Re: Perform mmap and poll on PUD character devices

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Sat, Sep 10, 2011 at 12:05:53PM +0200, Roger Pau Monné wrote:
> Hello,
> 
> Thanks for the reply, sometimes I'm so focused in the problem that I
> forget the big picture. PUD is a framework present in NetBSD that
> allows to implement character and block devices in userspace. [1]
> 
> The blktap (?block tap?) userspace toolkit provides a user-level disk
> I/O interface in Xen systems. Its current main application is to
> replace the common loopback driver for file-based images because of
> better performance. The blktap mechanism involves a kernel driver

I can't see how a userland implementation can have better performances
than an all in-kernel implementation. There are more context switches,
which are notr so cheap with Xen.

But a blktap implementation may be usefull for other reasons ...

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--