[mythtv-users] 32 vs. 64 bit, any significant difference?

belcampo belcampo at zonnet.nl
Thu Dec 17 22:21:54 UTC 2009


Robin Hill wrote:
> On Thu Dec 17, 2009 at 08:31:59PM +0100, belcampo wrote:
> 
>> Johnny wrote:
>>> Another benefit is that the compiler can make much more efficient
>>> optimizations because x86-64 includes all the modern changes to the
>>> x86 ISA (SSE etc) that modern chips support. When you use 32-bit it is
>>> compiled against the ISA that an Intel 386 used or maybe a 686 (e.g.
>>> Pentium II, Pentium III). But I think in everyday use you aren't
>>> likely to feel much difference from this (approximately 5%
>>> improvement). But in processes that are very computationally intense
>>> and benefit from newer ISA changes like SSE, then you will see larger
>>> improvements on the order of 10%-20%. Much of the MMX and SSE
>>> extensions added op-codes for vector operations, etc, that are
>>> targeting at multimedia stuff like transcoding. So that is one of the
>>> areas that sees the most benefit.
>> Are there any hard facts that prove these assumptions ?
>> Transcoding 32 vs 64bit 512MB vs 2-8GB
>>
> There's some transcoding figures at:
> http://hans.fugal.net/blog/2008/04/20/64-bit-transcoding/
> 
> Not transcoding, but there's some comparisons of other operations at:
> http://tuxradar.com/content/ubuntu-904-32-bit-vs-64-bit-benchmarks
> 
> AMD have some a good general comparison at:
> http://forums.amd.com/devblog/blogpost.cfm?threadid=93648&catid=317
Thanks for the links. 5-10% and
First there is the larger memory footprint. Binaries get larger because 
of an increased pointer size and 64-bit operands. This leads to higher 
memory transfer load and therefore increases cache utilization.
 From my observations over the last >20 years, only an increase of >30% 
is noticed by an avarage user. A faster/less-loaded disk often helps 
more in responsivnes, hence my < 350MB total installation-size and 
memory use as
free -m
              total       used       free     shared    buffers     cached
Mem:           487        478          8          0          0        301
-/+ buffers/cache:        177        309
Swap:            0          0          0

used for:
  4924 mythtv    15   0  214m  70m  22m S    0 14.5   0:11.87 
firefox-bin
  4018 root      15   0  241m  31m 8512 S    0  6.4   0:19.23 
mythbackend
  3766 root      15   0 61360  22m 6420 S    1  4.7   0:17.62 X 

  3784 mysql     16   0  113m  19m 4816 S    0  4.0   0:06.86 mysqld 

  3777 root      15   0 15224 5944 3476 S    0  1.2   0:00.02 httpd 

  3885 mythtv    16   0 10956 5440 3600 S    0  1.1   0:00.36 wmaker 


> 
> Cheers,
>     Robin
> 
> 
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