better performance with 32 bit ! why?

[Kevin Oberman]

On Tue, Jun 28, 2011 at 7:32 AM, Ryan Novosielski <novosirj at umdnj.edu> wrote:
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> On 06/28/2011 12:30 PM, David Sparro wrote:
>> On 6/28/2011 11:15 AM, iharrathi.ext at orange-ftgroup.com wrote:
>>> Hi all,
>>> I'm testing the same version of bind 9.4-ESV-R4-P1 on two server, one is
>>> a 32 bit (on which i have a redhat 32 bit) and the second a 64 bit
>>> server on which i have a redhat 64 bit.
>>> on the 32 bit i reach 70000 qps but on the 64 bit i only reach 50000 qps
>>> (using resperf) and also with tcpreplay.
>>> Is it normal that bind when compiled and installed on a 32 bit server
>>> have better performance than bind when compiled and installed on a 64
>>> bit server.
>>> the only différence between the two server is 64 bit vs 32 bit ( same
>>> RAM, same Disk, same NIC,...) and CPU is better on the 64 bit (2 Intel
>>> E5310 quad-core 1.6Ghz) than the 32 bit(2 Intel Xeon duad-core 2.33Ghz).
>>> Thanks.
>>>
>>
>> The 32 bit rig is faster (2.33Ghz).
>
> My understanding is that 64-bit is NOT faster in most cases, and only
> makes some things possible (addressing large amounts of memory is one
> stand-out) that are not possible with 32-bit. If bind is not going to be
> using over 4GB of RAM by itself, my understanding is that running 64-bit
> will merely add overhead. I realize that is a pretty big generalization,
> so feel free to correct me if you know better.

I'll take it a step farther. In my experience running  code in 64-bit
mode is USUALLY slightly slower than running it in 32-bit mode on the
same hardware. This is mostly because of the added data that must be
moved for 64-bit operations. It also means the 64-bit binaries are
larger, often by a significant amount.

I recommend sticking with 32-bit systems unless you have a specific
need for 64-bit capacity.
-- 
R. Kevin Oberman, Network Engineer - Retired
E-mail: kob6558 at gmail.com