Commit Graph

90 Commits

Author SHA1 Message Date
Navdeep Parhar
e25621e5ea cxgbe(4): Provide more details about the card in the sysctl MIB.
dev.t5nex.0.%desc: Chelsio T580-CR
dev.t5nex.0.hw_revision: 1
dev.t5nex.0.sn: PT13140042
dev.t5nex.0.pn: 110117150A0
dev.t5nex.0.ec: 0000000000000000
dev.t5nex.0.na: 0007432AF490
dev.t5nex.0.vpd_version: 3
dev.t5nex.0.scfg_version: 53255
dev.t5nex.0.bs_version: 1.1.0.0
dev.t5nex.0.er_version: 1.0.0.68
dev.t5nex.0.tp_version: 0.1.4.9
dev.t5nex.0.firmware_version: 1.16.2.0

Sponsored by:	Chelsio Communications
2016-08-27 00:13:41 +00:00
John Baldwin
ec55567ce6 Track the base absolute ID of ingress and egress queues.
Use this to map an absolute queue ID to a logical queue ID in interrupt
handlers.  For the regular cxgbe/cxl drivers this should be a no-op as
the base absolute ID should be zero.  VF devices have a non-zero base
absolute ID and require this change.  While here, export the absolute ID
of egress queues via a sysctl.

Reviewed by:	np
Sponsored by:	Chelsio Communications
Differential Revision:	https://reviews.freebsd.org/D7446
2016-08-09 17:49:42 +00:00
John Baldwin
a56745092c Reserve an adapter flag IS_VF to mark VF devices vs PF devices.
Sponsored by:	Chelsio Communications
2016-08-08 21:45:39 +00:00
John Baldwin
315048f2ad Store the offset of the KDOORBELL and GTS registers in the softc.
VF devices use a different register layout than PF devices.  Storing
the offset in a value in the softc allows code to be shared between the
PF and VF drivers.

Reviewed by:	np
Sponsored by:	Chelsio Communications
Differential Revision:	https://reviews.freebsd.org/D7389
2016-08-01 22:39:51 +00:00
Navdeep Parhar
671bf2b8b2 cxgbe(4): Changes to the CPL-handler registration mechanism and code
related to "shared" CPLs.

a) Combine t4_set_tcb_field and t4_set_tcb_field_rpl into a single
function.  Allow callers to direct the response to any iq.  Tidy up
set_ulp_mode_iscsi while there to use names from t4_tcb.h instead of
magic constants.

b) Remove all CPL handler tables from struct adapter.  This reduces its
size by around 2KB.  All handlers are now registered at MOD_LOAD instead
of attach or some kind of initialization/activation.  The registration
functions do not need an adapter parameter any more.

c) Add per-iq handlers to deal with CPLs whose destination cannot be
determined solely from the opcode.  There are 2 such CPLs in use right
now: SET_TCB_RPL and L2T_WRITE_RPL.  The base driver continues to send
filter and L2T_WRITEs over the mgmtq and solicits the reply on fwq.
t4_tom (including the DDP code) now uses the port's ctrlq to send
L2T_WRITEs and SET_TCB_FIELDs and solicits the reply on an ofld_rxq.
fwq and ofld_rxq have different handlers that know what kind of tid to
expect in the reply.  Update t4_write_l2e and callers to to support any
wrq/iq combination.

Approved by:	re@ (kib@)
Sponsored by:	Chelsio Communications
2016-07-05 01:29:24 +00:00
Navdeep Parhar
62291463de cxgbe(4): Merge netmap support from the ncxgbe/ncxl interfaces to the
vcxgbe/vcxl interfaces and retire the 'n' interfaces.  The main
cxgbe/cxl interfaces and tunables related to them are not affected by
any of this and will continue to operate as usual.

The driver used to create an additional 'n' interface for every
cxgbe/cxl interface if "device netmap" was in the kernel.  The 'n'
interface shared the wire with the main interface but was otherwise
autonomous (with its own MAC address, etc.).  It did not have normal
tx/rx but had a specialized netmap-only data path.  r291665 added
another set of virtual interfaces (the 'v' interfaces) to the driver.
These had normal tx/rx but no netmap support.

This revision consolidates the features of both the interfaces into the
'v' interface which now has a normal data path, TOE support, and native
netmap support.  The 'v' interfaces need to be created explicitly with
the hw.cxgbe.num_vis tunable.  This means "device netmap" will not
result in the automatic creation of any virtual interfaces.

