RE: [cdt-dev] CDT performance

["Krasilnikov, Oleg" <oleg.krasilnikov@xxxxxxxxx>]

Hi all.

I am not sure whether the thing described below is useful or not.
What do you think, is it reasonable to continue this work,

In brief, there are a lot of complains about CDT indexing speed.
After process tracing, the following results are obtained:

- approximately 2/3 of time is consumed by "parser.parse()" operation.
  It is not a secret. May be this process can be enchanced, but now I
  have no exact proposals. See further section.

- approximately 1/4 of time is consumed by
"CGenerateIndexVisitor.visit(..)" calls.  
  In fact, these methods are called very frequently. For example, when I
have tried 
  with small C project (Midnight Commander source, 125 files), calls to
visit(..)
  were performed ~140 000 times. So it seems to be reasonable to tune up
this
  code as much as possible. 

I've tested some minor changes today. Details are below.
Totally, they can save ~1-2% of indexing time, according to my
measurements. 
It's not too much, but work is not finished now.

My question is: 
should corresponding BugZilla ID be created, 
or all these things are useless at all ?

------------------------------------------------------------------------
-----------
All changes are related to package
org.eclipse.cdt.internal.core.index.domsourceindexer

1.	CGenerateIndexVisitor.getFullyQualifiedName():

Avoid calling "name.resolveBinding()" - instead pass it from
processNameBinding(), 
where it's already obtained.

2.	CGenerateIndexVisitor.processNameBinding():

Avoid calling "IndexEncoderUtil.getFileLocation(name)", 
because direct call to "name.getFileLocation()" returns the same value;
Currently used static method is only wrapper around it.

3.	CGenerateIndexVisitor.processNameBinding():

Reorder if..elseif blocks according to their statistical frequency:

if (name.isReference())
else if (name.isDefinition())
else if (name.isDeclaration())

if (binding instanceof IVariable && !(binding instanceof IParameter)) 
else if (binding instanceof IFunction) 
else if (binding instanceof IField) 
else if (binding instanceof ITypedef)
else if (binding instanceof IEnumerator)
else if (binding instanceof ICompositeType)
else if (binding instanceof IEnumeration)

4.	CGenerateIndexVisitor.processNameBinding():

Avoid calling "name.getTranslationUnit().getScope()" for each variable.
Instead, store it in class variable and initialize it in object
constructor.
(since CGenerateIndexVisitor object is created for separate translation 
unit, we can assume that scope value will be constant during object 
lifetime).

5.	IndexEncoderUtil.nodeInVisitedExternalHeader() 

Currently, only the last file name is remembered.  In case of names
interchange 
(stdio.h string.h stdio.h string.h etc) caching does not work, and full
checks are
performed again and again. It affects ~10% of 

Providing level 2 cache (in ArrayList) can help to avoid extra
operations.

Statistics:
Total calls: ~165 000 
Repeated last name: 148 767 (already implemented)
Name in L2 cache:     14 421 (to be implemented)
New names:                2 384 (full check is performed)

Note: mentioned method is static. I cannot imagine how it can work with
multithreads.
So it seems like this functionality needs to be reviewed in general.

6.	To be continued with:

- parse()
- CPPGenerateIndexVisitor specific
- and so on.
-----------------------------------
With best regards, Oleg Krasilnikov
Software designer, Eclipse team. 
Intel corp.
+7 8312 162 444 ext. 2587 
(Russia, Nizhny Novgorod)