On 28.02.2010 00:48, James Mansion wrote:
> Robert Jordan wrote:
>> It was an example why results might be different.
>>
>>
> Relevant?
Who?
>> It is not. The GC is interacting with low-level OS parts and can
>> be triggered any time during your benchmarks.
>>
> Lets back up, becuase I still think there has been some hand-waving. If
> the answer
> is really 'its stuck in GC and yes it sucks' then fine, but the speed
> difference
> is very large for this code, and it doesn't look right unless the
> Windows code is
> very bad. The order of magnitude difference is hard to explain by OS
> interface
> efficiency differences, unless the OS interfaces are being used badly.
Feel free to disassemble a method compiled under Windows
and Linux. You'll find no differences.
Now on TLS:
---
// compile with: cl /Od tls.c
#include <windows.h>
int __declspec(thread) foo;
int
main (void)
{
int i;
DWORD ticks;
DWORD tls = TlsAlloc ();
ticks = GetTickCount ();
for (i = 0; i < 100000000; i++) {
foo = i + 1;
}
printf ("elapsed %d for __thread\n", GetTickCount () - ticks);
ticks = GetTickCount ();
for (i = 0; i < 100000000; i++) {
TlsSetValue (tls, (LPVOID)(i + 1));
}
printf ("elapsed %d for TlsSetValue\n", GetTickCount () - ticks);
}
---
See the difference?
And yes, Mono is compiled w/out __thread support on Windows.
Patches are welcome ;)
Robert
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