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From: Fred Pedrisa <fredhps10@hotmail.com>
To: "'Jan Bramkamp'" <crest@rlwinm.de>,
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Subject: RES: KQueue vs Select (NetMap)
Date: Thu, 29 May 2014 00:53:41 -0300
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Hello,

Yes, but kqueue support was added in recent commits as it says in the netmap
changelog, is there any advantage ?

-----Mensagem original-----
De: owner-freebsd-current@freebsd.org
[mailto:owner-freebsd-current@freebsd.org] Em nome de Jan Bramkamp
Enviada em: quinta-feira, 29 de maio de 2014 00:30
Para: freebsd-current@freebsd.org
Assunto: Re: KQueue vs Select (NetMap)


On 29.05.2014 03:04, Fred Pedrisa wrote:
> Hey Guys,
>
>  
>
> How does kQueue performs over select with netmap ?
You are asking for a comparison between apples and oranges. Netmap is an API
for high performance access to the low-level features of modern NICs. It
works on batches of frames in hardware queues.

The kqueue() and kevent() system calls are an event notification API. It is
mostly used by application dealing with a large amount of non-blocking
sockets (or other file descriptors). It reduces overhead inherent in
select() and poll() by preserving state between calls. It also supports
multiple types of events (read ready, write ready, timer expired, async i/o,
etc.).

Afaik the netmap pseudo-device supports only select() and poll(). This is no
performance problem because every thread will only deal with a small number
of file descriptors to netmap devices.

Netmap is designed to bypass the FreeBSD IP stack (for most frames).
Kqueue is designed to scale to many sockets per process within the FreeBSD
IP stack.
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