Dell Emulex Family of Adapters - Manual (Page 587)

Emulex Drivers for Windows User Manual P010077-01A Rev. A
3. Configuration
FC/FCoE Driver Configuration
587
Server Performance with FC Drivers
I/O Coalescing
I/O Coalescing is enabled and controlled by two driver parameters: CoalesceMsCnt
and CoalesceRspCnt. The effect of I/O Coalescing depends on the CPU resources
available on the server. With I/O Coalescing turned on, interrupts are batched,
reducing the number of interrupts and maximizing the number of commands
processed with each interrupt. For heavily loaded systems, this provides better
throughput.
With I/O Coalescing turned off (the default), each I/O processes immediately, one
CPU interrupt per I/O. For systems not heavily loaded, the default provides better
throughput. The following table shows recommendations based upon the number of
I/Os per adapter.
CoalesceMsCnt
The CoalesceMsCnt parameter controls the maximum elapsed time in milliseconds that
the adapter waits before it generates a CPU interrupt. The value range is 0–63 (decimal)
or 0x0–0x3F (hex). The default is 0 and disables I/O Coalescing.
CoalesceRspCnt
The CoalesceRspCnt parameter controls the maximum number of responses to batch
before an interrupt generates. If CoalesceRspCnt expires, an interrupt generates for all
responses collected up to that point. With CoalesceRspCnt set to less than 2, response
coalescing is disabled and an interrupt triggers for each response. The value range for
CoalesceRspCnt is 1–255 (decimal) or 0x1–0xFF (hex). The default value is 8.
TraceBufSiz=n TraceBufSiz sets the size in bytes for the internal
driver trace buffer. The internal driver trace
buffer acts as an internal log of the driver's
activity.
Value: 250,000–2,000,000 or 0x3D090–0x1E8480
(hex).
Default = 250,000 (0x3D090) Reboot
Table 3-1 Storport Miniport Driver Parameters (Continued)
Parameter Definitions
Activation
Requirement
Adapter/Protocol
Table 3-2 Recommended Settings for I/O Coalescing
I/Os per Second Suggested CoalesceMsCnt Suggested CoalesceRspCnt
I/Os < 10000 0 8
10000 < I/Os < 18000 1 8
18000 < I/Os < 26000 1 16
1/Os > 26000 1 24