Method to increase performance of non-contiguously written sectors

• US 10,013,361 B2
• Filed: 11/13/2013
• Issued: 07/03/2018
• Est. Priority Date: 10/12/2006
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Mannenbach, David F., Nielsen, Karl A.
• Primary Examiner(s): Savla, Arpan P.
• Application Number:
  US14/078,735
• Publication Number:
  US 20140068195A1
• Time in Patent Office: 1,693 Days
• 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 12/0804 with main memory updating G06F12/0806 takes precedence
• CPC Class Codes: G06F 12/0868 Data transfer between cache memory and other subsystems, e.g. storage devices or host systems
• CPC Class Codes: G06F 12/12 Replacement control
• CPC Class Codes: G06F 12/121 using replacement algorithms
• CPC Class Codes: G06F 12/126 with special data handling, e.g. priority of data or instructions, handling errors or pinning

Abstract

A method of managing data in a cache upon a cache write operation includes determining a number of non-contiguously written sectors on a track in the cache and comparing the number with a threshold number. If the number exceeds the threshold number, a full background stage operation is issued to fill the non-contiguously written sectors with unmodified data from a storage medium and the full track is then destaged. A corresponding system includes a cache manager module operating on the storage subsystem. Upon a determination that a cache write operation on a track has taken place, the cache manager module determines a number of non-contiguously written sectors on the track, compares the number with a predetermined threshold number, issues a background stage operation to fill the non-contiguously written sectors with unmodified data from a storage medium if the number exceeds the threshold number, and then destages the full track.

Claims

1. A method for managing data in a cache, the method comprising:

receiving, by the cache, a write operation, and querying by a storage subsystem whether the write operation has completed;

upon determining the write operation has completed, identifying one or more non-contiguously written sectors in a partially filled track left by the write operation;

determining a number of the non-contiguously written sectors on a track in the cache using a cache bit map that is maintained by the storage subsystem;

comparing the number of non-contiguously written sectors with a predetermined threshold number of non-contiguously written sectors;

when the number of non-contiguously written sectors on the track exceeds the predetermined threshold of non-contiguously written sectors, performing a full background stage operation to fill the one or more non-contiguously written sectors with unmodified data from a storage medium to create a full track such that the write operation triggers the full background stage operation upon determining the predetermined threshold number has been exceeded; and

destaging the full track to the storage medium;

wherein

the unmodified data from the storage medium is data missing from the full track of the data in the cache that constitutes the non-contiguously written sectors.

2. The method of claim 1, further including, prior to determining the number of non-contiguously written sectors, detecting that the write operation has taken place.

3. The method of claim 1, wherein the cache bit map further includes a resident bit map and a modified bit map, the resident and modified bit maps compared to determine the number of non-contiguously written sectors on the track.

4. The method of claim 1, wherein destaging the full track is performed with a single write command.

5. A system for managing data in a cache memory storage subsystem, comprising:

a cache manager module operating on the storage subsystem, wherein the cache manager module is configured for;

receiving, by the cache, a write operation, and querying by the storage subsystem whether the write operation has completed;

upon determining the write operation has completed, identifying one or more non-contiguously written sectors in a partially filled track left by the write operation;

determining a number of the non-contiguously written sectors on a track in the cache using a cache bit map that is maintained by a storage subsystem;

comparing the number of non-contiguously written sectors with a predetermined threshold number of non-contiguously written sectors;

when the number of non-contiguously written sectors on the track exceeds the predetermined threshold of non-contiguously written sectors, performing a full background stage operation to fill the one or more non-contiguously written sectors with unmodified data from a storage medium to create a full track such that the write operation triggers the full background stage operation upon determining the predetermined threshold number has been exceeded; and

destaging the full track to the storage medium;

wherein

the unmodified data from the storage medium is data missing from the full track of the data in the cache that constitutes the non-contiguously written sectors.

6. The system of claim 5, wherein the cache manager module is further configured for, prior to determining the number of non-contiguously written sectors, detecting that the write operation has taken place.

7. The system of claim 5, wherein the cache bit map further includes a resident bit map and a modified bit map, wherein the resident and modified bit maps are compared to determine the number of non-contiguously written sectors on the track.

8. The system of claim 5, wherein, when destaging the full track, the cache manager module is configured for destaging the full track with a single write command.

9. A non-transitory article of manufacture including code for managing data in a cache memory storage subsystem upon a cache write operation, wherein the code, when executed by a processor, causes the processor to:

receive, by the cache, a write operation, and query by the storage subsystem whether the write operation has completed;

upon determining the write operation has completed, identify one or more non-contiguously written sectors in a partially filled track left by the write operation;

determine a number of the non-contiguously written sectors on a track in the cache using a cache bit map that is maintained by a storage subsystem;

compare the number of non-contiguously written sectors with a predetermined threshold number of non-contiguously written sectors;

when the number of non-contiguously written sectors on the track exceeds the predetermined threshold of non-contiguously written sectors, perform a full background stage operation to fill the one or more non-contiguously written sectors with unmodified data from a storage medium to create a full track such that the write operation triggers the full background stage operation upon determining the predetermined threshold number has been exceeded; and

destage the full track to the storage medium;

wherein

the unmodified data from the storage medium is data missing from the full track of the data in the cache that constitutes the non-contiguously written sectors.

10. The article of manufacture of claim 9, further including code that causes the processor to, previous to the step of determining the number of non-contiguously written sectors on a track in the cache, detect that the write operation has taken place.

11. The article of manufacture of claim 9, wherein the cache bit map further includes a resident bit map and a modified bit map, the resident and modified bit maps compared to determine the number of non-contiguously written sectors on the track.

12. The article of manufacture of claim 9, wherein destaging the full track is performed with a single write command.