Q: why can’t we extend m_get2 to not fail for 9..16k packets?

Please do not introduce new usages of mbuf clusters > PAGE_SIZE into
the network stack. When under memory pressure attempting to
allocating >PAGE_SIZE clusters will DoS the whole system if done at
the packet rates seen on modern networks.

In D31455#709082, @rstone wrote:

Please do not introduce new usages of mbuf clusters > PAGE_SIZE into
the network stack. When under memory pressure attempting to
allocating >PAGE_SIZE clusters will DoS the whole system if done at
the packet rates seen on modern networks.

This particular use case (in f13da24715a7) is for bpf, so not directly in the data path, and it shouldn't be allocating millions of times per second. I suppose that does form a good argument for not extending m_get2() rather than having an m_get3() (or keeping the current bpf approach of m_get2()/m_getjcl()).