Dynamic map pre-fetching for improved sequential reads of a solid-state media
Described embodiments provide a solid-state drive (SSD) including a media controller and a solid-state media. A control processor of the media controller determines a logical address, a transfer size, and map data based on the logical address and transfer size, associated with a read request received from a host device. Based on the logical address and a sequential zone defined based on one or more previous read requests, the control processor determines whether the received read request is a sequential read. A map data pre-fetch size is adjusted based on the transfer size of the received read request and whether the received read request is a sequential read. A corresponding portion of the map data is transferred from the solid-state media to a map cache coupled to the control processor, the transferred portion having a size equal to the adjusted map data pre-fetch size.
1. A solid-state drive (SSD) comprising a media controller and a solid-state media, the media controller in communication with a host device, the media controller comprising:
a map cache;
a control processor coupled to the map cache and configured to:
determine a logical address, a transfer size, and map data based on the determined logical address and transfer size, associated with a received current read request from the host device;
determine, based on the determined logical address and a sequential zone defined based on one or more previous read requests, whether the current read request is a sequential read request;
adjust a map data pre-fetch size based on the transfer size of the current read request and whether the current read request is a sequential read request by adding the transfer size of the current read request with an aggregate transfer size of the one or more previous read requests when the current read request is a sequential read request;
transfer a corresponding portion of the map data from the solid-state media to the map cache, the transferred portion having a size equal to the adjusted map data pre-fetch size;
determine, based on the corresponding map data, one or more media addresses of the solid-state media associated with the determined logical address and transfer size; and
transfer user data from the one or more determined media addresses of the solid-state media to the host device.
2. The media controller of claim 1 , wherein adjusting the map data pre-fetch size further includes
set the map data pre-fetch size equal to the aggregate transfer size, to reduce a number of map data transfers between the solid-state media and the map cache to process the sequential read requests.
3. The media controller of claim 2 , wherein, by setting the map data pre-fetch size equal to the aggregate transfer size, the media controller is configured to achieve at least a 10% data throughput increase.
4. The media controller of claim 1 , wherein to adjust the map data pre-fetch size, the control processor is configured to:
when the current read request is a non-sequential read request:
set the map data pre-fetch size equal to a predefined size based on the transfer size of the current read request to reduce an amount of map data transferred between the solid-state media and the map cache to process the current read request.
5. The media controller of claim 4 , wherein the predefined size comprises a smallest amount of data needed to process the entire transfer size of the current read request.
6. The media controller of claim 1 , wherein, to transfer map data including the corresponding map data from the solid-state media to a map cache of the media controller, the media controller is configured to:
determine, based on the at least one logical address and transfer size, whether the corresponding map data is stored in the map cache;
if the required map data is stored in the map cache, the map cache is configured to return a cache index of the map cache entry storing the required map data to the control processor.
7. The media controller of claim 6 , wherein, if the corresponding map data is not stored in the map cache, the control processor is configured to:
allocate a number of entries in the map cache to store the corresponding map data, the number of allocated entries based on the adjusted map data pre-fetch size;
transfer the map data including the corresponding map data from a logical unit of the solid-state media to a local cache of the solid-state media, the transfer having a size equal to the adjusted map data pre-fetch size; and
transfer the map data including the corresponding map data from the local cache of the solid-state media to the map cache of the media controller, the transfer having a size equal to the adjusted map data pre-fetch size.
8. The media controller of claim 1 , wherein, to transfer user data from the one or more media addresses of the solid-state media to the host device, the media controller is configured to:
transfer the user data from the media addresses in a logical unit of the solid-state media to a local cache of the solid-state media;
transfer the user data from the local cache of the solid-state media to a buffer of the media controller; and
form one or more host protocol packets to transfer the user data from the buffer to the host device over a communication link operating in accordance with the host protocol.
9. The media controller of claim 8 , wherein the media controller is configured to:
when all of the user data of a read request is transferred to the host device, report completion of the read request to the host device.
10. The media controller of claim 1 , wherein the control processor is configured to:
determine whether a subsequent read request is received from the host device; and
process the subsequent read request as the current read request.
11. The media controller of claim 1 , wherein the map data comprises a multi-level map having a plurality of leaf-level map pages, the plurality of leaf-level map pages stored in the solid-state media, each leaf-level map page comprising a plurality of map entries, each entry associated with one or more physical addresses of the solid-state media.
12. The media controller of claim 1 , wherein the map data comprises a multi-level map, the multi-level map comprising:
a second-level map having a plurality of second-level map pages, each of the second-level map pages having a plurality of entries, each entry configured to store a physical address of the solid state media; and
a first-level map having a plurality of entries, each entry associated with a second-level map page, the first-level map configured to associate the at least one logical address and address range to at least one of the second-level map pages.
13. The media controller of claim 1 , wherein the sequential zone is defined based on a logical address range of the one or more previous read requests, and the current read request is within the sequential zone if the determined logical address of the current read request is within the logical address range of the one or more previous read requests.
