Identification and consolidation of page table entries

• US 9,092,359 B2
• Filed: 06/14/2012
• Issued: 07/28/2015
• Est. Priority Date: 06/14/2012
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Bybell, Anthony J., Gschwind, Michael K.
• Primary Examiner(s): BRAGDON, REGINALD GLENWOOD
• Assistant Examiner(s): Vo, Thanh D
• Application Number:
  US13/517,763
• Publication Number:
  US 20130339653A1
• Time in Patent Office: 1,139 Days
• Field of Search: 711206-208
• US Class Current: 1/1
• CPC Class Codes: G06F 12/1009 using page tables, e.g. page table structures
• CPC Class Codes: G06F 12/1027 using associative or pseudo-associative address translation means, e.g. translation look-aside buffer [TLB]
• CPC Class Codes: G06F 2212/652 Page size control

Abstract

A system for accessing memory locations includes translating, by a processor, a virtual address to locate a first page table entry (PTE) in a page table. The first PTE includes a marker and an address of a page of main storage. It is determined whether a marker is set in the first PTE. The system identifies a large page size of a large page associated with the first PTE based on determining that the marker is set in the first PTE. The large page consists of contiguous pages of main storage. An origin address of the large page is determined based on determining that the marker is set in the first PTE. The virtual address is used to index into the large page at the origin address to access main storage.

Claims

1. A computer program product for managing page table entries in a processing system, the computer program product comprising:

a non-transitory computer readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising;

translating, by a processor, a virtual address to locate a first page table entry (PTE) in a page table, the first PTE comprising a marker and an address of a page of main storage, wherein the first PTE points to a first page;

determining, with the processor, whether the marker is set in the first PTE;

identifying a large page size of a large page associated with the first PTE based on determining that the marker is set in the first PTE, wherein the large page consists of contiguous pages of main storage and the identifying includes determining the large page size based on content of a configuration register;

determining a second PTE that is distinct from the first PTE, that points to a second page that is contiguous to the first page, and that comprises a start location of the large page based on determining that the marker is set in the first PTE, wherein the large page comprises the first page and the second page;

obtaining the start location from the second PTE; and

using the virtual address to index into the page table at the start location to access the large page in main storage.

2. The computer program product of claim 1, wherein a range of virtual addresses identify corresponding PTEs comprising said first PTE, wherein each PTE of said corresponding PTEs is configured to address a respective page of main storage, each of said pages of main storage being contiguous.

3. The computer program product of claim 1, wherein the method further comprises:

storing virtual address information and an address for locating said large page, in a translation look-aside buffer (TLB); and

using the TLB to translate virtual addresses to large pages.

4. The computer program product of claim 1, wherein the determining the large page size is further based on marker bits in a plurality of contiguous PTEs associated with a corresponding block of virtual addresses on a block boundary.

5. The computer program of claim 1, wherein each of a plurality of PTEs corresponding to the large page comprises a respective address of a corresponding respective page of main storage, and wherein the respective pages of each of the plurality of PTEs are contiguous.

6. The computer program product according to claim 1, wherein the method further comprises:

identifying a single page associated with the first PTE based on determining that the marker is not set in the first PTE; and

using the virtual address to index into the page table to access the single page in main storage.

7. The computer program product according to claim 1, wherein the translating comprises any one of using a hierarchical set of translation tables to locate the PTE or using a hashing function to locate a group of PTEs, the group of page table entries comprising the PTE corresponding to the virtual address.

8. The computer program product of claim 1, wherein the determining the start location of the large page includes performing a logic operation that includes the large page size, the address of the page of main storage, and the virtual address as inputs.

9. The computer program product of claim 1, wherein the second PTE comprises a first physical address field that stores the start location of the large page, and wherein the first PTE comprises a second physical address field that stores additional page properties of the large page comprising the first page and the second page, and wherein the start location in the first physical address field is a different value from the additional page properties in the second physical address field.

10. A computer system for accessing a memory location, the system comprising:

a memory; and

a processor coupled to the memory, the computer system configured to perform a method comprising;

translating, by the processor, a virtual address to locate a first page table entry (PTE) in a page table, the first PTE comprising a marker and an address of a page of main storage, wherein the first PTE points to a first page;

determining whether the marker is set in the first PTE;

identifying, by the processor, a large page size of a large page associated with the first PTE based on determining that the marker is set in the first PTE, wherein the large page consists of contiguous pages of main storage and the identifying includes determining the large page size based on content of a configuration register;

determining a second PTE that is distinct from the first PTE, that points to a second page that is contiguous to the first page, and that comprises a start location of the large page based on determining that the marker is set in the first PTE, wherein the large page comprises the first page and the second page;

obtaining the start location from the second PTE; and

using the virtual address to index into the page table at the start location to access the large page in main storage.

11. The system of claim 10, wherein a range of virtual addresses identify corresponding PTEs comprising said first PTE, wherein each PTE of said corresponding PTEs is configured to address a respective page of main storage, each of said pages of main storage being contiguous.

12. The system of claim 10, wherein the method further comprises:

storing virtual address information and an address for locating said large page, in a translation look-aside buffer (TLB); and

using the TLB to translate virtual addresses to large pages.

13. The system of claim 10, wherein the determining the large page size is further based on marker bits in a plurality of contiguous PTEs associated with a corresponding block of virtual addresses on a block boundary.

14. The system of claim 10, wherein each of a plurality of PTEs corresponding to the large page comprises a respective address of a corresponding respective page of main storage, and wherein the respective pages of each of the plurality of PTEs are contiguous.

15. The system of claim 10, wherein the method further includes:

identifying a single page associated with the first PTE based on determining that the marker is not set in the first PTE; and

using the virtual address to index into the page table to access the single page in main storage.

16. The system of claim 10, wherein, the translating comprises any one of using a hierarchical set of translation tables to locate the PTE or using a hashing function to locate a group of PTEs, the group of page table entries comprising the PTE corresponding to the virtual address.

17. The system of claim 10, wherein the determining the start location of the large page includes performing a logic operation that includes the large page size, the address of the page of main storage, and the virtual address as inputs.

18. The system of claim 10, wherein the second PTE comprises a first physical address field that stores the start location of the large page, and wherein the first PTE comprises a second physical address field that stores additional page properties of the large page comprising the first page and the second page, and wherein the start location in the first physical address field is a different value from the additional page properties in the second physical address field.