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src: add a fast call for URL.revokeObjectURL #47794
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cc @anonrig since you have experience with Fast Calls and left this todo 😅 |
The results of running the benchmark in the pull req confidence improvement accuracy (*) (**) (***)
url/url-create-revoke-objecturl.js n=1000000 -3.27 % ±3.31% ±4.41% ±5.74%
Be aware that when doing many comparisons the risk of a false-positive result increases.
In this case, there are 1 comparisons, you can thus expect the following amount of false-positive results:
0.05 false positives, when considering a 5% risk acceptance (*, **, ***),
0.01 false positives, when considering a 1% risk acceptance (**, ***),
0.00 false positives, when considering a 0.1% risk acceptance (***) |
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I couldn't find why the fast path is not triggered. Maybe @joyeecheung, @devsnek or @addaleax might help?
@@ -22,6 +22,9 @@ using CFunctionCallbackWithBool = void (*)(v8::Local<v8::Object> receiver, | |||
using CFunctionCallbackWithStrings = | |||
bool (*)(v8::Local<v8::Value>, const v8::FastOneByteString& input); | |||
|
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using CFunctionCallbackWithStringsReturnVoid = | |||
void (*)(v8::Local<v8::Value>, const v8::FastOneByteString& input); |
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@joyeecheung You used Local<v8::Object>
for the receiver, whereas, in CanParse
@KhafraDev used Local<v8::Value>
for the receiver. Which one is the correct usage for the Fast API, or is both of them correct?
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The strings returned by createObjectURL()
are cons strings. They won't hit the fast API.
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Is this documented? How can we update the benchmark to flatten the string?
(For people who didn't know what cons strings
mean: cons strings are pairs of strings, result of concatenation.)
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Adding hello-1-2-3
as an input triggers fast api, but even crypto.randomUUID()
as a parameter does not trigger fast API...
function main({ n }) {
bench.start();
for (let i = 0; i < n; i += 1) {
URL.revokeObjectURL('hello-1-2-3');
}
bench.end(n);
}
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FastOneByteString
means the string type is a sequential one byte string. The string types are internal to V8 and subject to changes. I don't think it's meaningful to flatten the string in the benchmark if users in the wild are going to pass urls returned by createObjectURL()
to it...
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The JS-land version buffers the UUID so to match the performance the C++ version needs to buffer the UUID as well. Also snprintf()
can be slow if it's heavily used.
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I think doing all this would probably make the C++ side way more complicated than the original TODO intended, is there no faster way of string allocation on C++ side?
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You could also just merge the concatenation in createObjectURL()
from JS land into Blob::StoreDataObject
and concatenate the strings from C++ instead.
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The string should be created with NewFromOneByte()
, not NewFromUtf8()
as in 268fc13 because it's guaranteed to be one-byte and does not need transcoding.
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okay so i tried this
diff --git a/src/node_blob.cc b/src/node_blob.cc
index 7db8684904..45242e7c44 100644
--- a/src/node_blob.cc
+++ b/src/node_blob.cc
@@ -391,13 +391,19 @@ void Blob::StoreDataObject(const v8::FunctionCallbackInfo<v8::Value>& args) {
size_t length = args[2].As<Uint32>()->Value();
Utf8Value type(env->isolate(), args[3]);
+ std::string key_str(*key, key.length());
binding_data->store_data_object(
- std::string(*key, key.length()),
- BlobBindingData::StoredDataObject(
- BaseObjectPtr<Blob>(blob),
- length,
- std::string(*type, type.length())));
+ key_str,
+ BlobBindingData::StoredDataObject(BaseObjectPtr<Blob>(blob),
+ length,
+ std::string(*type, type.length())));
+ std::string final_url = "blob:nodedata:" + key_str;
+ args.GetReturnValue().Set(String::NewFromOneByte(env->isolate(),
+ reinterpret_cast<const uint8_t*>(final_url.data()),
+ v8::NewStringType::kNormal,
+ final_url.length())
+ .ToLocalChecked());
}
fast paths are being hit and perf is maybe little bit better than 268fc13 but on the benchmark in the commit, its still slower than the normal js version unfortunately 😓
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This is an attempt at resolving a TODO left in #47728 regarding adding a fast call for
URL.revokeObjectURL
Unfortunately it seems like either the fast call is not getting called or there is no perf benefit for doing this most probably I have made the integration wrong but I am unable to understand what may be wrong hence opening this as a draft for any help possibleThank You!
Refs: #47728