14. The media controller of claim 1 , wherein the media controller is implemented as a System-on-Chip (SoC).
15. A method of processing, by a solid-state drive (SSD) comprising a media controller and a solid-state media, a request received from a host device, the method comprising:
determining, by a control processor of the media controller, a logical address, a transfer size, and map data based on the determined logical address and transfer size, associated with a received current read request from the host device;
determining, by the control processor, based on the determined logical address and a sequential zone defined based on one or more previous read requests, whether the current read request is a sequential read request;
adjusting, by the control processor, a map data pre-fetch size based on the transfer size of the current read request and whether the current read request is a sequential read request by adding the transfer size of the current read request with an aggregate transfer size of the one or more previous read requests when the current read request is a sequential read request;
transferring a corresponding portion of the map data from the solid-state media to a map cache coupled to the control processor, the transferred portion having a size equal to the adjusted map data pre-fetch size;
determining, based on the corresponding map data, one or more media addresses of the solid-state media associated with the determined logical address and transfer size; and
transferring user data from the one or more determined media addresses of the solid-state media to the host device.
16. The method of claim 15 , wherein adjusting the map data pre-fetch size further comprises:
setting the map data pre-fetch size equal to the aggregate transfer size, to reduce a number of map data transfers between the solid-state media and the map cache to process the sequential read requests.
17. The method of claim 16 , wherein, by setting the map data pre-fetch size equal to the aggregate transfer size, data throughput is increased at least 10%.
18. The method of claim 15 , wherein adjusting the map data pre-fetch size comprises:
when the current read request is a non-sequential read request:
setting the map data pre-fetch size equal to a predefined size based on the transfer size of the current read request to reduce an amount of map data transferred between the solid-state media and the map cache to process the current read request.
19. The method of claim 18 , wherein the predefined size comprises a smallest amount of data needed to process the entire transfer size of the current read request.
20. The method of claim 15 , wherein, transferring map data including the corresponding map data from the solid-state media to a map cache of the media controller comprises:
determining, based on the at least one logical address and transfer size, whether the corresponding map data is stored in the map cache;
if the required map data is stored in the map cache, returning, by the map cache, a cache index of the map cache entry storing the required map data to the control processor.
21. The method of claim 20 , wherein, if the corresponding map data is not stored in the map cache, the method comprises:
allocating a number of entries in the map cache to store the corresponding map data, the number of allocated entries based on the adjusted map data pre-fetch size;
transferring the map data including the corresponding map data from a logical unit of the solid-state media to a local cache of the solid-state media, the transfer having a size equal to the adjusted map data pre-fetch size; and
transferring the map data including the corresponding map data from the local cache of the solid-state media to the map cache of the media controller, the transfer having a size equal to the adjusted map data pre-fetch size.
22. The method of claim 15 , wherein, transferring user data from the one or more determined media addresses of the solid-state media to the host device comprises:
transferring the user data from the determined media addresses in a logical unit of the solid-state media to a local cache of the solid-state media;
transferring the user data from the local cache of the solid-state media to a buffer of the media controller; and
forming one or more host protocol packets to transfer the user data from the buffer to the host device over a communication link operating in accordance with the host protocol.
23. The method of claim 22 , comprising:
when all of the user data of a read request is transferred to the host device, reporting completion of the read request to the host device.
24. The method of claim 15 , comprising:
determining whether a subsequent read request is received from the host device; and
processing the subsequent read request as the current read request.
25. The method of claim 15 , wherein the map data comprises a multi-level map having a plurality of leaf-level map pages, the plurality of leaf-level map pages stored in the solid-state media, each leaf-level map page comprising a plurality of map entries, each entry associated with one or more physical addresses of the solid-state media.
26. The method of claim 15 , wherein the map data comprises a multi-level map, the multi-level map comprising:
a second-level map having a plurality of second-level map pages, each of the second-level map pages having a plurality of entries, each entry configured to store a physical address of the solid state media; and
a first-level map having a plurality of entries, each entry associated with a second-level map page, the first-level map configured to associate the at least one logical address and address range to at least one of the second-level map pages.
27. The method of claim 15 , comprising:
defining the sequential zone based on a logical address range of the one or more previous read requests, and determining that the current read request is within the sequential zone if the determined logical address of the current read request is within the logical address range of the one or more previous read requests.
28. A non-transitory machine-readable storage medium, having encoded thereon program code, wherein, when the program code is executed by a machine, the machine implements a method of of processing, by a solid-state drive (SSD) comprising a media controller and a solid-state media, a request received from a host device, the method comprising:
determining, by a control processor of the media controller, a logical address, a transfer size, and map data based on the determined logical address and transfer size, associated with a received current read request from the host device;
determining, by the control processor, based on the determined logical address and a sequential zone defined based on one or more previous read requests, whether the current read request is a sequential read request;
adjusting, by the control processor, a map data pre-fetch size based on the transfer size of the current read request and whether the current read request is a sequential read request by adding the transfer size of the current read request with an aggregate transfer size of the one or more previous read requests when the current read request is a sequential read request;
transferring a corresponding portion of the map data from the solid-state media to a map cache coupled to the control processor, the transferred portion having a size equal to the adjusted map data pre-fetch size;
determining, based on the corresponding map data, one or more media addresses of the solid-state media associated with the determined logical address and transfer size; and
transferring user data from the one or more determined media addresses of the solid-state media to the host device.