Re: 64-bit vs 32-bit performance ... backwards?

On Jun 12, 2006, at 6:15 PM, Joshua D. Drake wrote:
>> Empirically... postgresql built for 64 bits is marginally slower  
>> than that built
>> for a 32 bit api on sparc. None of my customers have found 64 bit x86
>> systems to be suitable for production use, yet, so I've not tested  
>> on any
>> of those architectures.
>
> Really? All of our customers are migrating to Opteron and I have  
> many that have been using Opteron for over 12 months happily.



We have been using PostgreSQL on Opteron servers almost since the  
Opteron was first released, running both 32-bit and 64-bit versions  
of Linux.  Both 32-bit and 64-bit versions have been bulletproof for  
us, with the usual stability I've become accustomed to with both  
PostgreSQL and Linux.  We have been running nothing but 64-bit  
versions on mission-critical systems for the last year with zero  
problems.

The short story is that for us 64-bit PostgreSQL on Opterons is  
typically something like 20% faster than 32-bit on the same, and  
*much* faster than P4 Xeon systems they nominally compete with.   
AMD64 is a more efficient architecture than x86 in a number of ways,  
and the Opteron has enviable memory latency and bandwidth that make  
it an extremely efficient database workhorse.  x86->AMD64 is not a  
word-width migration, it is a different architecture cleverly  
designed to be efficiently compatible with x86.  In addition to  
things like a more RISC-like register set, AMD64 uses a different  
floating point architecture that is more efficient than the old x87.

In terms of bang for the buck in a bulletproof database server, it is  
really hard to argue with 64-bit Opterons.  They are damn fast, and  
in my experience problem free.  We run databases on other  
architectures, but they are all getting replaced with 64-bit Linux on  
Opterons because the AMD64 systems tend to be both faster and  
cheaper.  Architectures like Sparc have never given us problems, but  
they have not exactly thrilled us with their performance either.


Cheers,

J. Andrew Rogers