If you embed V8 yourself, the runtime flags --regexp-tier-up and
--regexp-tier-up-ticks
<https://cs.chromium.org/chromium/src/v8/src/flags/flag-definitions.h?l=1267&rcl=be638514c9876e80c222068059b205d64091c78d>
control
tier-up behavior.
Do you have an example of a particularly slow regexp pattern and subject
string?
On Thu, Oct 24, 2019 at 10:14 PM Joel Scarfone <joelrscarf...@gmail.com>
wrote:
> Let's say I have a Script that uses somewhere in the realm 100 regex's in
> different functions. I want the first call to each of those functions to be
> fast, so I move the constructor to the global object to pre-compile the
> regex's. From the v8 docs, "In its default configuration, V8 compiles
> regular expressions to native code upon the first execution", so I force
> this pre-complication with something like `for(var rule of regexRules) {
> "".match(regex) } `. Doing this, I notice a significant improvement in the
> execution on first call back into the context to execute a function that
> uses these regex's.
>
> Is there a way to change this default configuration?
>
> Joel
>
> On Thursday, 24 October 2019 01:12:54 UTC-4, Jakob Gruber wrote:
>>
>>
>>
>> On Wed, Oct 23, 2019 at 5:12 PM Joel Scarfone <joelrs...@gmail.com>
>> wrote:
>>
>>> Hi!
>>>
>>> I'm looking for details on how v8's regular expression optimizations
>>> work under the covers, and if there might be something to improve the
>>> performance of a given regular expressions first execution. From what it
>>> looks like trying some things out, v8 does most of it's optimizations after
>>> a call that uses the RegExp and not when the constructor is called (eg.
>>> through `new RegExp()`).
>>>
>>
>> I'm not aware of much documentation on this topic. A recent blog post (
>> https://v8.dev/blog/regexp-tier-up) discusses the recent addition of
>> tiering and describes performance work on the interpreter. But for details
>> you'll have to dig through the source code.
>>
>> As you say, a regexp is compiled lazily at the first exec call. With
>> tiering, we first compile to bytecode, then later recompile to native code.
>> There are many intricacies involved, e.g. we cache compilation artifacts
>> keyed on {pattern,flags}, and constructing a regexp instance is expected to
>> be cheaper from a literal (/abc/) than when using the constructor (new
>> RegExp("abc", "")).
>>
>>
>>>
>>> I am Wondering what some options are in this area to move around the
>>> cost of compiling/running the regular expression.
>>>
>>
>> I think I'd need more details on what you want to achieve to give a
>> meaningful answer.
>>
>>
>>>
>>> Thanks in advance!
>>>
>>> Joel
>>>
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