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Eric Dumazet says: ==================== tcp: scale connect() under pressure Adoption of bhash2 in linux-6.1 made some operations almost twice more expensive, because of additional locks. This series adds RCU in __inet_hash_connect() to help the case where many attempts need to be made before finding an available 4-tuple. This brings a ~200 % improvement in this experiment: 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 series: utime_start=0.288582 utime_end=1.548707 stime_start=20.637138 stime_end=2002.489845 num_transactions=484453 latency_min=0.156279245 latency_max=20.922042756 latency_mean=1.546521274 latency_stddev=3.936005194 num_samples=312537 throughput=47426.00 perf top on the client: 49.54% [kernel] [k] _raw_spin_lock 25.87% [kernel] [k] _raw_spin_lock_bh 5.97% [kernel] [k] queued_spin_lock_slowpath 5.67% [kernel] [k] __inet_hash_connect 3.53% [kernel] [k] __inet6_check_established 3.48% [kernel] [k] inet6_ehashfn 0.64% [kernel] [k] rcu_all_qs After this series: utime_start=0.271607 utime_end=3.847111 stime_start=18.407684 stime_end=1997.485557 num_transactions=1350742 latency_min=0.014131929 latency_max=17.895073144 latency_mean=0.505675853 # Nice reduction of latency metrics latency_stddev=2.125164772 num_samples=307884 throughput=139866.80 # 194 % increase perf top on client: 56.86% [kernel] [k] __inet6_check_established 17.96% [kernel] [k] __inet_hash_connect 13.88% [kernel] [k] inet6_ehashfn 2.52% [kernel] [k] rcu_all_qs 2.01% [kernel] [k] __cond_resched 0.41% [kernel] [k] _raw_spin_lock ==================== Link: https://patch.msgid.link/20250302124237.3913746-1-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.