Alex Turner wrote:
Anyone who has tried x86-64 linux knows what a royal pain in the ass it
is. They didn't do anything sensible, like just make the whole OS 64
bit, no, they had to split it up, and put 64-bit libs in a new directory
/lib64. This means that a great many applications don't know to check
in there for libs, and don't compile pleasantly, php is one among them.
I forget what others, it's been awhile now. Of course if you actualy
want to use more than 4gig RAM in a pleasant way, it's pretty much
essential.
That depends entirely on what AMD64 distribution you use -- on a Debian
or Ubuntu 64-bit system, the main system is pre 64-bit, with some
(optional) add-on libraries in separate directories to provide some
32-bit compatibility.
On the performance stuff, my own testing of AMD64 on AMD's chips (not
with PostgreSQL, but with various other things) has shown it to be about
10% faster on average. As Luke mentioned, this isn't because of any
inherent advantage in 64-bit -- it's because AMD did some tweaking while
they had the hood open, adding extra registers among other things.
I remember reading an article some time back comparing AMD's
implementation to Intel's that showed that EM64T Xeons ran 64-bit code
about 5-10% more slowly than they ran 32-bit code. I can't find the link
now, but it may explain why some people are getting better performance
with 64-bit (on Opterons), while others are finding it slower (on Xeons).
Thanks
Leigh
Alex.
On 6/12/06, *Steve Atkins* <steve@xxxxxxxxxxx
<mailto:steve@xxxxxxxxxxx>> wrote:
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.
An Opteron is 64 bit capable; that doesn't mean you have to run 64 bit
code on it.
Mine're mostly reasonably conservative users, with hundreds of machines
to support. Using 64 bit capable hardware, such as Opterons, is one
thing,
but using an entirely different linux installation and userspace
code, say, is
a much bigger change in support terms. In the extreme case it makes no
sense to double your OS support overheads to get a single digit
percentage
performance improvement on one database system.
That's not to say that linux/x86-64 isn't production ready for some
users, just
that it's not necessarily a good operational decision for my
customers. Given
my internal workloads aren't really stressing the hardware they're on
I don't
have much incentive to benchmark x86-64 yet - by the time the numbers
might be useful to me we'll be on a different postgresql, likely a
different
gcc/icc and so on.
Cheers,
Steve
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