Messages in this thread | | | From | (bill davidsen) | Subject | Re: x86, ARM, PARISC, PPC, MIPS and Sparc folks please run this | Date | 3 Sep 2003 17:36:41 GMT |
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In article <20030901020203.1779efe8.davem@redhat.com>, David S. Miller <davem@redhat.com> wrote:
| > This is my strategy: | > | > mmap MAP_ANON without MAP_FIXED to find a free area | > mmap MAP_FIXED over the anon area at same address | > mmap MAP_FIXED over the anon area at larger address | > | > I don't see any strategy that lets me establish this kind of circular | > mapping on Sparc without either (a) knowing the value of SHMLBA, or | > (b) risking clobbering another thread's mmap. | | Why do you need the same piece of data mapped to multiple places | in the first place, and why at specific addresses? It's purely an | optimization of some sort, right?
I think he said he was doing DSP... there's a trick of double mapping the same memory to save one subscript calculation in FFT (or maybe DFT) inner loop. The only reason I know this is that a friend did a master's thesis on DSP about 20 years ago, and I absorbed some info I hope to never need. He also coded an FFT instruction in the LCS (programmable firmware) of a VAX.
I am only speculating, of course. -- bill davidsen <davidsen@tmr.com> CTO, TMR Associates, Inc Doing interesting things with little computers since 1979. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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