Information processing apparatus, storage device, and method performed by host system
An information processing apparatus communicates with a storage device and includes a serial interface configured to support plural link rates, and a controller. The controller retrieves from the storage device via the serial interface information indicating a relationship between maximum power consumption and power consumption efficiency value for each link rate in a first power throttling mode that gives priority to performance and a second power throttling mode that gives priority to reduction of peak power, the power consumption efficiency value being a value that corresponds to the number of I/Os per watt, select the first or the second power throttling mode based on the retrieved information and a mode specified from one of three modes, and instruct the storage device to limit power consumption based on the selected power throttling mode. The three modes include a first mode that gives priority to performance, a second mode that gives priority to reduction of power consumption, and a third mode that gives priority to reduction of peak power.
1. A storage device configured to communicate with a host system, the device comprising:
a serial interface configured to support a plurality of link rates;
a memory that stores information indicating a relationship between a maximum power consumption and a power consumption efficiency value for each link rate in first and second power throttling modes supported by the storage device, the first power throttling mode giving priority to performance of the storage device, the second power throttling mode giving priority to reduction of peak power of the storage device, the power consumption efficiency value being a value that corresponds to the number of I/Os per watt; and
a controller configured to:
receive from the host system via the serial interface an instruction to change a power throttling mode to one of the first and second throttling modes, which is selected by the host system based on the information and a user preference for performance of the host system, the user preference being one of:
a first mode that gives priority to performance of the host system,
a second mode that gives priority to reduction of power consumption of the host system, and
a third mode that gives priority to reduction of peak power of the host system; and
limit the maximum power consumption of the storage device based on the instruction received from the host system,
wherein the controller is further configured to:
store default capability information indicating the link rates supported by the storage device in a plurality of bits,
mask bits in the plurality of bits that do not correspond to a range of link rates that starts at a minimum link rate of the storage device and ends at a maximum link rate specified by the host system, and
transmit to the host system the masked plurality of bits.
2. The storage device according to claim 1 ,
wherein the user preference is specified by a user of the host system.
3. The storage device according to claim 2 ,
wherein the controller is configured to:
receive link rate specification information specifying a link rate suitable for the selected power throttling mode and determined by the host system based on the user preference specified by the user and the information; and
limit the maximum power consumption of the storage device based on the specified link rate and the selected power throttling mode.
4. The storage device according to claim 1 ,
wherein the controller is configured to transmit the masked plurality of bits when establishing a link with the host system.
5. The storage device according to claim 1 ,
wherein the controller is configured to:
insert a start bit of “1” to the masked plurality of bits;
determine whether a total number of bits of “1” included in the masked plurality of bits is even or odd; and
when the total number of bits is odd, add a parity bit of “1” to the masked plurality of bits.
6. The storage device according to claim 5 ,
wherein the controller is configured to:
determine whether or not frequency spreading of a signal is performed before determining whether the total number of bits set to “1” is even or odd; and
when the frequency spreading is not performed, update the first bit group by masking a bit indicating that the frequency spreading is performed.