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Re: [equinox-dev] Huge performance loss between Kepler and Luna/Mars on first start

> From: Tom Schindl <tom.schindl@xxxxxxxxxxxxxxx>

> Hi,
> I've been with a customer today who wants to update from Eclipse 3.x
> Kepler to the 4.x code base and so he naturally inherits the latest
> Equinox implementation who has changed in between those releases.
> The intial boot time increased from about 2 seconds to ~20 seconds on
> Mars (on Luna Equinox or better said Felix-Resolver crashes).

I think the crash may be fixed in Luna SR2, at least the version of the felix resolver was updated in both SR2 and Mars.
From a cached restart I assume you do not see this slow start.

> We profiled the bootstrap process and the whole time (95%) is eaten up
> the by felix resolver ResolverImpl#mergeCandidatePackages
> Looking at tbe hot methods we see:
> * 15% of the time is spend in ArrayList.contains()
> * 30% of the time in HashMap.getNode()
>   - called from ResolverImpl#mergeCanidatePackages 7%
>   - called from ResolverImpl#calculateExportedPackages 5%
>   - called from ResolverImpl#mergeUses 5%
> Looking Allocation counts we see the biggest amount (1.9GB) being caused
> by ArrayList.grow where we could track back 1.84GB to
> mergeCandidatePackages once more which suggests that the initial sizes
> choosen for the arrays there are probably not optimal.
> One very interesting to this piece of software is that it uses:
> a) only require bundle - not very unnatural for Eclipse apps
> b) a loooot of reexports!

Lots of reexports did cause issues in Luna, but should be fixed in SR2.  We got a fix for Felix issue https://issues.apache.org/jira/browse/FELIX-4762 which got released to SR2 and Mars.

> Would it be possible to:
> a) replace the lists through sets? This should improve the contains check
> b) use better initial array sizes?

I'm open to these types of changes if we can show they help improve the resolution time.  We will need to get the contributions back to apache, but I can handle that if you have some suggested changes.  Also note that we are having other issues in Mars that are not in Luna with 'batch' resolution.  This was supposed to help with performance but can cause the felix resolver algorithm to explode.  Any help there would be appreciated also.  See https://bugs.eclipse.org/bugs/show_bug.cgi?id=460393

> Tom
> --
> Thomas Schindl, CTO
> BestSolution.at EDV Systemhaus GmbH
> Eduard-Bodem-Gasse 5-7, A-6020 Innsbruck
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