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From "Vladimir Beliaev" <vladimir.k.beli...@gmail.com>
Subject Re: [drlvm] verifier discussion
Date Fri, 06 Jul 2007 13:05:39 GMT
I'm ok with opportunity to pick 1 of 2 verifiers on a build time... The rest
of points seems to be resonable for me.

Thanks
Vladimir Beliaev

2007/7/6, Mikhail Loenko <mloenko@gmail.com>:
>
> Thank you all for your comments!
>
> Here I combined my responses to all the comments.
>
> Java6 verification can be obtained from both implementations basically
> by removing the code :). Since legacy apps will exist some (I guess
> long) time, we will need pre- Java 6 verifier, so working on its
> quality and performance makes sense IMHO.
>
> I don't think that time and efforts are an issue. The time flies when
> you are having fun :) I'm volunteering to do all the necessary
> updates.
>
> I tested the patch on most of the scenarios that are in BTI2,
> including TPTP tests, so I don't expect significant problems here, and
> sure we may want to decide to switch back later like we did it with
> our first attempt to switch to GCv5.
>
> As for moving this functionality to dll, I'm not sure it's the right
> thing to do. We had several examples in Harmony when we had
> alternative implementations of the same thing. In most of the cases
> (e.g. Crypto, Math, RMI) we had a build switch, and only in case of GC
> we had a runtime switch.
>
> GC is special because it was easy to identify where the bug is by
> switching GC in runtime. Since almost all the verifier bugs can be
> easily identified by "VerifyError" or by using "-noverify" option, I
> think a build switch is enough here.
>
> The SPECs do not spend much time in verification, but I observe
> Eclipse start time improvement on my laptop.
>
> Please let me know if it sounds reasonable
>
> Thanks,
> Mikhail
>
> 2007/7/5, Xiao-Feng Li <xiaofeng.li@gmail.com>:
> > It's a wise choice for Java6 to decouple the type inferencing from
> > online type checking. To decide which verifier to use, we probably
> > need know which design is better for the type checking transition.
> >
> > Thanks,
> > xiaofeng
> >
> > On 7/5/07, Alexei Fedotov <alexei.fedotov@gmail.com> wrote:
> > > Mikhail,
> > >
> > > Your verifier implemented very interesting algorithm.
> > >
> > > * We already started moving into Java 6.0 direction, and Java 6.0
> > > suggested a different verification scheme [1]. I see implementing this
> > > scheme as more important task than switching between two old
> > > verifiers.
> > >
> > > * When a new scheme is implemented the legacy scheme won't be used
> > > often, this means performance considerations are of less importance
> > > compared to minimal risk considerations and ease of bug fixing. Any
> > > switching comes at the cost of risk and increase in maintenance
> > > efforts.
> > >
> > > * The legacy scheme is to be completely removed from specification
> > > soon, so the new verifier should be separate from the old code. I
> > > found it more productive to decide which verifier code base should be
> > > a base for new development.
> > >
> > > What do you think?
> > >
> > > [1] New Java SE 6 Feature: Type Checking Verifier,
> > > https://jdk.dev.java.net/verifier.html
> > >
> > >
> > > On 7/5/07, Mikhail Loenko <mloenko@gmail.com> wrote:
> > > > We have passed code and feature freeze recently and have a momentum
> for
> > > > bigger changes in the code.
> > > >
> > > > We have recently accepted [1] a contribution of an alternative
> implementation of
> > > > bytecode verifier [2]
> > > >
> > > > New implementation demonstrated pretty nice testing [3] and
> > > > performance results [4].
> > > >
> > > > Though many bugs in current implementation were fixed and it now
> also
> > > > demonstrate good testing results, the performance difference remains
> the same.
> > > >
> > > > I suggest that we switch default implementation for Harmony
> > > >
> > > > Thanks,
> > > > Mikhail
> > > >
> > > > [1]
> http://mail-archives.apache.org/mod_mbox/harmony-dev/200706.mbox/%3c906dd82e0706040145o1173ce6dqcc671777c5b413c6@mail.gmail.com%3e
> > > >
> > > > [2] http://issues.apache.org/jira/browse/HARMONY-3363
> > > >
> > > > [3]
> http://mail-archives.apache.org/mod_mbox/harmony-dev/200703.mbox/%3c8E389A5F2FEABA4CB1DEC35A25CB39CEB48212@mssmsx411%3e
> > > >
> > > > [4]
> http://mail-archives.apache.org/mod_mbox/harmony-dev/200703.mbox/%3c906dd82e0703152337n133fafd8t8275ed9277c00204@mail.gmail.com%3e
> > > >
> > >
> > >
> > > --
> > > With best regards,
> > > Alexei,
> > > ESSD, Intel
> > >
> >
> >
> > --
> > http://xiao-feng.blogspot.com
>

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