# US 2014/0208036 A1 · Performing staging or destaging based on the number of waiting discard scans

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- Number: US 2014/0208036 A1
- Document ID: US20140208036A1
- Status: Published application
- Kind: A1
- Application number: 14/073,612
- Filed: 2013-11-06
- Published: 2014-07-24
- Earliest claimed: 2013-01-22
- Assignees: International Business Machines Corporation
- Applicants: International Business Machines Corporation
- Inventors: Michael T. Benhase; Lokesh M. Gupta; Matthew J. Kalos
- Web page: https://patentgrep.com/patent/US20140208036A1

## CPC

- G06F 12/0828: {with concurrent directory accessing, i.e. handling multiple concurrent coherency transactions}
- G06F 12/0804: with main memory updating (G06F12/0806 takes precedence)
- G06F 12/0868: Data transfer between cache memory and other subsystems, e.g. storage devices or host systems
- G06F 12/121: using replacement algorithms
- G06F 2212/604: Details relating to cache allocation
- G06F 2212/622: State-only directory, i.e. not recording identity of sharing or owning nodes
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)

## Abstract

A controller receives a request to perform staging or destaging operations with respect to an area of a cache. A determination is made as to whether more than a threshold number of discard scans are waiting to be performed. The controller avoids satisfying the request to perform the staging or the destaging operations or a read hit with respect to the area of the cache, in response to determining that more than the threshold number of discard scans are waiting to be performed.

## Claims

### Claim 1

A method, comprising:
receiving, by a controller, a request to perform staging or destaging operations with respect to an area of a cache;
determining whether more than a threshold number of discard scans are waiting to be performed; and
in response to determining that more than the threshold number of discard scans are waiting to be performed, avoiding satisfying the request to perform the staging or the destaging operations or a read hit with respect to the area of the cache.

### Claim 2 (depends on 1)

The method of claim 1, wherein the threshold number is five or more.

### Claim 3 (depends on 1)

The method of claim 1, the method further comprising:
in response to determining that no more than the threshold number of discard scans are waiting to be performed, satisfying the request to perform the staging or the destaging operations or the read hit with respect to the area of the cache.

### Claim 4 (depends on 1)

The method of claim 1, wherein the cache is a flash cache and discard scans are performed asynchronously to release space in the flash cache.

### Claim 5 (depends on 1)

The method of claim 1, wherein the area of the cache corresponds to an extent, a track, a volume, a logical subsystem or any other representation of storage.

### Claim at position 6

6-20. (canceled)