The following tunables can be used to override the default number of
queues allocated for each 'v' interface.  nofld* = 0 will disable TOE on
the virtual interface and nnm* = 0 to will disable native netmap
support.

# number of normal NIC queues
hw.cxgbe.ntxq_vi
hw.cxgbe.nrxq_vi

# number of TOE queues
hw.cxgbe.nofldtxq_vi
hw.cxgbe.nofldrxq_vi

# number of netmap queues
hw.cxgbe.nnmtxq_vi
hw.cxgbe.nnmrxq_vi

hw.cxgbe.nnm{t,r}xq{10,1}g tunables have been removed.

--- tl;dr version ---
The workflow for netmap on cxgbe starting with FreeBSD 11 is:
1) "device netmap" in the kernel config.
2) "hw.cxgbe.num_vis=2" in loader.conf.  num_vis > 2 is ok too, you'll
end up with multiple autonomous netmap-capable interfaces for every
port.
3) "dmesg | grep vcxl | grep netmap" to verify that the interface has
netmap queues.
4) Use any of the 'v' interfaces for netmap.  pkt-gen -i vcxl<n>... .
One major improvement is that the netmap interface has a normal data
path as expected.
5) Just ignore the cxl interfaces if you want to use netmap only.  No
need to bring them up.  The vcxl interfaces are completely independent
and everything should just work.
---------------------

Approved by:	re@ (gjb@)
Relnotes:	Yes
Sponsored by:	Chelsio Communications
2016-06-23 02:53:00 +00:00
Navdeep Parhar
02f972e8f3 cxgbe(4): Add a sysctl to manage the binding of a txq to a traffic class.
Sponsored by:	Chelsio Communications
2016-06-08 14:15:29 +00:00
Navdeep Parhar
46464b95b0 cxgbe(4): Track the state of the hardware traffic schedulers in the
driver.  This works as long as everyone uses set_sched_class_params
to program them.

Sponsored by:	Chelsio Communications
2016-06-07 00:27:55 +00:00
Pedro F. Giffuni
453130d9bf sys/dev: minor spelling fixes.
Most affect comments, very few have user-visible effects.
2016-05-03 03:41:25 +00:00
John Baldwin
80f3b01958 Remove #ifdef's from various structures used in the cxgbe/cxl driver.
This provides a constant ABI and layout for these structures (especially
struct adapter) avoiding some foot shooting.

Discussed with:	np
Sponsored by:	Chelsio Communications
2016-03-31 18:36:50 +00:00
Navdeep Parhar
0f2f53efd2 cxgbe(4): Catch up with the latest list of card capabilities as reported
by the firmware.
2016-03-12 02:54:55 +00:00
Navdeep Parhar
9945ceb857 cxgbe(4): Add sysctls to display the TP microcode version and the
expansion rom version (if there's one).

trantor:~# sysctl dev.t4nex dev.t5nex | grep _version
dev.t4nex.0.firmware_version: 1.15.28.0
dev.t4nex.0.tp_version: 0.1.9.4
dev.t5nex.0.firmware_version: 1.15.28.0
dev.t5nex.0.exprom_version: 1.0.0.68
dev.t5nex.0.tp_version: 0.1.4.9
2016-03-11 03:15:17 +00:00
Navdeep Parhar
c912289045 cxgbe(4): Add general purpose routines that offer safe access to the
chip's memory windows.  Convert existing users of these windows to the
new routines.
2016-03-10 06:15:31 +00:00
Navdeep Parhar
4d131308f3 cxgbe(4): Rename regwin_lock to reg_lock. It is used to protect access
to indirect registers only.
2016-03-08 22:23:30 +00:00
Navdeep Parhar
b3500921c4 cxgbe(4): Updates to the shared routines that deal with the serial EEPROM,
flash, and VPD.

Obtained from:	Chelsio Communications
2016-03-08 07:48:55 +00:00
Navdeep Parhar
700cfba72d cxgbe(4): Overhaul the shared code that deals with the chip's TP block,
which is responsible for filtering and RSS.

Add the ability to use filters that match on PF/VF (aka "VNIC id") while
here.  This is mutually exclusive with filtering on outer VLAN tag with
Q-in-Q.

