Software management systems and methods for automotive computing devices

• US 20020116588A1
• Filed: 12/20/2000
• Published: 08/22/2002
• Est. Priority Date: 12/20/2000
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Drasnin, Sharon, Radko, Ronald Otto, Beckert, Richard Dennis
• Granted Patent: US 6,801,994 B2
• Time in Patent Office: Days
• US Class Current: 711/161
• CPC Class Codes: G06F 11/1441 Resetting or repowering
• CPC Class Codes: G06F 11/2015 Redundant power supplies power supply failure G06F1/30
• CPC Class Codes: G06F 12/08 in hierarchically structured memory systems, e.g. virtual memory systems
• 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 12/122 of the least frequently used [LFU] type, e.g. with individual count value
• CPC Class Codes: G06F 2212/2022 Flash memory

Abstract

Methods and systems for operating automotive computing devices are described. In one embodiment, a small amount of static RAM (SRAM) is incorporated into an automotive computing device. The SRAM is battery-backed to provide a non-volatile memory space in which critical data, e.g. the object store, can be maintained in the event of a power loss. Circuitry is provided to ensure that the SRAM receives back up power from the battery at appropriate times. Software manages the SRAM and the other storage assembly components and makes use of virtual paging or virtual addressing techniques to keep track of where various pages, including object store pages, are stored in the system. The software knows where all of the object store pages are located so that in the event of a power loss, the page locations are known and hence the pages can be used when power is restored. The SRAM is advantageously used to maintain so-called “dirty pages” or pages that have been written to so that these pages are not lost in the event of a power interruption. Additionally, the software can also provide an orderly means by which pages in the SRAM can be written out to flash memory thereby avoiding unnecessary flash write operations which, in turn, increases the lifetime of the flash memory.

Claims

1. A method of operating an automotive computing device comprising:

providing an automotive computing device having a processor, volatile memory, non-volatile memory, and SRAM;

providing an object store for the computing device in the non-volatile memory; and

maintaining one or more pages from the object store in the SRAM.

2. The method of claim 1, wherein said maintaining is performed responsive to a detected power loss.

3. The method of claim 1 further comprising paging object store pages on demand into volatile memory.

4. The method of claim 1 further comprising writing one or more pages from volatile memory into SRAM.

5. The method of claim 4, wherein said writing comprises doing so responsive to accessing a page for the purpose of writing to the page.

6. The method of claim 1 further comprising writing one or more pages from volatile memory into a DRAM buffer allocated for that purpose.

7. The method of claim 1, wherein said providing of the object store comprises copying the object store into the non-volatile memory on an initial boot up of the device.

8. The method of claim 1, wherein the non-volatile memory comprises flash memory.

9. The method of claim 1 further comprising providing pages from the SRAM into the non-volatile memory in a predetermined manner.

10. The method of claim 1 further comprising maintaining an object store page table in SRAM, the object store page table providing data associated with the location of object store pages.

11. The method of claim 10 further comprising updating the object store page table in SRAM whenever an object store page is moved from one medium to another.

12. The method of claim 1 further comprising maintaining an object store page table in DRAM, the object store page table providing data associated with the location of object store pages.

13. The method of claim 1 further comprising battery-backing the SRAM in the event of a power loss.

15. The method of claim 14, wherein said acts of providing comprise doing so using virtual addressing techniques.

16. The method of claim 14 further comprising paging object store pages from the non-volatile storage into DRAM responsive to a page being accessed.

17. The method of claim 16, wherein the non-volatile storage comprises flash memory.

18. The method of claim 16, wherein said paging comprises determining whether a page that is attempted to be accessed is already in DRAM or SRAM, and if not in either, paging it in from the non-volatile memory.

19. The method of claim 18 further comprising updating a translation look-aside buffer to contain a new mapping for a virtual address of at least one page that has been paged in.

20. The method of claim 14 further comprising maintaining an object store page table in the SRAM, or a region of the DRAM buffer that can be backed up to non volatile memory on shutdown, the object store page table maintaining information associated with the location of object store pages.

21. The method of claim 20 further comprising updating one or more entries in the object store page table responsive to said acts of providing.

22. The method of claim 20 further comprising using the object store page table to track the object store pages across power cycles.

23. The method of claim 14, wherein said providing of the pages from the SRAM or DRAM buffer, to the non-volatile storage comprises doing so in a predetermined manner.

24. One or more computer-readable media having computer-readable instructions thereon which, when executed by a computer, implements the method of claim 14.

27. The method of claim 26 further comprising updating the object store page table in the SRAM responsive to paging an object store page within the device.

28. The method of claim 26 further comprising battery-backing the SRAM in an event of a power loss.

29. The method of claim 26 further comprising paging object store pages from non-volatile memory to volatile memory responsive to accessing the pages in the non-volatile memory.

30. The method of claim 26 further comprising paging object store pages from DRAM to SRAM or to a separate DRAM buffer, in the event of a write access.

31. The method of claim 26 further comprising maintaining dirty object store pages in SRAM in the event of a power failure.

