Dell Emulex Family of Adapters - Manual (Page 965)

Emulex Drivers Version 10.2 for Linux User Manual P010081-01A Rev. A
Appendix A. iSCSI Driver
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alias eth0 tg3
alias scsi_hostadapter ata_piix
alias scsi_hostadapter1 usb-storage
alias scsi_hostadapter2 be2iscsi
options be2iscsi eto=0 ldto=0 large_io=512
alias eth1 be2net
alias eth2 be2net
After adding the options line, save the file, and then rebuild initrd.
Configuring the im_policy Parameter
The interrupt moderation policy setting (im_policy parameter) controls the rate of
interrupts for the OneConnect adapter. Table A-2 defines the available im_policy
settings.
By default, the driver implements an interrupt moderation scheme that is based on the
I/O load and the interrupt rate. Changing the interrupt moderation policy setting
should be based on the initiator system configuration, the number of connected iSCSI
targets, the I/O load, and the throughput and latency offered by these iSCSI targets.
The default Moderate setting (im_policy = 2) varies the interrupt rate between 3500 to
10000 interrupts per second. While the Moderate setting may work for most
configurations, there are instances when the setting may need to be altered.
On systems capable of sustaining a higher interrupt rate and when a few number of
targets are connected (up to 8), the Aggressive setting (im_policy = 1) results in lower
latency and higher values of I/O operations per second (IOPs). However, this higher
interrupt rate could also result in system stalls and freezes, especially during higher
values of queue depth and smaller sized I/O requests.
In a configuration that involves a large number of iSCSI targets (more than 32 or 64)
and higher values of queue depth, the Conservative (im_policy = 3) or Very
Conservative (im_policy = 4) setting may be more desirable. Though these settings
increase the latency of an I/O request, the lowered interrupt rate may allow the system
to be functional under a high load.
For example, to manually set the im_policy parameter for the highest interrupt rate
(Aggressive), type
insmod be2iscsi.ko im_policy=1
Table A-2 Interrupt Moderation Policy (im_policy) Settings
im_policy Value Setting Type Description
0 Disabled Interrupt moderation algorithm is turned off in the driver.
1 Aggressive Highest interrupt rate among available settings.
2 Moderate Default value; The interrupt rate varies between 3500 to
10000 interrupts per second.
3 Conservative Lower interrupt rate than Moderate.
4 Very conservative The minimum interrupt rate among available settings.