Sponsored by:	Chelsio Communications
2016-03-08 02:04:05 +00:00
Navdeep Parhar
90e7434a6d cxgbe(4): Add a struct sge_params to store per-adapter SGE parameters.
Move the code that reads all the parameters to t4_init_sge_params in the
shared code.  Use these per-adapter values instead of globals.

Sponsored by:	Chelsio Communications
2016-03-08 00:23:56 +00:00
Navdeep Parhar
d1205d093d cxgbe(4): Very basic T6 awareness. This is part of ongoing work to
update to the latest internal shared code.

- Add a chip_params structure to keep track of hardware constants for
  all generations of Terminators handled by cxgbe.
- Update t4_hw_pci_read_cfg4 to work with T6.
- Update the hardware debug sysctls (hidden within dev.<tNnex>.<n>.misc.*) to
  work with T6.  Most of the changes are in the decoders for the CIM
  logic analyzer and the MPS TCAM.
- Acquire the regwin lock around indirect register accesses.

Obtained from:	Chelsio Communications
Sponsored by:	Chelsio Communications
2016-03-04 13:11:13 +00:00
Navdeep Parhar
e8c6ba7265 cxgbe(4): Add a sysctl to retrieve the maximum speed/bandwidth supported by a
port.

dev.cxgbe.<n>.max_speed
dev.cxl.<n>.max_speed

Sponsored by:	Chelsio Communications
2016-02-25 01:10:56 +00:00
Navdeep Parhar
40bf7442fa cxgbe: catch up with the latest hardware-related definitions.
Obtained from:	Chelsio Communications
Sponsored by:	Chelsio Communications
2016-02-19 00:29:16 +00:00
Navdeep Parhar
9eb533d3b4 cxgbe(4): Updates to the base NIC driver and t4_tom to support the iSCSI
offload driver.  These changes come from projects/cxl_iscsi.
2015-12-26 00:26:02 +00:00
John Baldwin
fe2ebb7644 Add support for configuring additional virtual interfaces (VIs) on a port.
Each virtual interface has its own MAC address, queues, and statistics.
The dedicated netmap interfaces (ncxgbeX / ncxlX) were already implemented
as additional VIs on each port.  This change allows additional non-netmap
interfaces to be configured on each port.  Additional virtual interfaces
use the naming scheme vcxgbeX or vcxlX.

Additional VIs are enabled by setting the hw.cxgbe.num_vis tunable to a
value greater than 1 before loading the cxgbe(4) or cxl(4) driver.
NB: The first VI on each port is the "main" interface (cxgbeX or cxlX).

T4/T5 NICs provide a limited number of MAC addresses for each physical port.
As a result, a maximum of six VIs can be configured on each port (including
the "main" interface and the netmap interface when netmap is enabled).

One user-visible result is that when netmap is enabled, packets received
or transmitted via the netmap interface are no longer counted in the stats
for the "main" interface, but are not accounted to the netmap interface.

The netmap interfaces now also have a new-bus device and export various
information sysctl nodes via dev.n(cxgbe|cxl).X.

The cxgbetool 'clearstats' command clears the stats for all VIs on the
specified port along with the port's stats.  There is currently no way to
clear the stats of an individual VI.

Reviewed by:	np
MFC after:	1 month
Sponsored by:	Chelsio
2015-12-03 00:02:01 +00:00
Navdeep Parhar
8faf57012b cxgbe(4): Save the flags for the last adapter-wide synchronized
operation that was initiated successfully.  (The caller and thread are
already recorded).

MFC after:	1 week
2015-08-19 15:40:03 +00:00
Navdeep Parhar
a1ed88571f cxgbe(4): Ask the firmware for the start of the RSS slice for a port and
save it for later.  This enables direct manipulation of the indirection
tables (although the stock driver doesn't do that right now).

MFC after:	1 month
2015-07-17 06:46:18 +00:00
Navdeep Parhar
9af71ab3bc cxgbe(4): Add a new knob that controls the congestion response of netmap
rx queues.  The default is to drop rather than backpressure.

This decouples the congestion settings of NIC and netmap rx queues.

MFC after:	3 days
2015-07-06 20:56:59 +00:00
Navdeep Parhar
0e4cd4a2e0 cxgbe(4): Add the ability to dump mailbox commands and replies. It is
enabled/disabled via bit 0 of adapter->debug_flags (which is available
at dev.t5nex.<n>.debug_flags).

