Optimizing TLB entries for mixed page size storage in contiguous memory
A system and method for accessing memory are provided. The system comprises a lookup buffer for storing one or more page table entries, wherein each of the one or more page table entries comprises at least a virtual page number and a physical page number; a logic circuit for receiving a virtual address from said processor, said logic circuit for matching the virtual address to the virtual page number in one of the page table entries to select the physical page number in the same page table entry, said page table entry having one or more bits set to exclude a memory range from a page.
1. A system for accessing memory comprising:
a processor device issuing a request for a memory page at a virtual address;
a translation look-aside buffer (TLB) for storing one or more page table entries, wherein each of the one or more page table entries maps said virtual address to a physical address, and a table entry providing an exclusion bit indicating a memory sub-region to be excluded from within said requested memory page;
a logic circuit for receiving a virtual address from said processor device, said logic circuit for matching the virtual address to a virtual page number in one of the page table entries to select the physical page number in the same page table entry,
wherein said memory sub-region of the requested memory page is available for subsequent filling with one or more smaller fixed-size memory pages.
2. The system of claim 1 , wherein said exclusion bit is set to a logic 1 to allow the predetermined memory range to be excluded from the page.
3. The system of claim 2 , wherein the virtual page number comprises one or more least significant bits, said least significant bits used to exclude the virtual address from matching the virtual page number, therefore excluding the memory range from the page.
4. The system of claim 3 , wherein said logic circuit comprises a comparator and the logic circuit uses said comparator to compare one or more bits in the virtual address at the same bit positions to said one or more least significant bits in the virtual page number in each of the one or more page table entries.
5. The system of claim 2 , wherein said logic circuit comprises a comparator and the logic circuit uses said comparator to evaluate the value of the exclusion bit.
6. The system of claim 1 , wherein said logic circuit comprises a first comparator for matching one or more most significant bits within the virtual address to bits within the virtual page number in one page table entries to select the physical page number and a second comparator for matching one or more least significant bits with the virtual address to bits within the page number to exclude said memory range from the page.
7. The system of claim 6 , wherein said logic circuit further comprises: a third comparator for evaluating the exclusion bit and when the exclusion bit is set to 1 causing the memory range to be excluded from the page.
8. The system of claim 2 , wherein other page table entries comprise bits for accessing the memory range excluded from the page.
9. The system of claim 2 , wherein said exclusion bit is set to logic 0to allow access to the entire page.
10. The system of claim 1 , wherein said fixed-size page sizes filled in the sub-region are page size aligned.
11. The system of claim 1 , wherein said fixed-size page sizes filled in the sub-region do not overlap.
12. The system of claim 1 , wherein said memory sub-region to be excluded is smaller than a page size of the table entry, said memory sub-region being configurable to M×4 KB, where M=1 to (TLB table entry page size in bytes/2 12 )−1.
13. The system of claim 1 , wherein said fixed-size page sizes filled in the sub-region are page size aligned.
14. A method for accessing memory comprising:
receiving at a logic device a virtual address; and
matching the virtual address to a virtual page number in one of one or more page table entries stored in a translation look-aside buffer (TLB) table to select a physical page and translate the virtual address to a physical address, a TLB entry providing an exclusion bit indicating a memory sub-region to be excluded from within said physical page;
wherein said memory sub-region of said physical page is available for subsequent filling with one or more smaller fixed-size memory pages.
15. The method of claim 14 , wherein the virtual address comprises one or more most significant bits and one or more least significant bits, and each of the one or more page table entries comprises a virtual page number and a physical page number, the method further comprising:
matching bitwise the one or more most significant bits to the virtual page number to select the physical page number; and
matching bitwise the one or more least significant bits to the virtual page number to exclude the memory range in the page.
16. The method of claim 15 , wherein the exclusion bit, is set to logic 1the method further comprises:
comparing one or more least significant bits within said virtual address to the virtual page number to exclude the predetermined memory range in the page.
17. The method of claim 16 , wherein other page table entries comprise bits for accessing the memory range excluded from the page.
18. The method of claim 15 , wherein said exclusion bit is set to logic 0to allow accessing the entire page.
19. The method of claim 14 , wherein said fixed-size page sizes filled in the sub-region do not overlap.
20. The method of claim 14 , wherein said memory sub-region to be excluded is smaller than a page size of the table entry, said memory sub-region being configurable to M×4 KB, where M=1 to (TLB table entry page size in bytes/2 12 )−1.