>> I have an application that makes outbound TCP connections at a very
>> high rate, so high that the overhead of additional system calls to
>> set socket options considerably impacts performance.
> That sounds as though there is something badly wrong in the code
> paths somewhere.

Maybe, but I'm not so sure.

> Even allowing for the system calls costs, I'm surprised that
> setsockopt() gets anywhere near the cost of connect().

Some processors make crossing the kernel/user boundary very expensive.
That crossing can be a substantial portion of the cost of a call such
as setsockopt() - or even connect(), especially async connect() (which
is probably what's going on).

Upon considering that Thor's code was probably doing at least a
half-dozen setsockopt() calls for each socket, I find it totally
plausible that doing (say) eight syscalls instead of two for each
connection could "considerably" impact performance.

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