MFC after:	1 week
2015-06-16 12:36:29 +00:00
Navdeep Parhar
1605bac6fb cxgbe(4): set up congestion management for netmap rx queues.
The hw.cxgbe.cong_drop knob controls the response of the chip when
netmap queues are congested.
2015-02-24 18:40:10 +00:00
Navdeep Parhar
b3d44a6800 cxgbe(4): tidy up some of the interaction between the Upper Layer
Drivers (ULDs) and the base if_cxgbe driver.

Track the per-adapter activation of ULDs in a new "active_ulds" field.
This was done pretty arbitrarily before this change -- via TOM_INIT_DONE
in adapter->flags for TOM, and the (1 << MAX_NPORTS) bit in
adapter->offload_map for iWARP.

iWARP and hw-accelerated iSCSI rely on the TOE (supported by the TOM
ULD).  The rules are:
a) If the iWARP and/or iSCSI ULDs are available when TOE is enabled then
   iWARP and/or iSCSI are enabled too.
b) When the iWARP and iSCSI modules are loaded they go looking for
   adapters with TOE enabled and enable themselves on that adapter.
c) You cannot deactivate or unload the TOM module from underneath iWARP
   or iSCSI.  Any such attempt will fail with EBUSY.

MFC after:	2 weeks
2015-02-08 09:28:55 +00:00
Navdeep Parhar
d86a5ff917 cxgbe(4): a change to the synchronization rules within the the driver.
This is purely cosmetic because the new rules are already followed.

MFC after:	1 week
2015-02-08 08:42:45 +00:00
Navdeep Parhar
7951040f8a cxgbe(4): major tx rework.
a) Front load as much work as possible in if_transmit, before any driver
lock or software queue has to get involved.

b) Replace buf_ring with a brand new mp_ring (multiproducer ring).  This
is specifically for the tx multiqueue model where one of the if_transmit
producer threads becomes the consumer and other producers carry on as
usual.  mp_ring is implemented as standalone code and it should be
possible to use it in any driver with tx multiqueue.  It also has:
- the ability to enqueue/dequeue multiple items.  This might become
  significant if packet batching is ever implemented.
- an abdication mechanism to allow a thread to give up writing tx
  descriptors and have another if_transmit thread take over.  A thread
  that's writing tx descriptors can end up doing so for an unbounded
  time period if a) there are other if_transmit threads continuously
  feeding the sofware queue, and b) the chip keeps up with whatever the
  thread is throwing at it.
- accurate statistics about interesting events even when the stats come
  at the expense of additional branches/conditional code.

The NIC txq lock is uncontested on the fast path at this point.  I've
left it there for synchronization with the control events (interface
up/down, modload/unload).

c) Add support for "type 1" coalescing work request in the normal NIC tx
path.  This work request is optimized for frames with a single item in
the DMA gather list.  These are very common when forwarding packets.
Note that netmap tx in cxgbe already uses these "type 1" work requests.

d) Do not request automatic cidx updates every 32 descriptors.  Instead,
request updates via bits in individual work requests (still every 32
descriptors approximately).  Also, request an automatic final update
when the queue idles after activity.  This means NIC tx reclaim is still
performed lazily but it will catch up quickly as soon as the queue
idles.  This seems to be the best middle ground and I'll probably do
something similar for netmap tx as well.

e) Implement a faster tx path for WRQs (used by TOE tx and control
queues, _not_ by the normal NIC tx).  Allow work requests to be written
directly to the hardware descriptor ring if room is available.  I will
convert t4_tom and iw_cxgbe modules to this faster style gradually.

MFC after:	2 months
2014-12-31 23:19:16 +00:00
Navdeep Parhar
a7570ee305 Move KTR_CXGBE from t4_tom.h to adapter.h so that the base if_cxgbe
code can use it too.

MFC after:	1 week
2014-12-12 21:54:59 +00:00
Navdeep Parhar
b741402c40 cxgbe(4): allow the driver to use rx buffers that do not end on a pack
boundary.

MFC after:	2 weeks
2014-12-06 01:47:38 +00:00
Navdeep Parhar
e3207e1973 cxgbe(4): Allow for different pad and pack boundaries for different
adapters.  Set the pack boundary for T5 cards to be the same as the
PCIe max payload size.  The chip likes it this way.

In this revision the driver allocate rx buffers that align on both
boundaries.  This is not a strict requirement and a followup commit
will switch the driver to a more relaxed allocation strategy.

