Re: Warm-cache prefetching

Tom Lane wrote:
> Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > I can see that being useful for a single-user application that doesn't
> > have locking or I/O bottlenecks, and doesn't have a multi-stage design
> > like a database.  Do we do enough of such processing that we will _see_
> > an improvement, or will our code become more complex and it will be
> > harder to make algorithmic optimizations to our code?
> 
> The main concern I've got about this is the probable negative effect on
> code readability.  There's a limit to the extent to which I'm willing to
> uglify the code for processor-specific optimizations, and that limit is
> not real far off.  There are a lot of other design levels we can work at
> to obtain speedups that won't depend on the assumption we are running
> on this-year's Intel hardware.

That is my guess too.  We have seen speedups by inlining and optimizing
frequently-called functions and using assembler for spinlocks.  Proof of
the assembler is in /pg/include/storage/s_lock.h and proof of the
inlining is in /pg/include/access/heapam.h.  Those were chosen for
optimization because they were used a lot.

I think the big question is whether there are other areas that have a
similar CPU load and can be meaningfully optimized, and does the
optimization include such things as multi-staging.  I think we should
take a wait and see attitude and see what test results people get.

--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
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