Rajagopal Kunhappan wrote:
The tuning that you have done is rather weird. By default,
ip_squeues_per_cpu has a value of 1. But that does not mean that only
one squeue will be there for a CPU. More squeues upto a maximum of 32
can get allocated for a CPU and they get allocated on demand. So setting
ip_squeues_per_cpu to 32 is not very interesting.
What is interesting is that you have set ip_soft_rings_cnt to 2 times
ip_squeues_per_cpu which would be 64 in your case. This does not seem
right.
If you have a 64 CPU system and want to use all of them to process
incoming packets for a NIC, then it may just be ok, but having more soft
rings than the number of CPUs does not give you any performance advantage.
My suggestion is to not change ip_squeues_per_cpu at all but tune
ip_soft_rings_cnt only. Set it to 2 or 3 for 1Gbps NIC and anywhere from
16 to 32 for 10 Gbps NIC. Again don't increase the soft ring count to
more than the number of CPUs in the system. Also note that CPU speed is
also important in the calculation. A simple rule of thumb is that a 1Ghz
CPU should be able to handle a 1Gbps NIC.
Could all of this manual tuning be made obsolete by some simple
heuristics in the code which could automatically set these things? The
number of CPUs on the system is no secret to the kernel. Will any of
the ongoing projects (such as Crossbow or PEF) make this situation better?
-Seb
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