Re: netlink vs. debugfs (was Re: [Patch 0/6] statistics infrastructure)

Re: netlink vs. debugfs (was Re: [Patch 0/6] statistics infrastructure)

[Balbir Singh]

On Mon, May 22, 2006 at 11:09:22AM -0700, Tim Bird wrote:
> Andrew Morton wrote:
> > Martin Peschke <mp3@de.ibm.com> wrote:
> >> My patch series is a proposal for a generic implementation of statistics.
> > 
> > This uses debugfs for the user interface, but the
> > per-task-delay-accounting-*.patch series from Balbir creates an extensible
> > netlink-based system for passing instrumentation results back to userspace.
> > 
> > Can this code be converted to use those netlink interfaces, or is Balbir's
> > approach unsuitable, or hasn't it even been considered, or what?
> 
> Can someone give me the 20-second elevator pitch on why
> netlink is preferred over debugfs?  I've heard of a
> number of debugfs/procfs users requested to switch over.
> 
> Thanks,
>  -- Tim
> 
> =============================
> Tim Bird
> Architecture Group Chair, CE Linux Forum
> Senior Staff Engineer, Sony Electronics
> =============================

Hi, Tim,

I am no debugfs expert, I hope I can do justice to the comparison.

Debugfs						Netlink/Genetlink

1. Filesystem based - requires creating		Several types of data can
   files for each type of data passed		be multiplexed over one netlink
   down						socket.
2. Hard to determine record format/data		Contains metadata including
						type of data and length
						with each record
3. Notifications are hard			Notifications are very easy
   I think they can be done using inotify	good library support for
						notifications. Data can
						either be broadcast or
						selectively mulitcast
4. Requires several open/read/write/close	A single socket can be
   operations					opened, data from kernel
						space can be multiplexed
						over it.

I don't think I did any justice to the advantages of debugfs. The only
one I can think of is that it uses relayfs. Relayfs is efficient in the
sense that it uses per-cpu buffers.

Anybody else want to take a shot in comparing the two?

	Balbir Singh,
	Linux Technology Center,
	IBM Software Labs

Re: netlink vs. debugfs (was Re: [Patch 0/6] statistics infrastructure)

[Evgeniy Polyakov]

On Tue, May 23, 2006 at 12:04:00AM +0530, Balbir Singh (balbir@in.ibm.com) wrote:
> Anybody else want to take a shot in comparing the two?

Netlink is always presented in the kernel, so no need to make
additional dependencies for special FS.
But number of netlink sockets is not that big, so use new one if you
create really generic mechanism, or consider using connector/gennetlink.

-- 
	Evgeniy Polyakov