Subject: Re: Proposal: socketfrom()
To: None <tech-net@NetBSD.org>
From: der Mouse <mouse@Rodents.Montreal.QC.CA>
Date: 07/05/2007 03:02:15
>> 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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