Re: [PATCH] Mantaining turnstile aligned to 128 bytes in i386 CPUs

On Jan 18, 2007, at 1:57 PM, Maxim Sobolev wrote:
Heh, it's so complex, so machine-dependent....

Well, yes. :)

That makes me wonder why we still don't have 3 simple to use instructions that do equivalent of memmove(), memcpy() and memset() all in hardware in the best possible way with the respect of block size, alignment, caches, chipset, you-name-it? Virtually every program would benefit from such instructions.

Unfortunately, there are simply different tradeoffs between mechanisms for copying depending on whether you want to use or avoid using/thrashing the L1/L2 caches, whether the data is cache-aligned, and so forth; the CPU can't infer what you want to occur-- you have to tell it. I find it interesting that some of the architectures (PA- RISC, SPARC) do allow for simple instructions with cache-control hinting:

http://gcc.gnu.org/projects/prefetch.html

--
-Chuck

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