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inet6_ehashfn() being called from __inet6_check_established() has a big impact on performance, as shown in the Tested section. After prior patch, we can compute the hash for port 0 from inet6_hash_connect(), and derive each hash in __inet_hash_connect() from this initial hash: hash(saddr, lport, daddr, dport) == hash(saddr, 0, daddr, dport) + lport Apply the same principle for __inet_check_established(), although inet_ehashfn() has a smaller cost. Tested: Server: ulimit -n 40000; neper/tcp_crr -T 200 -F 30000 -6 --nolog Client: ulimit -n 40000; neper/tcp_crr -T 200 -F 30000 -6 --nolog -c -H server Before this patch: utime_start=0.286131 utime_end=4.378886 stime_start=11.952556 stime_end=1991.655533 num_transactions=1446830 latency_min=0.001061085 latency_max=12.075275028 latency_mean=0.376375302 latency_stddev=1.361969596 num_samples=306383 throughput=151866.56 perf top: 50.01% [kernel] [k] __inet6_check_established 20.65% [kernel] [k] __inet_hash_connect 15.81% [kernel] [k] inet6_ehashfn 2.92% [kernel] [k] rcu_all_qs 2.34% [kernel] [k] __cond_resched 0.50% [kernel] [k] _raw_spin_lock 0.34% [kernel] [k] sched_balance_trigger 0.24% [kernel] [k] queued_spin_lock_slowpath After this patch: utime_start=0.315047 utime_end=9.257617 stime_start=7.041489 stime_end=1923.688387 num_transactions=3057968 latency_min=0.003041375 latency_max=7.056589232 latency_mean=0.141075048 # Better latency metrics latency_stddev=0.526900516 num_samples=312996 throughput=320677.21 # 111 % increase, and 229 % for the series perf top: inet6_ehashfn is no longer seen. 39.67% [kernel] [k] __inet_hash_connect 37.06% [kernel] [k] __inet6_check_established 4.79% [kernel] [k] rcu_all_qs 3.82% [kernel] [k] __cond_resched 1.76% [kernel] [k] sched_balance_domains 0.82% [kernel] [k] _raw_spin_lock 0.81% [kernel] [k] sched_balance_rq 0.81% [kernel] [k] sched_balance_trigger 0.76% [kernel] [k] queued_spin_lock_slowpath Signed-off-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com> Tested-by: Jason Xing <kerneljasonxing@gmail.com> Reviewed-by: Jason Xing <kerneljasonxing@gmail.com> Link: https://patch.msgid.link/20250305034550.879255-3-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.