git: 297394e995e5 - main - igc(4): document adaptive interrupt moderation

The branch main has been updated by kbowling:

URL: https://cgit.FreeBSD.org/src/commit/?id=297394e995e5ea1ea9bc85e609ca116255d51e97

commit 297394e995e5ea1ea9bc85e609ca116255d51e97
Author:     Kevin Bowling <kbowling@FreeBSD.org>
AuthorDate: 2026-07-26 00:10:38 +0000
Commit:     Kevin Bowling <kbowling@FreeBSD.org>
CommitDate: 2026-07-26 01:00:03 +0000

    igc(4): document adaptive interrupt moderation
    
    Describe the disabled, adaptive, and low-latency settings and their
    interrupt-rate tradeoffs.
    
    MFC after:      1 week
---
 share/man/man4/igc.4 | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/share/man/man4/igc.4 b/share/man/man4/igc.4
index 757c7dd4510d..3b92472e8355 100644
--- a/share/man/man4/igc.4
+++ b/share/man/man4/igc.4
@@ -125,6 +125,20 @@ Default 1 (disabled).
 .It Va hw.igc.max_interrupt_rate
 Maximum device interrupts per second.
 The default is 8000.
+This is the rate used when adaptive interrupt moderation is disabled, and
+the fallback when it has no usable measurement.
+.It Va hw.igc.enable_aim
+Adaptive interrupt moderation.
+The interrupt rate is derived from the average size of the packets seen
+since the previous interrupt, so that bulk traffic is coalesced while small
+packet traffic keeps its latency.
+A value of 0 disables it and pins the rate to
+.Va hw.igc.max_interrupt_rate ,
+1 selects the normal range, and 2 selects the low-latency range.
+The default value is 1.
+Setting 2 raises the interrupt rate substantially on small packet workloads
+and is rarely a win; prefer the default unless latency has been measured to
+matter more than the additional interrupt load.
 .El
 .Sh DIAGNOSTICS
 .Bl -diag