Messages in this thread | | | Subject | Re: Efficient IPC mechanism on Linux | From | Arjan van de Ven <> | Date | Wed, 10 Sep 2003 11:23:15 +0200 |
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On Wed, 2003-09-10 at 11:18, Luca Veraldi wrote:
> The overhead implied by a memcpy() is the same, in the oder of magnitude, > ***whatever*** kernel version you can develop.
yes a copy of a page is about 3000 to 4000 cycles on an x86 box in the uncached case. A pagetable operation (like the cpu setting the accessed or dirty bit) is in that same order I suspect (maybe half this, but not a lot less). Changing pagetable content is even more because all the tlb's and internal cpu state will need to be flushed... which is also a microcode operation for the cpu. And it's deadly in an SMP environment.
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