Hi,
JIT is typically used by server applications such as NGNIX webserver, Suricata Intrusion Detection System, ModSecurity firewall, etc. and it seems they are happy with it. Some Korean guys made a paper about integrating JIT into Snort:
http://kiise.or.kr/e_journal/2013/4/CST/pdf/01.pdf They also have the same conclusion as yours: JIT compilation has a considerable overhead, but since server applications are rarely restarted, this is not an issue. You can also use a deferred compilation in a second thread if server startup time is important (and use the interpreter if a pattern is not yet compiled).
The other typical use case is searching a single pattern in a huge input, such as GNU grep, ag (silver searcher), etc.
In short JIT only helps if you compile a pattern once, and use it several times. It is inefficient for searching a pattern once in a small string like checking a version string.
I don't understand this: "pattern is reused many times in a row in VM, without use of other
patterns between". Why other patterns can not be used?
Regards,
Zoltan
ND <nadenj@???> írta:
>>
Good day!>
>
>
As I trying to say some time ago, PCRE-JIT in most applications is >
useless. It only slowing matching process.>
>
Consider timings. In most real situations JIT compile+run time greatly >
exceeds interpreter compile+run time.>
Taking this into account there are very few circumstances when JIT brings >
benefits to user:>
- JIT compile+run time is less then interpreter run time (I think that >
number of this cases is about a zero);>
- pattern is reused many times in a row in VM, without use of other >
patterns between (IMHO number of this cases is also about a zero).>
>
So JIT without ability to use JIT-precompiled patterns have a ve-e-e-ry >
limited applicability.>
May be I'm err. Correct me please if so.>
>
I propose add to JIT ability of saving JIT-compiled data. So full >
precompiled pattern can be used by main application. This eliminates a JIT >
compile time costs and allow to use a speed benefits of JIT in most cases.>
I understand than compiled JIT-data saved on one platform probably can't >
be used on other platforms. But it can be used by application then starts >
on one platform with great effectiveness.>
>
>
I take this opportunity to thank Phillip and Zoltan for large efforts and >
great product.>
Best regards.>
>
-- >
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