ADLINK Technology AdvancedMC AMC-8100, User Manual

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BIOS Features 39
AMC-8100
5.5.5 Interrupt Coalescing
The LSI host adapters can complete multiple I/O requests per host
interrupt. Interrupt coalescing is used to reduce CPU interrupts by
pooling multiple disk command completions (I/O) into one inter-
rupt. This feature may be enabled or disabled.
LSI has performed significant testing under multiple I/O conditions,
and has determined that interrupt coalescing can be very valuable
for small transfer lengths or random, transaction-oriented I/O
workloads. For this type of workload, LSI recommends that the
Interrupt Coalescing values be set to a queue depth of 9, with a
timeout of 1280 µs (0x500). This means that the host is interrupted
only once for 9 I/Os processed by the chip, unless 1280 µs have
passed since the host was last interrupted. If the workload is of a
large transfer length and sequential, LSI recommends that inter-
rupt coalescing be disabled, to prevent performance degradation.
Although LSI has determined that these settings are optimal for a
wide variety of situations, your own I/O load may benefit from a
deeper queue or a longer timeout. LSI provides a mechanism to
modify these values and write them to the nonvolatile EEPROM
on the adapter.
Select the port or adapter shown (use the port name your system
assigns):
ok select /pci@8,700000/IntraServer,fc@1
Then enter commands as shown in the following example:
ok show-interrupt-coalescing
Interrupt coalescing timeout is 500 (1280 decimal)
microseconds
Interrupt coalescing depth is 9 (9 decimal)
ok set-interrupt-coalescing
usage is <timeout><depth> set-interrupt-coalescing
NOTE: NOTE:
The OpenBoot BIOS provides help when you enter a com-
mand that does contain the proper arguments. In this case,
OpenBoot responds with: