Counter-based entry invalidation for metadata previous write queue

• US 8,909,879 B2
• Filed: 06/11/2012
• Issued: 12/09/2014
• Est. Priority Date: 06/11/2012
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Bonanno, James J., Prasky, Brian R.
• Primary Examiner(s): Farrokh, Hashem
• Application Number:
  US13/493,644
• Publication Number:
  US 20130332683A1
• Time in Patent Office: 911 Days
• Field of Search: 711/156, 711/159
• US Class Current: 711/156
• CPC Class Codes: G06F 11/076 by exceeding a count or rate limit, e.g. word- or bit count limit
• CPC Class Codes: G06F 12/00 Accessing, addressing or allocating within memory systems or architectures digital input from, or digital output to record carriers, e.g. to disk storage units, G06F3/06
• CPC Class Codes: G06F 12/0802 Addressing of a memory level in which the access to the desired data or data block requires associative addressing means, e.g. caches
• CPC Class Codes: G06F 12/0891 using clearing, invalidating or resetting means
• CPC Class Codes: G06F 12/12 Replacement control
• CPC Class Codes: G06F 13/385 for adaptation of a particular data processing system to different peripheral devices

Abstract

Embodiments of the invention relate to counter-based entry invalidation for a metadata previous write queue (PWQ). An aspect of the invention includes writing an address into an entry in the metadata PWQ, the address being associated with an instance of metadata received from a pipeline and setting a valid tag associated with the entry in the metadata PWQ to valid. Another aspect of the invention includes initializing a counter to zero and incrementing the counter based on receiving a count signal from the pipeline until the counter is equal to a threshold. Yet another aspect of the invention includes setting the valid tag to invalid based on the counter being equal to the threshold.

Claims

1. A computer program product for implementing counter-based entry invalidation for a metadata previous write queue (PWQ), the computer program product comprising:

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

writing, by a processor, an address into an entry in the metadata PWQ, the address being associated with an instance of metadata received from a pipeline;

setting a valid tag associated with the entry in the metadata PWQ to valid;

initializing a counter to zero;

incrementing the counter based on receiving a count signal from the pipeline until the counter is equal to a threshold; and

setting the valid tag to invalid based on the counter being equal to the threshold.

2. The computer program product of claim 1, wherein the metadata PWQ comprises a plurality of entries, each of the plurality of entries having an associated respective valid tag, and wherein setting the valid tag to invalid further comprises setting each of the plurality of valid tags associated with the plurality of entries to invalid.

3. The computer program product of claim 1, wherein the metadata PWQ comprises a plurality of entries, and further comprising a plurality of counters, each of the plurality of counters being associated with a respective entry of the plurality of entries.

4. The computer program product of claim 3, wherein initializing a counter to zero comprises initializing a respective counter of the plurality of counters associated with the entry to zero based on writing an address into the entry.

5. The computer program product of claim 3, further comprising incrementing each of the plurality of counters simultaneously based on the count signal from the pipeline.

6. The computer program product of claim 3, further comprising a plurality of thresholds, each threshold being associated with a respective counter of the plurality of counters, and wherein determining whether the counter is equal to the threshold comprises determining whether the counter is equal to counter'"'"'s respective threshold.

7. The computer program product of claim 6, wherein a value of a threshold is determined based on one of a number of operations associated with the address that are in the pipeline at the time of writing the address into the entry in the metadata PWQ, and a total number of operations in the pipeline at the time of writing the address into the entry in the metadata PWQ.

8. The computer program product of claim 1, further comprising:

receiving an address and an instance of metadata for writing into a metadata store associated with the metadata PWQ;

determining whether a matching entry for the address exists in the metadata PWQ;

determining whether a valid tag in the matching entry is set to valid based on determining that the matching entry for the address exists in the metadata PWQ; and

avoiding writing the address and the instance of metadata into the metadata store based on determining that the valid tag in the matching entry is set to valid.

9. A computer implemented method for counter-based entry invalidation for a metadata previous write queue (PWQ), the method comprising:

writing, by a processor, an address into an entry in the metadata PWQ, the address being associated with an instance of metadata received from a pipeline;

setting a valid tag associated with the entry in the metadata PWQ to valid;

initializing a counter to zero;

incrementing the counter based on receiving a count signal from the pipeline until the counter is equal to a threshold; and

setting the valid tag to invalid based on the counter being equal to the threshold.

10. The computer implemented method of claim 9, wherein the metadata PWQ comprises a plurality of entries, each of the plurality of entries having an associated respective valid tag, and wherein setting the valid tag to invalid further comprises setting each of the plurality of valid tags associated with the plurality of entries to invalid.

11. The computer implemented method of claim 9, wherein the metadata PWQ comprises a plurality of entries, and further comprising a plurality of counters, each of the plurality of counters being associated with a respective entry of the plurality of entries.

12. The computer implemented method of claim 11, wherein initializing a counter to zero comprises initializing a respective counter of the plurality of counters associated with the entry to zero based on writing an address into the entry.

13. The computer implemented method of claim 11, further comprising incrementing each of the plurality of counters simultaneously based on the count signal from the pipeline.

14. The computer implemented method of claim 11, further comprising a plurality of thresholds, each threshold being associated with a respective counter of the plurality of counters, and wherein determining whether the counter is equal to the threshold comprises determining whether the counter is equal to counter'"'"'s respective threshold.

15. The computer implemented method of claim 14, wherein a value of a threshold is determined based on one of a number of operations associated with the address that are in the pipeline at the time of writing the address into the entry in the metadata PWQ, and a total number of operations in the pipeline at the time of writing the address into the entry in the metadata PWQ.