MFC after:	2 weeks
2014-12-06 00:13:56 +00:00
Navdeep Parhar
2d8910854b cxgbe(4): implement if_get_counter. 2014-09-27 05:50:31 +00:00
Navdeep Parhar
4d6db4e0f7 cxgbe(4): some optimizations in freelist handling.
MFC after:	2 weeks.
2014-08-02 06:55:36 +00:00
Navdeep Parhar
b2daa9a9cd cxgbe(4): minor optimizations in ingress queue processing.
Reorganize struct sge_iq.  Make the iq entry size a compile time
constant.  While here, eliminate RX_FL_ESIZE and use EQ_ESIZE directly.

MFC after:	2 weeks
2014-08-02 00:56:34 +00:00
Navdeep Parhar
82eff304b6 cxgbe(4): Keep track of the clusters that have to be freed by the
custom free routine (rxb_free) in the driver.  Fail MOD_UNLOAD with
EBUSY if any such cluster has been handed up to the kernel but hasn't
been freed yet.  This prevents a panic later when the cluster finally
needs to be freed but rxb_free is gone from the kernel.

MFC after:	1 week
2014-07-23 22:29:22 +00:00
Navdeep Parhar
c3fb772502 Simplify r267600, there's no need to distinguish between allocated and
inlined mbufs.

MFC after:	1 week
2014-07-22 02:02:39 +00:00
Navdeep Parhar
30f337891d cxgbe(4): Add an iSCSI softc to the adapter structure. 2014-07-11 21:02:54 +00:00
Navdeep Parhar
ccc69b2fa9 cxgbe(4): Fix bug in the fast rx buffer recycle path. In some cases rx
buffers were getting recycled when they should have been left alone.

MFC after:	3 days
2014-06-18 00:16:35 +00:00
Navdeep Parhar
298d969c53 cxgbe(4): netmap support for Terminator 5 (T5) based 10G/40G cards.
Netmap gets its own hardware-assisted virtual interface and won't take
over or disrupt the "normal" interface in any way.  You can use both
simultaneously.

For kernels with DEV_NETMAP, cxgbe(4) carves out an ncxl<N> interface
(note the 'n' prefix) in the hardware to accompany each cxl<N>
interface.  These two ifnet's per port share the same wire but really
are separate interfaces in the hardware and software.  Each gets its own
L2 MAC addresses (unicast and multicast), MTU, checksum caps, etc.  You
should run netmap on the 'n' interfaces only, that's what they are for.

With this, pkt-gen is able to transmit > 45Mpps out of a single 40G port
of a T580 card.  2 port tx is at ~56Mpps total (28M + 28M) as of now.
Single port receive is at 33Mpps but this is very much a work in
progress.  I expect it to be closer to 40Mpps once done.  In any case
the current effort can already saturate multiple 10G ports of a T5 card
at the smallest legal packet size.  T4 gear is totally untested.

trantor:~# ./pkt-gen -i ncxl0 -f tx -D 00:07:43🆎cd:ef
881.952141 main [1621] interface is ncxl0
881.952250 extract_ip_range [275] range is 10.0.0.1:0 to 10.0.0.1:0
881.952253 extract_ip_range [275] range is 10.1.0.1:0 to 10.1.0.1:0
881.962540 main [1804] mapped 334980KB at 0x801dff000
Sending on netmap:ncxl0: 4 queues, 1 threads and 1 cpus.
10.0.0.1 -> 10.1.0.1 (00:00:00:00:00:00 -> 00:07:43🆎cd:ef)
881.962562 main [1882] Sending 512 packets every  0.000000000 s
881.962563 main [1884] Wait 2 secs for phy reset
884.088516 main [1886] Ready...
884.088535 nm_open [457] overriding ifname ncxl0 ringid 0x0 flags 0x1
884.088607 sender_body [996] start
884.093246 sender_body [1064] drop copy
885.090435 main_thread [1418] 45206353 pps (45289533 pkts in 1001840 usec)
886.091600 main_thread [1418] 45322792 pps (45375593 pkts in 1001165 usec)
887.092435 main_thread [1418] 45313992 pps (45351784 pkts in 1000834 usec)
888.094434 main_thread [1418] 45315765 pps (45406397 pkts in 1002000 usec)
889.095434 main_thread [1418] 45333218 pps (45378551 pkts in 1001000 usec)
890.097434 main_thread [1418] 45315247 pps (45405877 pkts in 1002000 usec)
891.099434 main_thread [1418] 45326515 pps (45417168 pkts in 1002000 usec)
892.101434 main_thread [1418] 45333039 pps (45423705 pkts in 1002000 usec)
893.103434 main_thread [1418] 45324105 pps (45414708 pkts in 1001999 usec)
894.105434 main_thread [1418] 45318042 pps (45408723 pkts in 1002001 usec)
895.106434 main_thread [1418] 45332430 pps (45377762 pkts in 1001000 usec)
896.107434 main_thread [1418] 45338072 pps (45383410 pkts in 1001000 usec)
...