32. The method of claim 26 further comprising writing contents of a device DRAM to a device flash memory in a predetermined amount of time in the event of a power loss.

33. The method of claim 26 further comprising copying one or more dirty object store pages from SRAM to a device flash memory to make room in the SRAM for additional dirty object store pages.

34. The method of claim 26 further comprising copying one or more dirty object store pages from a device DRAM to a device flash memory to make room in the DRAM for additional dirty object store pages.

36. An automobile embodying the automotive computing device of claim 35.

39. The automotive computing device of claim 38, wherein the instructions cause the computing device to initialize the object store page table to indicate that object store pages are located in flash memory and are read only pages.

40. The automotive computing device of claim 38, wherein the instructions cause the computing device to:

page object store pages between and among the flash memory, device DRAM and the SRAM; and

update the object store page table to reflect new locations of the paged object store pages.

41. The automotive computing device of claim 40, wherein the instructions cause the computing device to page object store pages from the flash memory to the DRAM responsive to a read access of the object store page.

42. The automotive computing device of claim 41, wherein the instructions cause the computing device to maintain a copy of one or more paged pages in the flash memory in the event of a power loss.

43. The automotive computing device of claim 40, wherein the instructions cause the computing device to page object store pages from the DRAM to the SRAM responsive to a write access of the object store page.

44. The automotive computing device of claim 40, wherein the instructions cause the computing device to page object store pages from the SRAM to the flash memory in a predetermined manner to make room for additional object store pages.

45. The automotive computing device of claim 38, wherein the instructions cause the computing device to use the object store page table to track whether an object store page is dirty.

46. The automotive computing device of claim 38, wherein the instructions cause the computing device to use the object store page table to track the number of times an object store page has been written to flash memory.

47. The automotive computing device of claim 46, wherein the instructions cause the computing device to use said number to determine when to write a page from the SRAM into the flash memory.

48. An automobile embodying the automotive computing device of claim 38.

50. An automotive computing device programmed with instructions which, when executed by the device, implement the method of claim 49.

51. An automobile embodying an automotive computing device programmed with instructions which, when executed by the device, implement the method of claim 49.

14. In an automotive computing device having non-volatile storage that can contain a system object store and DRAM that can receive object store pages, a method comprising:

providing one or more object store pages from the DRAM into an SRAM or separate DRAM buffer, comprising part of the automotive computing device; and

providing one or more pages from the SRAM or DRAM buffer into the non-volatile storage.

25. A programmable automotive computing device programmed with instructions which, when executed by the computing device, cause the computing device to:

move object store pages between and among non-volatile memory, volatile memory, and battery-backed SRAM;

maintain an object store page table in the SRAM that maintains information associated with the location of object store pages; and

update the object store page table responsive to moving object store pages.

26. In an automotive computing device, a method comprising:

maintaining a translation look-aside buffer that contains entries for recently translated virtual page addresses;

maintaining a page table in device memory that contains a map for every valid virtual page address; and

maintaining an object store page table in device SRAM that contains information associated with locations for every object store page.

35. A programmable automotive computing device programmed with instructions which, when executed by the computing device, cause the computing device to:

maintain a translation look-aside buffer that contains entries for recently translated virtual page addresses;

maintain a page table in device memory that contains a map for every valid virtual page address;

maintain an object store page table in device SRAM that contains information associated with locations for every object store page;

update the object store page table in the SRAM responsive to paging an object store page within the device;

flush pages from SRAM to another medium in a predetermined manner to make room for additional pages in the SRAM; and

battery-back the SRAM in an event of a power failure.

37. A programmable automotive computing device programmed with instructions which, when executed by the computing device, cause the computing device to:

maintain a translation look-aside buffer that contains entries for recently translated virtual page addresses;

maintain a page table in device memory that contains a map for every valid virtual page address;

maintain an object store page table in a dedicated DRAM buffer, the object store page table containing information associated with locations for every object store page;

update the object store page table in the DRAM buffer responsive to paging an object store page within the device;

flush pages from the DRAM buffer to another medium in a predetermined manner to make room for additional pages in the DRAM buffer; and

copy an amount of data contained in the DRAM buffer to flash memory in the event of a power failure.

38. A programmable automotive computing device programmed with instructions which, when executed by the automotive computing device, cause the computing device to:

copy an object store into device flash memory; and

create an object store page table in device SRAM that is configured to track the locations of all of the object store pages in the device.

49. In an automotive computing device, a method comprising:

booting the computing device; and

responsive to said booting, processing an object store page table that is maintained in battery-backed SRAM, the object store page table being configured to track locations of all object store pages in the device, said processing comprising changing any entries in the object store page table that indicate an object store page is in device DRAM to an entry that indicates that the object store page is in device flash memory.

52. An automotive computing device programmed with instructions which, when executed by the device, cause the device to:

attempt to access a page that is not currently mapped in a translation look-aside buffer (TLB);

generate a TLB miss error exception;

call an exception handler to provide the handler with an opportunity to handle the exception;

determine, with the exception handler, whether the page comprises an object store page; and

if the page comprises an object store page, copy the page from device flash memory to either device DRAM or device SRAM.

