ff5 100644
--- a/lib/json.h
+++ b/lib/json.h
@@ -30,14 +30,13 @@
* "should" be unique).
*/
+#include "dynamic-string.h"
#include "shash.h"
#ifdef __cplusplus
extern "C" {
#endif
-struct ds;
-
/* Type of a JSON value. */
enum json_type {
JSON_NULL, /* null */
@@ -127,6 +126,13 @@ enum {
};
char *json_to_string(const struct json *, int flags);
void json_to_ds(const struct json *, int flags, struct ds *);
+/* Initialize 'ds', with reserved size suitable for typical Json objects */
+static inline void
+json_ds_init(struct ds *ds)
+{
+ ds_init(ds);
+ ds_reserve(ds, 32 * 1024); /* pre allocate 32Kbytes buffer */
+}
/* JSON string formatting operations. */
diff --git a/lib/jsonrpc.c b/lib/jsonrpc.c
index b482777..81b173f 100644
--- a/lib/jsonrpc.c
+++ b/lib/jsonrpc.c
@@ -198,7 +198,8 @@ jsonrpc_log_msg(const struct jsonrpc *rpc, const char
*title,
const struct jsonrpc_msg *msg)
{
if (VLOG_IS_DBG_ENABLED()) {
- struct ds s = DS_EMPTY_INITIALIZER;
+ struct ds s;
+ json_ds_init(&s);
if (msg->method) {
ds_put_format(&s, ", method=\"%s\"", msg->method);
}
@@ -238,7 +239,7 @@ jsonrpc_send(struct jsonrpc *rpc, struct jsonrpc_msg *msg)
{
struct ofpbuf *buf;
struct json *json;
- struct ds ds = DS_EMPTY_INITIALIZER;
+ struct ds ds;
size_t length;
if (rpc->status) {
@@ -246,6 +247,7 @@ jsonrpc_send(struct jsonrpc *rpc, struct jsonrpc_msg *msg)
return rpc->status;
}
+ json_ds_init(&ds);
jsonrpc_log_msg(rpc, "send", msg);
json = jsonrpc_msg_to_json(msg);
--
1.9.1
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