|
Using devlink-sb, we can configure 12/16 (the important 75%) of the
switch's controlling watermarks for congestion drops, and we can monitor
50% of the watermark occupancies (we can monitor the reservation
watermarks, but not the sharing watermarks, which are exposed as pool
sizes).
The following definitions can be made:
SB_BUF=0 # The devlink-sb for frame buffers
SB_REF=1 # The devlink-sb for frame references
POOL_ING=0 # The pool for ingress traffic. Both devlink-sb instances
# have one of these.
POOL_EGR=1 # The pool for egress traffic. Both devlink-sb instances
# have one of these.
Editing the hardware watermarks is done in the following way:
BUF_xxxx_I is accessed when sb=$SB_BUF and pool=$POOL_ING
REF_xxxx_I is accessed when sb=$SB_REF and pool=$POOL_ING
BUF_xxxx_E is accessed when sb=$SB_BUF and pool=$POOL_EGR
REF_xxxx_E is accessed when sb=$SB_REF and pool=$POOL_EGR
Configuring the sharing watermarks for COL_SHR(dp=0) is done implicitly
by modifying the corresponding pool size. By default, the pool size has
maximum size, so this can be skipped.
devlink sb pool set pci/0000:00:00.5 sb $SB_BUF pool $POOL_ING \
size 129840 thtype static
Since by default there is no buffer reservation, the above command has
maxed out BUF_COL_SHR_I(dp=0).
Configuring the per-port reservation watermark (P_RSRV) is done in the
following way:
devlink sb port pool set pci/0000:00:00.5/0 sb $SB_BUF \
pool $POOL_ING th 1000
The above command sets BUF_P_RSRV_I(port 0) to 1000 bytes. After this
command, the sharing watermarks are internally reconfigured with 1000
bytes less, i.e. from 129840 bytes to 128840 bytes.
Configuring the per-port-tc reservation watermarks (Q_RSRV) is done in
the following way:
for tc in {0..7}; do
devlink sb tc bind set pci/0000:00:00.5/0 sb 0 tc $tc \
type ingress pool $POOL_ING \
th 3000
done
The above command sets BUF_Q_RSRV_I(port 0, tc 0..7) to 3000 bytes.
The sharing watermarks are again reconfigured with 24000 bytes less.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
|
|
This is meant to be a gentle introduction into the world of watermarks
on ocelot. The code is placed in ocelot_devlink.c because it will be
integrated with devlink, even if it isn't right now.
My first step was intended to be to replicate the default configuration
of the congestion watermarks programatically, since they are now going
to be tuned by the user.
But after studying and understanding through trial and error how they
work, I now believe that the configuration used out of reset does not do
justice to the word "reservation", since the sum of all reservations
exceeds the total amount of resources (otherwise said, all reservations
cannot be fulfilled at the same time, which means that, contrary to the
reference manual, they don't guarantee anything).
As an example, here's a dump of the reservation watermarks for frame
buffers, for port 0 (for brevity, the ports 1-6 were omitted, but they
have the same configuration):
BUF_Q_RSRV_I(port 0, prio 0) = max 3000 bytes
BUF_Q_RSRV_I(port 0, prio 1) = max 3000 bytes
BUF_Q_RSRV_I(port 0, prio 2) = max 3000 bytes
BUF_Q_RSRV_I(port 0, prio 3) = max 3000 bytes
BUF_Q_RSRV_I(port 0, prio 4) = max 3000 bytes
BUF_Q_RSRV_I(port 0, prio 5) = max 3000 bytes
BUF_Q_RSRV_I(port 0, prio 6) = max 3000 bytes
BUF_Q_RSRV_I(port 0, prio 7) = max 3000 bytes
Otherwise said, every port-tc has an ingress reservation of 3000 bytes,
and there are 7 ports in VSC9959 Felix (6 user ports and 1 CPU port).
Concentrating only on the ingress reservations, there are, in total,
8 [traffic classes] x 7 [ports] x 3000 [bytes] = 168,000 bytes of memory
reserved on ingress.
But, surprise, Felix only has 128 KB of packet buffer in total...
A similar thing happens with Seville, which has a larger packet buffer,
but also more ports, and the default configuration is also overcommitted.
This patch disables the (apparently) bogus reservations and moves all
resources to the shared area. This way, real reservations can be set up
by the user, using devlink-sb.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
|
