Messages in this thread | | | Date | Sat, 12 Nov 2011 13:08:06 -0500 | Subject | Cost of a Page Fault | From | Xin Tong <> |
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Hello All
My research project in university involves building and using custom processors as accerlerators. These processors are typically hooked into the system via a PCIE bus. Applications are compiled with the custom processor instruction set, when the x86 processor encounters these extended instructions, it will fault and linux kernel catches the fault and extract the custom processor instructions. While extracting the custom processor instructions is not too difficult, determining what memory the instructions are going to operate on is hard. One of the ideas I have in mind is by copying the page table of the faulty process to the custom processor. the custom processor has its own MMU and when the MMU tries to find a page and the page is not on the custom processor, it will generate a fault and a dma will be initiated to copy over the page from system memory.
Therefore, I would like to know the typical time of a dma from system memory to PCIE. It should be faster than a regular page fault because regular page fault involves copying from disk which in theory should be slower than PCIE devices.
Any comments on the cost of page fault and the project in general are appreciated.
Thanks
Xin
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