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

[Thomas Watson <tjwatson@xxxxxxxxxx>]

> 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
> http://www.bestsolution.at/
> Reg. Nr. FN 222302s am Firmenbuchgericht Innsbruck
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