Review Request: speed up of rxx_allocator

[David Nolden]

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The improvements you report from duchainify are far too huge, allociation has never played such a huge role during parsing. The problem is probably, that during the first (slow) run the duchain is built, then it is stored, and during the next run, it's only updated.

Please make sure that:
A) You call duchainify twice for each case, and use the second timing
B) You always use the "--force-update-recursive" parameter, which should eliminate the duchain caching issues

This issue also explains why you have observed the 50x difference in the number of calls to "new". From what I understand, you've changed the implementation of "new", so it shouldn't affect that number, or did I misunderstand that?

- David


On Feb. 24, 2011, 1:47 a.m., Floris Ruijter wrote:
> 
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> This is an automatically generated e-mail. To reply, visit:
> http://git.reviewboard.kde.org/r/100730/
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> 
> (Updated Feb. 24, 2011, 1:47 a.m.)
> 
> 
> Review request for KDevelop.
> 
> 
> Summary
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> 
> rxx_allocator was according to my measurements done with kcachegrind, valgrind, duchainify and iostream. The allocator had three basic defects:
> 1) all allocated memory was deallocated whilst we need a lot of rxx_allocators (1 per file i presume?), so these blocks can be reused
> 2) it cleared the memory on a per block basis, but if not all of the block is used, then that is a waste of effort
> 3) it used realloc to manage the list of blocks, this isn't too bad but could cause a move of the list which is totaly unnecessary
> 
> i solved the problems mostly by making the blocks act as linked list nodes: a next pointer + a really long char array. deallocated blocks are kept in a static linked list, whilst actual rxx_allocators have their own(personal some would say)linked list of blocks. access to the deallocated blocks list is synchronized through a static QMutex.
> 
> the access could be threadsafe by using a thread local linked list of deallocated items too, but i don't think that'd be practical, the global static list is probably more effective (eventhough it requires locking) 
> 
> 
> Diffs
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> 
>   languages/cpp/codecompletion/item.cpp b25d1ae 
>   languages/cpp/cppparsejob.cpp f4819f2 
>   languages/cpp/parser/ast.h 0281c6b 
>   languages/cpp/parser/control.h 0b06248 
>   languages/cpp/parser/listnode.h d1eda36 
>   languages/cpp/parser/parser.cpp 281ad8d 
>   languages/cpp/parser/rxx_allocator.h f0159e9 
>   languages/cpp/parser/tests/test_parser.cpp de5f804 
> 
> Diff: http://git.reviewboard.kde.org/r/100730/diff
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> 
> Testing
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> 
> as mentioned i ran a file which only included iostream through duchainify which i callgrinded.
> 
>                       old:              new: 
> pool::allocate        ~450 000 000      ~7 000 000
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> all time spend in libkdev4cppparser:
>                       ~585 000 000      ~140 000 000
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> 
> the pool::allocate numbers are both the 'inclusive' numbers
> 
> looking at the data for the amount of "operator new" calls I can see that the cost per call are pretty much the same but that the old implementation called it about 50x more.
> 
> 
> Thanks,
> 
> Floris
> 
>

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