https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=236067
Bug ID: 236067
Summary: [em] Intel 82574L can not turn off flow control
Product: Base System
Version: CURRENT
Hardware: amd64
OS: Any
Status: New
Severity: Affects Only Me
Priority: ---
Component: kern
Assignee: [email protected]
Reporter: [email protected]
I have two systems with 82574L NICs.
One, name it G (for "generator"), is powerful enough to saturate almost 1G
links with small packets (more than 1100Kpps).
Other, name it DUT is underpowered and can not process such packet rate.
Both G and dut have "set dev.em.0.fc=0".
G try to generate traffic to DUT's MAC with netmap & pkt-gen. If G and DUT are
connected (no matter how: with direct patchcord or via dedicated switch) G
could generate only as much packets as DUT could process! If I remove DUT from
dedicated switch, G generates almost-line-rate PPS. If I replace DUT with other
system with I210 NIC, G generates same high PPS even if system with I210 can
not process it.
Looks like 82574L can not turn off flow control.
Once again:
82574L -> Switch -> 82574L - pkt-gen generates PPS limited by receiver.
82574L -> 82574L - pkt-gen generates PPS limited by receiver.
82574L -> Switch -> "blackhole" (no other devices attached to switch) - pkt-gen
generates line-rate PPS.
82574L -> I210 - pkt-gen generates line-rate PPS.
82574L -> Switch -> I210 - pkt-gen generates line-rate PPS.
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