Re: Warm-cache prefetching

Do these optimizations have any affect on database software? I know
call overhead shows up as a performance bottleneck, but do these others
optimizations also measurably improve performance?

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Simon Riggs wrote:
> This technique and others are discussed in detail in the Intel
> Optimization Manual:
> http://apps.intel.com/scripts-util/download.asp?url=/design/PentiumII/manuals/24512701.pdf&title=Intel%AE+Architecture+Optimization+Reference+Manual&fullpg=3&site=Developer
>
> Similar manual exists for AMD and other architectures.
>
> On Thu, 2005-12-08 at 23:07 -0500, Qingqing Zhou wrote:
> > I write a program try to simulate it, but I am not good at micro
> > optimization, and I just get a very weak but kind-of-stable improvement. I
> > wonder if any people here are interested to take a look.
>
> You may be trying to use the memory too early. Prefetched memory takes
> time to arrive in cache, so you may need to issue prefetch calls for N
> +2, N+3 etc rather than simply N+1.
>
> p.6-11 covers this.
>
> There's a lot of papers around coming up with interesting sounding
> techniques. AFAICS, all they've done is read the optimization guide and
> tried to apply that wisdom, so it seems a good idea to go back to the
> source.
>
> I think many of these techniques are generic across architectures, so
> there is much to be done in this area, IMHO. Though we must respect
> portability and confirm any tuning through testing.
>
> Best Regards, Simon Riggs
>
>
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