Cross-domain data transfer using deferred page remapping

• US 5,895,499 A
• Filed: 07/03/1995
• Issued: 04/20/1999
• Est. Priority Date: 07/03/1995
• Status: Expired due to Term

• Current Assignee: Oracle America, Inc. (Oracle Corporation)
• Original Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Inventors: Chu, Hsiao-keng J.
• Primary Examiner(s): Banankhah, Majid A.
• Assistant Examiner(s): CALDWELL, PATRICIA G
• Application Number:
  US08/497,816
• Time in Patent Office: 1,387 Days
• Field of Search: 395/400, 395/200.01-200.08, 395/680, 395/681-685, 711/202, 711/203, 364/200
• US Class Current: 711/202
• CPC Class Codes: G06F 12/1072 Decentralised address translation, e.g. in distributed shared memory systems

Abstract

A cross-domain data transfer technique is disclosed in which page remapping operations are eliminated in situations where physical memory addresses can be passed across domains. By passing physical memory addresses across domains instead of virtual memory addresses, the page remapping operations necessarily associated with passing virtual memory addresses across domains can be avoided in many cases. With the receipt of data across domains, page remapping operations are able to be deferred until the data is received in a domain that needs to touch the data. In certain cases, the transfer of data can be completed without ever having to map in the data to the receiving domain'"'"'s address space. With the transmission of data across domains, where possible the pages are borrowed in their physical form. The invention can be embodied in many ways, including system, apparatus or method forms.

Claims

1. A computer system, comprising:

a network adapter that connects to a network, said network adapter including circuitry for performing data checksum operations;

a computer and an operating system arranged to support multiple processes and multiple domains;

a main memory having at least a portion thereof arranged in pages; and

a virtual memory management unit, operatively connected to said computer and said memory, for managing reads and writes to said memory using page mapping information,

wherein said operating system controls ownership of the pages in said memory using page ownership information,

wherein said computer system enables the receipt of a physical page of data transferred between domains by reassigning ownership of the physical page within the page ownership information without updating the page mapping information associated with said virtual memory management unit until the domain obtaining ownership needs to read the data, such that burdensome page remapping operations are be avoided or at least deferred until needed,

wherein the transfer of the page of data is invoked by a data request,

wherein said operating system comprises means for determining whether the requested page of data being received is one of a virtual address request and a physical page memory request,

wherein when the requested page is the physical page memory request, said operating system controls the reassigning of ownership of the physical page within the page ownership information without updating the page mapping information, and

wherein when the requested page is the virtual address request, said operating system controls the reassigning of ownership of the physical page within page ownership information and said operating system together with said virtual memory management unit update the page mapping information.

2. A computer system as recited in claim 1, wherein the page mapping information includes data for translating virtual memory addresses to physical addresses.

3. A computer system as recited in claim 1, wherein said virtual memory management unit comprises a translation mapping device for mapping virtual memory addresses to physical addresses.

4. A computer system as recited in claim 1, wherein said operating system has physical buffers and virtual buffers associated with each of the multiple domains, the physical buffers point to said main memory and the virtual buffers point to virtual memory.

5. A computer system as recited in claim 4, wherein said network adapter receives incoming packets of data, each packet includes a header and data, and

wherein the header is placed in one of the virtual buffers and the data is placed one or more of the physical buffers.

6. A computer system as recited in claim 1, wherein said computer system enables the transmission of a physical page of data across domains by borrowing the physical page.

7. A computer system as recited in claim 6, wherein said computer system further enables the transmission of the physical page across domains by locking the page ownership information associated with the borrowed page while the physical page is being borrowed.

8. A computer system as recited in claim 7, wherein the original owner of the borrowed page is restricted to read-only access while the physical page is being borrowed.

9. A computer system as recited in claim 6, wherein said operating system has physical buffers and virtual buffers associated with each of the multiple domains, the physical buffers point to said main memory and the virtual buffers point to virtual memory.

10. A computer system as recited in claim 9, wherein said network adapter receives incoming packets of data, each packet includes a header and data, and

wherein the header is placed in one of the virtual buffers and the data is placed one or more of the physical buffers.

11. In a multitasking computer system supporting multiple domains and virtual memory, a method for transferring a block of data associated with a first domain to a second domain, said method comprising the steps of:

(a) receiving a request at a first domain from a second domain for a block of data residing on a portion of physical memory assigned to the first domain;

(b) reassigning ownership of the block of data requested from the first domain to the second domain;

(c) determining whether the block of data requested is one of a virtual address request and a physical memory request; and

(d) remapping virtual addresses in accordance with said reassigning step (b) when said determining step (c) determines that the data request is the virtual address request and not when said determining step (c) determines that the data request is the physical memory requests,

wherein burdensome remapping operations are avoided or at least deferred until said determining step (c) determines that a data request is a virtual address request for the reassigned block of data.

12. A method as recited in claim 11, wherein the physical memory includes a plurality of pages, and the portion of the physical memory storing the block of data is one or more pages of the physical memory.

13. A method as recited in claim 11, wherein the block of data is one or more pages of the physical memory, and the physical memory request is a physical page memory request.

14. A method as recited in claim 13, wherein said reassigning step (b) of ownership comprises flipping the physical page requested at the first domain with a physical page of the second domain.

15. A method as recited in claim 11, wherein the virtual address request is a read request that will need to touch the data, and the physical memory request is a read request that will not need to touch the data.

16. A method as recited in claim 15, wherein said remapping step (d) is deferred until a read request for the data being transferred needs to touch the data.

17. A method as recited in claim 15, wherein the first domain is a network domain and the second domain is a kernal domain.