Re: Merging relayfs?

[Roman Zippel <zippel@linux-m68k.org>]

Hi,

On Mon, 11 Jul 2005, Andrew Morton wrote:

> > > Hi Andrew, can you please merge relayfs?  It provides a low-overhead
> > > logging and buffering capability, which does not currently exist in
> > > the kernel.
> > 
> > While the code is pretty nicely in shape it seems rather pointless to
> > merge until an actual user goes with it.
> 
> Ordinarily I'd agree.  But this is a bit like kprobes - it's a funny thing
> which other kernel features rely upon, but those features are often ad-hoc
> and aren't intended for merging.

I agree with Christoph, I'd like to see a small (and useful) example 
included, which can be used as reference. relayfs client still need some 
code of their own to communicate with user space. If I look at the example 
code I'm not really sure netlink is a good way to go as control channel.
kprobes has a rather simple interface, relayfs is more complex and I think 
it's a good idea to provide some sane and complete example code to copy 
from.

Looking through the patch there are still a few areas I'm concerned about:
- the usage of atomic_t look a little silly, there is only a single 
writer and probably needs some cache line optimisations
- I would prefer "unsigned int" over just "unsigned"
- the padding/commit arrays can be easily managed by the client
- overwrite mode can be implemented via the buffer switch callback

In general I'm not against merging, but I have a few ideas for further 
cleanups/optimisations and it really would help to have some useful 
example code (e.g. a _simple_ event tracer).

bye, Roman
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