Re: [HACKERS] Profile of current backend

Bruce Momjian writes:
> Can we go anywhere with this?

Did anyone do anything with this already?

> > ExecScan() seems to be the only func which calls SeqNext(), which in
> > turn accounts for 60% of the calls to heap_getnext(), which does 80% of
> > the calls to heapgettup().
> >
> > - Put SeqNext() into ExecScan() to lower function call overhead? [minimal optim.]
> >
> > - In heapgettup(), 50% is the func itself and 50% is called funcs.
> > Top four CPU consumers:
> > 0.04 0.14 9924/9924 RelationGetBufferWithBuffer [148]
> > 0.03 0.15 5642/5702 ReleaseAndReadBuffer [145]
> > 0.10 0.00 26276/42896 nocachegetattr [158]
> > 0.01 0.08 7111/9607 HeapTupleSatisfiesVisibility [185]
> >
> > RelationGetBufferWithBuffer() seems to be called from here only. If so, inline.
> >
> > - Looking at RelationGetBufferWithBuffer():
> > 0.00 0.10 4603/32354 ReadBuffer [55]
> > ReadBuffer() is the biggest cpu consumer called by RelationGetBufferWithBuffer(). (55%)
> >
> > -> *** 97% of ReadBuffer() CPU time is in calling ReadBufferWithBufferLock()
> >
> > -> 85% of ReadBufferWithBufferLock() CPU time is in calling BufferAlloc().
> > -> ReadBufferWithBufferLock() is the only func calling BufferAlloc().
> > -> Conclusion: INLINE BufferAlloc().
> >
> > - Looking at BufferAlloc():
> > 0.04 0.25 37974/37974 BufTableLookup [114]
> > 0.10 0.00 32340/151781 SpinAcquire [81]
> > 0.10 0.00 37470/40585 PinBuffer [209]
> > 0.08 0.00 38478/43799 RelationGetLRelId [234]
> > 0.04 0.00 37974/151781 SpinRelease [175]
> >
> > -> 40% of BufferAlloc() CPU time is in calling BufTableLookup().
> > -> BufferAlloc() is the only func calling BufTableLookup().
> > -> Conclusion: INLINE BufTableLookup().
> >
> > - Looking at BufTableLookup():
> > 86% of CPU time is in calling hash_search(). The rest is own time.
> >
> > - Looking at hash_search():
> > 0.13 0.41 179189/179189 call_hash [69]
> > 0.00 0.00 6/6 bucket_alloc [1084]
> > -> Conclusion: INLINE call_hash() [and bucket_alloc()] into hash_search().
> >
> > - Looking at call_hash():
> > 0.37 0.00 171345/171345 tag_hash [94]
> > 0.04 0.00 7844/7844 string_hash [348]
> > -> Conclusion: INLINE tag_hash() [and string_hash()] into call_hash().
> > -> Perhaps disk_hash() could be used in some way? It is currently #ifdef'd away.
> > -> Could we use a lookup table instead of doing hash calculations? Would not that
> > -> be much faster?
> >
> >
> > It looks to me as if there are too many levels of function calls.
> > Perhaps all functions which are called by only one other func should be inlined?

Isn't this a good solution? A function only called by one other function has
its right to exist only for readability. And this optimization could be done
automatically.

Michael

--
Dr. Michael Meskes, Project-Manager | topsystem Systemhaus GmbH
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