Re: [HACKERS] Profile of current backend

Can we go anywhere with this?

>
> Bruce Momjian wrote:
> >
> > Interesting. Nothing is jumping out at me. Looks like we could try to
> > clean up heapgettup() to see if there is anything in there that can be
> > speeded up.
> >
> > None of the calls looks like it should be inlined. Do you see any that
> > look good for inlining?
>
> 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?
>
>
> Guesstimate:
> This would speed up heapgettup() by 10% ???
> Other functions would speed up too.
>
>
> /* m */
>

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