[OpenIndiana-discuss] Bash bug issue

[Bob Friesenhahn]

On Tue, 4 Nov 2014, david allan finch wrote:

> On 04/11/2014 03:36, Bob Friesenhahn wrote:
>> While it would be nice if Solaris software was all 64-bit, in actual 
>> practice I notice no difference in day to day use between systems with 
>> 32-bit applications and 64-bit.  Only certain memory-hungry
>> applications will significantly benefit. 
>
> We spent some time investigating this 10 years back and found that for most 
> apps that don't require the 64bit address space that they ran slower compiled 
> for 64bit. 64bit file access was of some us to us but the we stuck with 64bit 
> compiles and I expect that until CPU cache sizes increase a lot more there 
> will be no gain outside the OS (and DBs etc) for 99% of current apps.

The AMD64 ABI provides quite a lot more CPU registers than 32-bits. 
The function calling convention has changed to make better use of 
registers for passing values.  This places less stress on the CPU L1 
cache and allows the CPU to juggle more variables at once without 
doing loads/stores.

In performance benchmarks, I do usually see a performance gain due to 
compiling as 64-bits on x86 hardware.  Results are highly compiler 
dependent.

Regardless, most OS 'utilities' are not CPU bound and so the 
difference may not be measurable for normal use.

Bob
-- 
Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/