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Date: Tue, 11 Nov 2003 02:39:49 -0800
From: Terry Lambert <tlambert2@mindspring.com>
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To: Alex Wilkinson <alex.wilkinson@dsto.defence.gov.au>
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Subject: Re: erroneous message from locked-up machine
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Alex Wilkinson wrote:
> Can someone please elaborate on the acronym KVA ?
> 
> $ sysctl -d kern.ipc.maxpipekva
> kern.ipc.maxpipekva: Pipe KVA limit
> 
> This doesn't tell me enough.

Kernel Virtual Address

The fast pipe code in FreeBSD uses page lending between the
processes participating in the pipe endpoints, so it uses a
set of wired memory to do its job.  By definition, this means
that it takes a chunk of KVA space in order to get the wired
memory.

This tunable value is an administrative limit on the amount
of KVA that can be used up by pipes.  In general, you should
never feel this, unless you are doing strange things with your
pipes.  Massively parallel compiles using pipes to communicate
between the compiler stages, for example.

-- Terry