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Re: Performance difference 32bit/64bit userland

On Tue, Feb 07, 2017 at 10:05:38PM +0200, Gatis Visnevskis wrote:
> Well explained!
> In enterprise world, Java applications will benefit from 64-bit addressing.
> Another example is Oracle, 32-bit server side is dropped while ago. So it
> also make sense to compile all Oracle client linked apps with 64-bit
> compiler. Might be offtopic, but all above is true also for AIX. Most
> binaries are 32-bit.

Certainly part of what has kept too much work going into ppc64 is probably
that 32 bit power pc with a 64 bit kernel gives the best performance
for most uses, and just installing a few things 64 bit where needed is
the best balance.  Sparc I believe has been similar in the past, where
64 bit kernel to allow more overall memory was useful, but keeping most
things user space 32 bit was the best for performance.

ppc64el is different since it is targeting systems where the applications
are expected to need a lot of ram, and switching the little endian
improves performance when working with GPUs (which are all designed
for the x86 little endian world).  At the same time being able to
assume power8 as a minimum cpu means you can gain some instruction set
improvements that normal powerpc can't assume.  ppc64 can't make such
assumptions since it will run on a much wider range of 64 bit powerpc

Len Sorensen

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