Reducing delay of command completion due to overlap condition
View Patent ↗Method and apparatus for transferring data between a host device and a data storage device having a first memory space and a second memory space. The host issues access commands to store and retrieve data. The device stores commands in the first memory space pending transfer to the second memory space. An interface circuit evaluates relative proximity of first and second sets of LBAs associated with pending first and second commands, and delays promotion of later pending commands in front of earlier pending commands during an overlap condition. If the overlap is caused by performance enhancing features (PEF) the PEFs are disabled so the commands can be scheduled for disc access. Indicators are set in the commands to signal that a PEF has caused the overlap and that PEF can be disabled. Values are added to indicators in the commands such that the PEFs can be modified and avoid overlaps.
1. An apparatus comprising an interface circuit that processes commands to transfer data between a host device and a data storage medium, wherein the interface circuit selectively employs a performance enhancing feature such that, during the processing of a read command, nonrequested data are stored in an intermediate memory location when the performance enhancing feature is enabled, and wherein the interface circuit disables the performance enhancing feature in response to a potential overlap conflict detected between first and second commands such that, during the processing of a subsequent read command, nonrequested data are not stored in an intermediate memory location while the performance enhancing feature is disabled.
2. The apparatus of claim 1 , wherein the interface circuit further executes a sort strategy on the first and second commands after the performance enhancing feature is disabled and executes said commands in an order determined by said sort strategy.
3. The apparatus of claim 1 , wherein the interface circuit employs a notifier in conjunction with the first and second commands which provides a status regarding whether the performance enhancing feature is enabled or disabled for each said command.
4. An apparatus comprising an interface circuit that processes commands to transfer data between a host device and a data storage medium, wherein the interface circuit selectively employs a performance enhancing feature such that, during the processing of a read command, nonrequested data are stored in an intermediate memory location when the performance enhancing feature is enabled, and wherein the interface circuit modifies operation of the performance enhancing feature to reduce the amount of nonrequested data stored in the intermediate memory location to avoid a potential overlap conflict between a first command and a second command.
5. The apparatus of claim 4 , wherein the interface circuit further executes a sort strategy on the first and second commands after the performance enhancing feature is modified and executes said commands in an order determined by said sort strategy.
6. The apparatus of claim 4 , wherein the interface circuit employs a notifier in conjunction with the first and second commands which provides a status regarding whether the performance enhancing feature is modified for each said command.
7. The apparatus of claim 6 , wherein the notifier includes an adjustment value by which the nonrequested value is reduced to avoid the potential overlap conflict.
8. A method comprising:
enabling a performance enhancing feature that retrieves nonrequested data from a second memory space and places that data in a first memory space;
receiving first and second commands to transfer data between the second memory space and a host computer; and
disabling the performance enhancing feature when a potential overlap conflict exists between a first set of data sectors associated with the first command and a second set of data sectors associated with the second command so that nonreguested data are not placed into the first memory space while the performance enhancing feature is disabled.
9. The method of claim 8 , further comprising steps of executing a sort strategy on the first and second commands after the performance enhancing feature is disabled and executing said commands in an order determined by said sort strategy.
10. The method of claim 8 , wherein the disabling step comprises employing a notifier with the first and second commands which provides a status regarding whether the performance enhancing feature is disabled for each said command.
11. The method of claim 8 , wherein the enabling step comprises enabling a plurality of performance enhancing features, and wherein the notifier comprises a bit for each performance enhancing feature.
12. The method of claim 8 , wherein the first set of data comprises a first range of data sectors to which data are to be written or from which data are to be read in accordance with the first command plus a second range of data sectors adjacent the first range associated with the operation of the performance enhancing feature.
13. A method comprising:
enabling a performance enhancing feature that retrieves nonrequested data from a second memory space and places that data in a first memory space;
receiving first and second commands to transfer data between the second memory space and a host computer; and
modifying operation of the performance enhancing feature to reduce the amount of nonrequested data stored in the first memory space to avoid a potential overlap conflict between a first set of data associated with the first command and a second set of data associated with the second command.
14. The method of claim 13 , further comprising steps of executing a sort strategy on the first and second commands after the performance enhancing feature is modified and executing said commands in an order determined by said sort strategy.
15. The method of claim 13 , wherein the disabling step comprises employing a notifier with the first and second commands which provides a status regarding whether the performance enhancing feature is modified for each said command.
16. The method of claim 15 , wherein the notifier of the disabling step includes an adjustment value by which the nonrequested value is reduced to avoid the potential overlap conflict.
17. The method of claim 13 , wherein the first set of data comprises a first range of data sectors to which data are to be written or from which data are to be read in accordance with the first command plus a second range of data sectors adjacent the first range associated with the operation of the performance enhancing feature.