Solarflare Solarflare XtremeScale series, User Manual, Page: 238 / 400

Solarflare Server Adapter User Guide
Solarflare Adapters on Windows
Issue 20 © Solarflare Communications 2017 231
Solarflare adapters, by default, use an adaptive algorithm where the interrupt
moderation delay is automatically adjusted between zero (no interrupt moderation)
and 60 microseconds. The adaptive algorithm detects latency sensitive traffic
patterns and adjusts the interrupt moderation interval accordingly.
Interrupt moderation settings are critical for tuning adapter latency :
• Disabling the adaptive algorithm will:
‐ reduce jitter
‐ allow setting the moderation interval as required to suit conditions.
• Increasing the interrupt moderation interval will:
‐ generate less interrupts
‐ reduce CPU utilization (because there are less interrupts to process)
‐ increase latency
‐ improve peak throughput.
• Decreasing the interrupt moderation interval will:
‐ generate more interrupts
‐ increase CPU utilization (because there are more interrupts to process)
‐ decrease latency
‐ reduce peak throughput.
• Turning off interrupt moderation will:
‐ generate the most interrupts
‐ give the highest CPU utilization
‐ give the lowest latency
‐ give the biggest reduction in peak throughput.
For many transaction request ‐ response type network applications, the benefit of
reduced latency to overall application performance can be considerable. Such
benefits typically outweigh the cost of increased CPU utilization. It is recommended
that:
• Interrupt moderation is disabled for applications that require best latency and
jitter performance, such as market data handling.
• Interrupt moderation is enabled for high throughput single (or few) connection
TCP streaming applications, such as iSCSI.
Interrupt moderation can be disabled or enabled using the Interrupt Moderation
setting in the Network Adapter’s Advanced Properties Page. The interrupt
moderation time value can also be configured from the Network Adapter’s
Advanced Properties Page.
NOTE: The performance benefits of Receive Segment Coalescing and Large Receive
Offload are limited if interrupt moderation is disabled. See Receive Segment
Coalescing (RSC) on page 232 and Large Receive Offload (LRO) on page 233 .