On 8/26/2014 11:07 AM, Óscar Fuentes wrote:
"Raffaello D. Di Napoli"
<[email protected]> writes:
2014-08-25 11:25 GMT-04:00 Óscar Fuentes <[email protected]>:
On a CPU-intensive application, the 64 bit exe runs 40% slower than
its 32 bit counterpart. It's a C++ app with a workload typical of a
compiler.
Are there known slow spots on the 64 bit runtimes?
You mean, other than the fact that all your pointers (you say
compiler, so you probably use a lot of them in your data structures)
are twice as large and effectively reduce the effective size of your
processor’s data cache?
Yes, there are lots of pointers. The 64 bit executable uses almost 40%
more memory than the 32 bit executable. Perhaps it is not all that
coincidental that it is slower by the same factor.
One important thing I omitted was that I'm using Windows 8.1 64 bits
running on VMWare Workstation with Kubuntu 14.04 as host. The same app
running on Linux as 64 bits, compiled by gcc 4.8.2, runs twice faster
than when running on the Windows VM on 64 bit mode. The performance
penalty imposed by VMWare for single-threaded, CPU-bound processes is
much lower on my experience.
I'll try on a real Windows 64 bit machine as soon as I have access to
one, but I'm afraid that the 32bit vs 64bit slowdown is not caused by
VMWare.
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I was informed that 64-bit binaries on windows run faster actually due
to WOW64's 32-bit translation (layer?).
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Computer memory/disk size measurements:
[KB KiB] [MB MiB] [GB GiB] [TB TiB]
[10^3B=1,000B=1KB][2^10B=1,024B=1KiB]
[10^6B=1,000,000B=1MB][2^20B=1,048,576B=1MiB]
[10^9B=1,000,000,000B=1GB][2^30B=1,073,741,824B=1GiB]
[10^12B=1,000,000,000,000B=1TB][2^40B=1,099,511,627,776B=1TiB]
Note: disk size is measured in MB, GB, or TB, not in MiB, GiB, or TiB.
computer memory (RAM) is measured in MiB and GiB.
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