Merge branch 'tcp-even-faster-connect-under-stress'

Eric Dumazet says:

====================
tcp: even faster connect() under stress

This is a followup on the prior series, "tcp: scale connect() under pressure"

Now spinlocks are no longer in the picture, we see a very high cost
of the inet6_ehashfn() function.

In this series (of 2), I change how lport contributes to inet6_ehashfn()
to ensure better cache locality and call inet6_ehashfn()
only once per connect() system call.

This brings an additional 229 % increase of performance
for "neper/tcp_crr -6 -T 200 -F 30000" stress test,
while greatly improving latency metrics.

Before:
  latency_min=0.014131929
  latency_max=17.895073144
  latency_mean=0.505675853
  latency_stddev=2.125164772
  num_samples=307884
  throughput=139866.80

After:
  latency_min=0.003041375
  latency_max=7.056589232
  latency_mean=0.141075048
  latency_stddev=0.526900516
  num_samples=312996
  throughput=320677.21
====================

Link: https://patch.msgid.link/20250305034550.879255-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>