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由 Ido Schimmel 提交于
When packets ingress the switch they are assigned a switch priority and directed to the corresponding priority group (PG) buffer in the port's headroom buffer. Since we now map all switch priorities to priority group 0 (PG0) by default, there is no need to allocate the other priority groups during initialization. The only exception is PG9, which is used for control traffic. At minimum, the PG should be able to store the currently classified packet (pipeline latency isn't 0) and also the packets arriving during the classification time. However, an incoming packet will not be buffered if there is no available MTU-sized buffer space for storing it. The buffer needed to accommodate for pipeline latency is variable and needs to take into account both the current link speed and current latency of the pipeline, which is time-dependent. Testing showed that setting the PG's size to twice the current MTU is optimal. Since PG9 is used strictly for control packets and not subject to flow control, we are not going to resize it according to user configuration, so we simply set it according to worst case scenario, which is twice the maximum MTU. In any case, later patches in the series will allow a user to direct lossless flows to other PGs than PG0 and set their size to accommodate for round-trip propagation delay. The above change also requires us to resize the PG buffer whenever the port's MTU is changed. Signed-off-by: NIdo Schimmel <idosch@mellanox.com> Signed-off-by: NJiri Pirko <jiri@mellanox.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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