Solarflare
Server
Adapter
User
Guide
Solarflare
Adapters
on
Linux
Issue
20
©
Solarflare
Communications
2017
117
Busy
poll
If
the
kernel
supports
the
busy
poll
features
(Linux
3.11
or
later),
and
minimum
latency
is
the
main
consideration,
Solarflare
recommend
that
the
busy_poll
socket
options
should
be
enabled
with
a
value
of
50
microseconds
as
follows:
sysctl
net.core.busy_poll=50
&&
sysctl
net.core.busy_read=50
Only
sockets
having
a
non
‐
zero
value
for
SO_BUSY_POLL
will
be
polled,
so
the
user
should
do
one
of
the
following:
•
set
the
poll
timeout
with
the
global
busy_
read
option,
as
shown
above,
•
set
the
per
‐
socket
SO_BUSY_POLL
socket
option
on
selected
sockets.
Setting
busy_read
also
sets
the
default
value
for
the
SO_BUSY_POLL
option.
Memory
bandwidth
Many
chipsets
use
multiple
channels
to
access
main
system
memory.
Maximum
memory
performance
is
only
achieved
when
the
chipset
can
make
use
of
all
channels
simultaneously.
This
should
be
taken
into
account
when
selecting
the
number
of
memory
modules
(DIMMs)
to
populate
in
the
server.
For
optimal
memory
bandwidth
in
the
system,
it
is
likely
that:
•
all
DIMM
slots
should
be
populated
•
all
NUMA
nodes
should
have
memory
installed.
Please
consult
the
motherboard
documentation
for
details.
Intel®
QuickData
/
NetDMA
On
systems
that
support
Intel
I/OAT
(I/O
Acceleration
Technology)
features
such
as
QuickData
(a.k.a
NetDMA),
Solarflare
recommend
that
these
are
enabled
as
they
are
rarely
detrimental
to
performance.
Using
Intel®
QuickData
Technology
allows
data
copies
to
be
performed
by
the
system
and
not
the
operating
system.
This
enables
data
to
move
more
efficiently
through
the
server
and
provide
fast,
scalable,
and
reliable
throughput.
Enabling
QuickData
•
On
some
systems
the
hardware
associated
with
QuickData
must
first
be
enabled
(once
only)
in
the
BIOS
•
Load
the
QuickData
drivers
with
modprobe
ioatdma
Server
Motherboard,
Server
BIOS,
Chipset
Drivers
Tuning
or
enabling
other
system
capabilities
may
further
enhance
adapter
performance.
Readers
should
consult
their
server
user
guide.
Possible
opportunities
include
tuning
PCIe
memory
controller
(PCIe
Latency
Timer
setting
available
in
some
BIOS
versions).