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NVME_CDW11_FEATURE_INTERRUPT_COALESCING union (nvme.h)

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Contains parameters for the Interrupt Coalescing Feature that configures the interrupt coalescing settings.

The values from this structure are used in the InterruptCoalescing field of the NVME_CDW11_FEATURES structure.

Syntax

typedef union {
  struct {
    ULONG THR : 8;
    ULONG TIME : 8;
    ULONG Reserved0 : 16;
  } DUMMYSTRUCTNAME;
  ULONG  AsUlong;
} NVME_CDW11_FEATURE_INTERRUPT_COALESCING, *PNVME_CDW11_FEATURE_INTERRUPT_COALESCING;

Members

DUMMYSTRUCTNAME

DUMMYSTRUCTNAME.THR

Indicates the recommended minimum number of completion queue entries to aggregate per interrupt vector before signaling an interrupt to the host. This is a 0’s based value. The reset value of this setting is 0h.

DUMMYSTRUCTNAME.TIME

Indicates the recommended maximum time in 100 microsecond increments that a controller may delay an interrupt due to interrupt coalescing. A value of 0h corresponds to no delay. The controller may apply this time per interrupt vector or across all interrupt vectors. The reset value of this setting is 0h.

DUMMYSTRUCTNAME.Reserved0

AsUlong

Remarks

The controller signals an interrupt when either the Aggregation Time (TIME) or the Aggregation Threshold (THR) conditions are met. If either the TIME or the THR fields are cleared to 0h, then interrupt coalescing is implicitly disabled.

The Interrupt Coalescing Feature is valid when the controller is configured for Pin Based, MSI, Multiple MSI or MSI-X interrupts. There is no requirement for the controller to persist these settings if interrupt modes are changed. It is recommended that the host re-issue this feature after changing interrupt modes.

The controller may delay an interrupt if it detects that interrupts are already being processed for this vector. Specifically, if the Completion Queue Head Doorbell register is being updated that is associated with a particular interrupt vector, then the controller has a positive indication that completion queue entries are already being processed. In this case, the aggregation time and/or the aggregation threshold may be reset/restarted upon the associated register write. This may result in interrupts being delayed indefinitely in certain workloads where the aggregation time or aggregation threshold are non-zero.

The Interrupt Coalescing Feature applies only to the I/O Submission and I/O Completion Queues. interrupts for commands that complete in error should not be coalesced.

Requirements

Requirement Value
Minimum supported client Windows 10
Header nvme.h

See also