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 <nad...@mail.ru> 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.> > -- > ## List details at https://lists.exim.org/mailman/listinfo/pcre-dev > -- ## List details at https://lists.exim.org/mailman/listinfo/pcre-dev
