Performance compared to lua-cjson. #275
Comments
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Wow. This is what I have been planning to do with RapidJSON. I have just peek into the code and find out it uses I will need some time to do profiling with your performance tests. P.S. Testing performance on Travis seems not a good practice. As the loading of the server node may be changing all the time. |
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VC2013 32-bit /Ox It seems writing string in RapidJSON performance is worse than lua-cjson (e.g. |
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I reviewed the code for stringifying string. They are actually very similar. The difference is that, static void json_append_string(lua_State *l, strbuf_t *json, int lindex)
{
const char *escstr;
int i;
const char *str;
size_t len;
str = lua_tolstring(l, lindex, &len);
/* Worst case is len * 6 (all unicode escapes).
* This buffer is reused constantly for small strings
* If there are any excess pages, they won't be hit anyway.
* This gains ~5% speedup. */
strbuf_ensure_empty_length(json, len * 6 + 2);
strbuf_append_char_unsafe(json, '\"');
for (i = 0; i < len; i++) {
escstr = char2escape[(unsigned char)str[i]];
if (escstr)
strbuf_append_string(json, escstr);
else
strbuf_append_char_unsafe(json, str[i]);
}
strbuf_append_char_unsafe(json, '\"');
}After trying to do the same logic in RapidJSON (just hacking, not fully implemented for all streams, and drop transcoding functionality), it gains some improvements but still worse than cjson: |
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That nice improvement.
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Today I learnt about Just changing one line of code in template<typename T>
RAPIDJSON_FORCEINLINE T* Push(size_t count = 1) {
// Expand the stack if needed
if (RAPIDJSON_UNLIKELY(stackTop_ + sizeof(T) * count >= stackEnd_))
Expand<T>(count);
T* ret = reinterpret_cast<T*>(stackTop_);
stackTop_ += sizeof(T) * count;
return ret;
}The performance boosts for both parsing, and stringifying to StringBuffer, as they both uses This technique shall be applied to string encoding/decoding also. |
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Sounds like a good idea. 👍 |
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I try to rerun the benchmark on OS X: After properly build in release configuration: Enable The most obvious improvement is |
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#544 Optimized Before: After Among above, the affected tests are:
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rerun the lua performance test, showing the same kind of improvements: |
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@miloyip |
I have write a json module for lua based on RapidJSON.
The performance test result over lua-cjson is:
On windows:
My json module performance a bit slower than cjson when processing booleans nulls strings. but much faster than cjson when processing numbers.
I guess is because the MSVC is slow when convert numbers <--> string.
On Linux (tested on Travis):
My json module only a bit faster when encoding numbers.
My question is:
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