What is the reason of using 256 for prefetchnta?

[amosbird]

FastMemcpy/FastMemcpy.h

Line 644 in 8fea5f6

_mm_prefetch((const char*)(src + 256), _MM_HINT_NTA);

Hi, it bugs me as 128 seems to be a reasonable choice. Is that derived from experiments? Or something related to the mechanism of prefetching itself?

[zhengle2008]

FastMemcpy/FastMemcpy.h

Line 644 in 8fea5f6

_mm_prefetch((const char*)(src + 256), _MM_HINT_NTA);

Hi, it bugs me as 128 seems to be a reasonable choice. Is that derived from experiments? Or something related to the mechanism of prefetching itself?

It bugs me too. But I guess it's just an experimental value about how far to look ahead.

[ywgrit]

FastMemcpy/FastMemcpy.h

Line 644 in 8fea5f6

_mm_prefetch((const char*)(src + 256), _MM_HINT_NTA);

Hi, it bugs me as 128 seems to be a reasonable choice. Is that derived from experiments? Or something related to the mechanism of prefetching itself?

It bugs me too. But I guess it's just an experimental value about how far to look ahead.

I don't quite understand what the experimental value is in this case. Could you give an example?