Systems and methods for memory failure prevention, management, and mitigation

• US 10,725,853 B2
• Filed: 12/30/2019
• Issued: 07/28/2020
• Est. Priority Date: 01/02/2019
• Status: Active Grant

• Current Assignee: Formulus Black Corporation
• Original Assignee: Formulus Black Corporation
• Inventors: Zhang, Yin, Abdul, Nafees Ahmed, Ni, Boyu, Kunta, Gautham Reddy, Khurshudov, Andrei, Sicola, Stephen J.
• Primary Examiner(s): Patel, Jigar P
• Application Number:
  US16/730,589
• Publication Number:
  US 20200210272A1
• Time in Patent Office: 211 Days
• CPC Class Codes: G06F 11/004 Error avoidance G06F11/07 and subgroups take precedence
• CPC Class Codes: G06F 11/073 in a memory management context, e.g. virtual memory or cache management memory management G06F12/00; testing of static memory units G11C29/00
• CPC Class Codes: G06F 11/076 by exceeding a count or rate limit, e.g. word- or bit count limit
• CPC Class Codes: G06F 11/0793 Remedial or corrective actions recovery from an exception in an instruction pipeline G06F9/3861; by retry G06F11/1402; for recovering from a failure of a protocol instance or entity H04L69/40
• CPC Class Codes: G06F 11/1666 where the redundant component is memory or memory area
• CPC Class Codes: G06F 11/34 Recording or statistical evaluation of computer activity, e.g. of down time, of input/output operation ; Recording or statistical evaluation of user activity, e.g. usability assessment
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 12/08 in hierarchically structured memory systems, e.g. virtual memory systems
• CPC Class Codes: G06F 12/126 with special data handling, e.g. priority of data or instructions, handling errors or pinning
• CPC Class Codes: G06F 2201/81 Threshold
• CPC Class Codes: G06F 2212/1032 Reliability improvement, data loss prevention, degraded operation etc
• CPC Class Codes: G06F 2212/502 using adaptive policy
• CPC Class Codes: G06F 3/0688 Non-volatile semiconductor memory arrays
• CPC Class Codes: G11C 2029/0409 Online test
• CPC Class Codes: G11C 29/4401 for self repair
• CPC Class Codes: G11C 29/52 Protection of memory contents; Detection of errors in memory contents
• CPC Class Codes: G11C 29/76 using address translation or modifications

Abstract

Some embodiments described herein are directed to memory page or bad block monitoring and retirement algorithms, systems and methods for random access memory (RAM). Reliability issues or errors can be detected for multiple memory pages using one or more retirement criterion. In some embodiments, when reliability errors are detected, it may be desired to remove such pages from operation before they create a more serious problem, such as a computer crash. Thus, bad block retirement and replacement mechanisms are described herein.

Claims

1. A computer-implemented method of monitoring and retiring memory pages in random access memory (RAM), the computer implemented method comprising:

monitoring, by a computer system, correctable error statistics for each of a plurality of memory pages, wherein the correctable error statistics comprise one or more page retirement criteria, wherein the one or more page retirement criteria comprise a correctable error count, correctable error rate, or a time since a most recent correctable error;

detecting, by the computer system, a high-risk page, wherein detecting the high-risk page comprises determining whether the page retirement criteria of the high-risk page has exceeded a retirement criteria threshold;

placing, by the computer system, page information associated with the high-risk page on a retired page list, wherein the retired page list has a size corresponding to a number of spare pages stored in a reserved space of RAM;

storing, by the computer system, identical data to data stored in the high-risk page in a spare page; and

identifying, by the computer system in a mapping of the plurality of memory pages, the high-risk page such that one or more references to the high-risk page in the mapping are rerouted to the spare page,

wherein the computer system comprises a processor and the RAM.

2. The computer-implemented method of claim 1, wherein the one or more page retirement criteria comprise a single page retirement criterion.

3. The computer-implemented method of claim 1, wherein the retirement criteria threshold comprises a predetermined, static threshold.

4. The computer-implemented method of claim 1, wherein the retirement criteria threshold comprises a dynamically calculated threshold.

5. The computer-implemented method of claim 4, wherein the dynamically calculated threshold is determined by calculating an outlier value based on a statistical distribution of the one or more page retirement criteria.

6. The computer-implemented method of claim 5, wherein the statistical distribution comprises a normal distribution.

7. The computer-implemented method of claim 5, wherein the outlier value is calculated using a formula comprising a mean and a standard deviation of the one or more page retirement criteria of the plurality of memory pages.

8. The computer-implemented method of claim 7, wherein the outlier value comprises M+Vσ

, wherein M comprises the mean, wherein V comprises a variable number, and wherein σ

comprises the standard deviation.

9. The computer-implemented method of claim 1, wherein the monitoring the correctible error statistics and the detecting a high-risk page are completed by a Central Faults Tolerance Manager (CFTM) of the computer system.

10. The computer-implemented method of claim 1, wherein the one or more page retirement criteria comprises a plurality of page retirement criterion.

11. The computer-implemented method of claim 1, further comprising reserving, by the computer system, the reserved space of RAM.

12. The computer-implemented method of claim 1, wherein the reserved space comprises:

a spare pages space comprising the spare pages; and

the retired page list.

13. The computer-implemented method of claim 1, wherein the RAM comprises:

a watched page list, wherein the page information associated with the high risk page is placed on the watched page list prior to placing the page information on the retired page list.

14. The computer-implemented method of claim 1, wherein the high-risk page is available for data allocation by the computer system prior to placing the page information on the retired page list.

15. The computer-implemented method of claim 1, wherein each of the plurality of pages comprises a 4 KB block of memory.

16. The computer-implemented method of claim 1, wherein the computer system comprises a RAM-based computer system without a hard disk drive or solid state drive.

17. The computer-implemented method of claim 1, wherein after the one or more references to the high-risk page in the mapping are rerouted to the spare page, the high-risk page is moved to the reserved space of RAM.

18. The computer-implemented method of claim 1, wherein the computer system does not allocate data to pages in the reserved space of RAM.

19. The computer-implemented method of claim 1, wherein the spare page is moved to an available space of RAM after the computer system stores the identical data in the spare page.

20. A computing system comprising:

one or more computer readable storage devices configured to store a plurality of computer executable instructions; and

one or more hardware computer processors in communication with the one or more computer readable storage devices and configured to execute the plurality of computer executable instructions in order to cause the system to;

monitor correctable error statistics for each of a plurality of memory pages, wherein the correctable error statistics comprise one or more page retirement criteria, wherein the one or more page retirement criteria comprise a correctable error count, correctable error rate, or a time since a most recent correctable error;

detect a high-risk page, wherein detecting the high-risk page comprises determining whether the page retirement criteria of the high-risk page has exceeded a retirement criteria threshold;

place page information associated with the high-risk page on a retired page list, wherein the retired page list has a size corresponding to a number of spare pages stored in a reserved space of a RAM;

store identical data to data stored in the high-risk page in a spare page; and

identify, in a mapping of the plurality of memory pages, the high-risk page such that one or more references to the high-risk page in the mapping are rerouted to the spare page.