53. The automotive computing device of claim 52, wherein the instructions cause the device to copy the page to DRAM if the access is a read access.

54. The automotive computing device of claim 52, wherein the instructions cause the device to copy the page to SRAM if the access is a write access.

55. The automotive computing device of claim 52, wherein the instructions cause the device to return to another exception handler with an indication that the exception was not processed if the page does not comprise an object store page.

56. The automotive computing device of claim 52, wherein the instructions cause the device to, responsive to copying the page from device flash memory to either device DRAM or device SRAM, update an object store page table in the SRAM to reflect the new location of the object store page.

57. The automotive computing device of claim 56, wherein the instructions cause the device to provide an indication in the object store page table that the object store page is dirty if the access was a write access.

60. The method of claim 59 further comprising returning to another exception handler with an indication that the exception was not handled if the page is not an object store page.

61. One or more computer-readable media having computer-readable instructions thereon which, when executed by an automotive computing device, implement the method of claim 59.

62. A programmable automotive computing device programmed with instructions which, when executed by the computing device, implement the method of claim 59.

58. One or more computer-readable media having computer-readable instructions thereon which, when executed by an automotive computing device, cause the computing device to:

attempt to access a page that is not currently mapped in a translation look-aside buffer (TLB);

generate a TLB miss error exception;

call an exception handler to provide the handler with an opportunity to handle the exception;

determine, with the exception handler, whether the page comprises an object store page;

if the page comprises an object store page, copy the page from device flash memory to either device DRAM or device SRAM; and

return to another exception handler with an indication that the exception was not processed if the page does not comprise an object store page.

59. In an automotive computing device, a method comprising:

generating a write exception in an attempt to write-access a page in device flash memory or device DRAM;

calling an exception handler to give the exception handler an opportunity to handle the write exception;

determining whether the page is an object store page;

if the page is an object store page, copying the page with the exception handler into device SRAM; and

updating an object store page table that is maintained in the SRAM to indicate that the page is now located in SRAM and that the page is dirty.

63. An automotive computing system comprising:

a central processing unit having a translation look-aside buffer that contains entries for recently translated virtual page addresses;

physical memory operably associated with the central processing unit and containing a page table that contains a map for every valid virtual page address; and

SRAM containing an object store page table that contains information associated with locations for every object store page in the event of a power failure.

64. In an automotive computing device, a method comprising:

maintaining multiple object store pages in device SRAM; and

periodically flushing one or more object store pages to device non-volatile memory to make room for additional object store pages.

65. The method of claim 64 further comprising battery-backing the SRAM in the event of a power loss.

66. The method of claim 64 further comprising battery-backing the SRAM in the event that a voltage, associated with operation of a vehicle that embodies the computing device, drops out of regulation.

67. The method of claim 64 further comprising tracking the frequency of object store page writes, and flushing object store pages that are least frequently written to, before object store pages that are more frequently written to.

68. The method of claim 64 further comprising determining when to flush pages as a function of how many free SRAM pages are available.

69. The method of claim 68 further comprising assigning multiple threads with different priorities to flush pages in accordance with their priorities.

70. The method of claim 69, wherein said assigning comprises assigning threads with low, medium, and high priorities.

71. In an automotive computing device, a method comprising:

providing flash memory arranged in blocks;

reserving at least one block for compaction;

copying one or more pages in one or more other blocks to the reserved block; and

erasing any blocks from which pages were copied to prepare the blocks for subsequent writes.

72. The method of claim 71 further comprising wear-leveling the flash memory by using a different free block for each successive compaction.

73. In an automotive computing device, a method of booting the device comprising:

booting the device by paging to RAM only object store pages from non-volatile memory that are necessary in order to boot the device; and

paging in other object store pages, after said booting, as the pages are needed by the device.

74. The booting method of claim 73, wherein the non-volatile memory comprises flash memory.

75. The booting method of claim 73 further comprising maintaining a copy of the object store in non-volatile memory from a previous boot of the device.

76. One or more computer-readable media having computer-readable instructions thereon which, when executed by an automotive computing device, cause the device to implement the method of claim 73.

77. An automotive vehicle having an automotive computing device that embodies the computer-readable media of claim 76.

79. The booting method of claim 78, wherein the RAM comprises DRAM.

80. The booting method of claim 78, wherein the RAM comprises SRAM.

81. The booting method of claim 78, wherein the RAM comprises battery-backed SRAM.

78. In an automotive computing device, a method of booting the device comprising:

maintaining a copy of an object store in flash memory that is carried by the automotive computing device;

initiating a boot sequence of the automotive computing device;

during the boot sequence, paging only predetermined object store pages from the flash memory into RAM that is carried by the automotive computing device, said predetermined pages comprising less than all of the pages in the entire object store;

after the boot sequence, determining whether any additional object store pages are needed from the flash memory; and

paging any needed object store pages from the flash memory into the RAM.