r200088:
Add workaround to overcome hardware limitation which allows only a
single outstanding DMA read operation. Most controllers targeted to
client with PCIe bus interface(e.g. BCM5761) may have this
limitation. All controllers for servers does not have this
limitation.
Collapsing mbuf chains to reduce number of memory reads before
transmitting was most effective way to workaround this. I got about
940Mbps from 850Mbps with mbuf collapsing on BCM5761. However it
takes a lot of CPU cycles to collapse mbuf chains so add tunable to
control the number of allowed TX buffers before collapsing. The
default value is 0 which effectively disables the forced collapsing.
For most cases 2 would yield best performance(about 930Mbps)
without much sacrificing CPU cycles.
Note the collapsing is only activated when the controller is on
PCIe bus and the frame does not need TSO operation. TSO does not
seem to suffer from the hardware limitation because the payload
size is much bigger than normal IP datagram.
Thanks to davidch@ who told me the limitation of client controllers
and actually gave possible workarounds to mitigate the limitation.
r200227:
Remove PHY isolate/power down code in bge_stop(). The isolation
handler in brgphy(4) does not exist and brgphy(4) just resets the
PHY and returns EINVAL as it has no isolation handler. I also agree
on Marius's opinion that stop handler of every NIC driver seems to
be the wrong place for implementing PHY isolate/power down.
If we need PHY isolate/power down it should be implemented in
brgphy(4) and users should administratively down the PHY.
r200228:
Don't access jumbo frame related registers if controller lacks the
feature. These registers are reserved on controllers that have no
support for jumbo frame.
Only BCM5700 has mini ring so do not poke mini ring related
registers if controller is not BCM5700.
r200246:
Partially revert r200228. For mini RCB case, bge(4) still have to
disable mini ring withtout regard to mini ring support.
r200264:
Create sysctl node(dev.bge.%d.focred_collapse) instead of
hw.bge.forced_collapse. hw.bge.forced_collapse affects all bge(4)
controllers on system which may not desirable behavior of the
sysctl node. Also allow the sysctl node could be modified at any
time.
r201446:
Fix regression introduced in r198318. BCM5754/BCM5754M uses the
same ASIC ID of BCM5758 such that r198318 incorecctly enabled TSO
on BCM5754.BCM5754M controllers. BCM5754/BCM5754M needs a special
firmware to enable TSO and bge(4) does not support firmware based
TSO.
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