Relnotes:	Yes
Sponsored by:	Chelsio Communications.
2014-05-27 18:18:41 +00:00
Navdeep Parhar
38035ed6dc cxgbe(4): significant rx rework.
- More flexible cluster size selection, including the ability to fall
  back to a safe cluster size (PAGE_SIZE from zone_jumbop by default) in
  case an allocation of a larger size fails.
- A single get_fl_payload() function that assembles the payload into an
  mbuf chain for any kind of freelist.  This replaces two variants: one
  for freelists with buffer packing enabled and another for those without.
- Buffer packing with any sized cluster.  It was limited to 4K clusters
  only before this change.
- Enable buffer packing for TOE rx queues as well.
- Statistics and tunables to go with all these changes.  The driver's
  man page will be updated separately.

MFC after:	5 weeks
2014-03-18 20:14:13 +00:00
Scott Long
f7a74e061b Add a new sysctl, dev.cxgbe.N.rsrv_noflow, and a companion tunable,
hw.cxgbe.rsrv_noflow.  When set, queue 0 of the port is reserved for
TX packets without a flowid.  The hash value of packets with a flowid
is bumped up by 1.  The intent is to provide a private queue for
link-level packets like LACP that is unlikely to overflow or suffer
deep queue latency.

Reviewed by:	np
Obtained from:	Netflix
MFC after:	3 days
2014-02-06 18:40:38 +00:00
Navdeep Parhar
e46dcc5670 cxgbe(4): Use the rx channel map (instead of the tx channel map) as the
congestion channel map.

MFC after:	1 week
2014-02-06 03:30:12 +00:00
Navdeep Parhar
7293a15f54 cxgbe(4): The T5 allows for a different freelist starvation threshold
for queues with buffer packing.  Use the correct value to calculate a
freelist's low water mark.

MFC after:	1 week
2014-02-06 03:21:43 +00:00
Adrian Chadd
3af0f449ae Add an option to enable or disable the small RX packet copying that
is done to improve performance of small frames.

When doing RX packing, the RX copying isn't necessarily required.

Reviewed by:	np
2014-01-02 23:23:33 +00:00
Navdeep Parhar
273ef9912d cxgbe(4): save a copy of the RSS map for each port for the driver's use. 2013-12-08 17:47:37 +00:00
Gleb Smirnoff
76039bc84f The r48589 promised to remove implicit inclusion of if_var.h soon. Prepare
to this event, adding if_var.h to files that do need it. Also, include
all includes that now are included due to implicit pollution via if_var.h

Sponsored by:	Netflix
Sponsored by:	Nginx, Inc.
2013-10-26 17:58:36 +00:00
Navdeep Parhar
b3eda7872d cxgbe(4): Store the log2 of the # of doorbells per BAR2 page for both
ingress and egress queues, and for both T4 and T5.  These values are
used by the T4/T5 iWARP driver.
2013-10-14 23:32:56 +00:00
Navdeep Parhar
1458bff9a4 Implement support for rx buffer packing. Enable it by default for T5
cards.

This is a T4 and T5 chip feature which lets the chip deliver multiple
Ethernet frames in a single buffer.  This is more efficient within the
chip, in the driver, and reduces wastage of space in rx buffers.

- Always allocate rx buffers from the jumbop zone, no matter what the
  MTU is.  Do not use the normal cluster refcounting mechanism.
- Reserve space for an mbuf and a refcount in the cluster itself and let
  the chip DMA multiple frames in the rest.
- Use the embedded mbuf for the first frame and allocate mbufs on the
  fly for any additional frames delivered in the cluster.  Each of these
  mbufs has a reference on the underlying cluster.
2013-08-30 01:45:36 +00:00