Review Request: Enforce parse-jobs to be processed in order of their priorities

[David Nolden]

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I see two problems:
1. With this patch, a user editing the source-code (at least with the "sequential" flag enabled), would prevent any real background-parsing from happening, because the direct editing would repeatedly create a good-priority parsejob.
2. Thinking of it, the background-parse does not seem to be the right place for handling exact parsing-sequences, because it merges multiple parse-requests for the same document together. For example, if the background-parse once gets a request for file A with priority 0 and full processing-level, and additionally a request for the same file with priority 10 and partial processing-level, then the second request will be completely merged into the first, because it is (or at least seems) redundant.

Probably the right place to handle all these things would be a layer on top of the background-parser which would wait for finished parse-jobs, and schedule re-parses where required accordingly.

- David Nolden


On Feb. 25, 2012, 5:48 p.m., Sven Brauch wrote:
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> (Updated Feb. 25, 2012, 5:48 p.m.)
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> 
> Review request for KDevelop, Milian Wolff and David Nolden.
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> Description
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> As recently discussed on the mailing list, it is currently unnecessarily difficult to handle the following scenario:
> File A does something like "import B"; you want A to be parsed with the top-context for B available.
> Various language plugins have various solutions for this problem, but none of them were considered optimal by their creators (as far as I understood).
> 
> This patch aims to adress that problem. It changes the parsejob creation algorithm by enforcing it to wait with creating a job with a worse priority as long as jobs with a better priority are still running. Example: Three documents A, B and C are scheduled for parsing, A and B with priority 0 and C with priority -1. Assuming two parse jobs are available, the old function would create two parsejobs for C and A or B (let's say A), then wait for one of them to finish, then create a third job for B. The new function will create a parsejob for C and wait until that one is finished, and then create two jobs for A and B (still simultaneously, because they have the same priority). In other words: It's guaranteed that all parse jobs running at any specific time have the same priority. (*)
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> Why is that useful? Because parsejob priorities can be used to adress the above problem now: Let priority(x) be the priority of the parse-job for document x. You can then parse A, and as soon as you encounter the "import B", you can schedule B with priority(A)-1 and schedule A (again) with priority(A). That's now guaranteed to first parse B and then re-parse A with the top-context for B being available.
> Oh, this patch also adds a function to get a parseJobs ownPriority(), that wasn't available before.
> 
> Please tell me what you think.
> 
> Greetings,
> Sven
> ________
> (*) I'm aware of the fact that this will decrease performance by a little bit. However, I'm pretty sure it's not relevant. If the general concept of this is accepted, I'll test it.
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> 
> Diffs
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>   language/backgroundparser/backgroundparser.h 954ee17 
>   language/backgroundparser/backgroundparser.cpp 7210254 
>   language/backgroundparser/parsejob.h 135319c 
>   language/backgroundparser/parsejob.cpp 552ef68 
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> Diff: http://git.reviewboard.kde.org/r/104019/diff/
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> 
> Testing
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> 
> Thanks,
> 
> Sven Brauch
> 
>

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