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Old 02-15-2010, 06:20 PM
Enrico Weigelt
 
Default How the HAL are you supposed to use these files?

J. Roeleveld wrote:

>> And *IF* some application is interested in the such information,
>> why not just using the filesystem ?
>
> Because on flash-drives (Which are used in small devices and netbooks) you
> don't want every single status update to be written to the filesystem.
> And with minimal memory, I don't want to have a ram-disk gobbling up the
> memory I have.

Why not simply using tmpfs ?
Or an specific synthetic filesystem ? 9P makes this really easy,
and network agnostic.


cu
--
----------------------------------------------------------------------
Enrico Weigelt, metux IT service -- http://www.metux.de/

cellphone: +49 174 7066481 email: info@metux.de skype: nekrad666
----------------------------------------------------------------------
Embedded-Linux / Portierung / Opensource-QM / Verteilte Systeme
----------------------------------------------------------------------
 
Old 02-15-2010, 07:23 PM
Mike Edenfield
 
Default How the HAL are you supposed to use these files?

On 2/15/2010 2:20 PM, Enrico Weigelt wrote:

J. Roeleveld wrote:


And *IF* some application is interested in the such information,
why not just using the filesystem ?


Because on flash-drives (Which are used in small devices and netbooks) you
don't want every single status update to be written to the filesystem.
And with minimal memory, I don't want to have a ram-disk gobbling up the
memory I have.


Why not simply using tmpfs ?
Or an specific synthetic filesystem ? 9P makes this really easy,
and network agnostic.


I'm kinda stunned that your arguments against D-Bus seems to boil down
to "just use 9p instead" given that plumber is a basic element of 9p and
does essentially the same job D-Bus does. So you're just swapping one
system-wide general-purpose IPC service out for another one?
 
Old 02-15-2010, 10:41 PM
Volker Armin Hemmann
 
Default How the HAL are you supposed to use these files?

On Montag 15 Februar 2010, Mike Edenfield wrote:
> On 2/15/2010 2:20 PM, Enrico Weigelt wrote:
> > J. Roeleveld wrote:
> >>> And *IF* some application is interested in the such information,
> >>> why not just using the filesystem ?
> >>
> >> Because on flash-drives (Which are used in small devices and netbooks)
> >> you don't want every single status update to be written to the
> >> filesystem. And with minimal memory, I don't want to have a ram-disk
> >> gobbling up the memory I have.
> >
> > Why not simply using tmpfs ?
> > Or an specific synthetic filesystem ? 9P makes this really easy,
> > and network agnostic.
>
> I'm kinda stunned that your arguments against D-Bus seems to boil down
> to "just use 9p instead" given that plumber is a basic element of 9p and
> does essentially the same job D-Bus does. So you're just swapping one
> system-wide general-purpose IPC service out for another one?

he is just trolling around.
 
Old 02-16-2010, 07:23 AM
"J. Roeleveld"
 
Default How the HAL are you supposed to use these files?

On Monday 15 February 2010 20:20:53 Enrico Weigelt wrote:
> J. Roeleveld wrote:
> >> And *IF* some application is interested in the such information,
> >> why not just using the filesystem ?
> >
> > Because on flash-drives (Which are used in small devices and netbooks)
> > you don't want every single status update to be written to the
> > filesystem. And with minimal memory, I don't want to have a ram-disk
> > gobbling up the memory I have.
>
> Why not simply using tmpfs ?
> Or an specific synthetic filesystem ? 9P makes this really easy,
> and network agnostic.

Netbook: 1GB of ram, with Linux, I can easily run all the software I want ,
without need of any swap.
Can I do the same with 9P? Eg. will I be able to run all the software I use on
my netbook without having to spent time on porting it all?
Is also all the hardware supported in 9P? Linux supports all the hardware in
my netbook.

Unless the answer to this is a 100% yes, 9P is never going to be an option.

--
Joost
 
Old 02-16-2010, 01:32 PM
Mike Edenfield
 
Default How the HAL are you supposed to use these files?

On 2/16/2010 3:23 AM, J. Roeleveld wrote:


Netbook: 1GB of ram, with Linux, I can easily run all the software I want ,
without need of any swap.
Can I do the same with 9P? Eg. will I be able to run all the software I use on
my netbook without having to spent time on porting it all?
Is also all the hardware supported in 9P? Linux supports all the hardware in
my netbook.

Unless the answer to this is a 100% yes, 9P is never going to be an option.


Just for reference, 9p is not Plan 9, it's only the Plan 9 network
protocol/distributed file system, which you can use on Linux with the
appropriate file system modules.


--Mike
 
Old 02-16-2010, 05:05 PM
Enrico Weigelt
 
Default How the HAL are you supposed to use these files?

Mike Edenfield wrote:

> Just for reference, 9p is not Plan 9, it's only the Plan 9 network
> protocol/distributed file system, which you can use on Linux with the
> appropriate file system modules.

Right. Either you use the kernel module (which now is in mainline
for quite a long time), or 9pfuse, or one of the userland libraries
around (eg. libmvfs).

The basic idea behind this all is to use a filesystem as a primary
IPC interface. Files dont necessarily mean things stored on-disk,
but streams/communication-channels in an hierachical namespace.
(eg. /proc or /sys).

This way you have a very simple IPC mechanism using the very same
semantics as filesystems do traditionally. That's just consequently
using the "everything's a file"-metaphor. As everything's a file,
all an OS or an distributed environment has to provide is dispatching
filesystem operations from client to server, whereever they may
actually reside. For example, you can simply mount any Plan9 device
via 9P, from anywhere, as long as you get some 9P path there.


(BTW: 9P doesnt have the concept of ioctl()s. If some object has
more than just a single IO stream, it's modeled as an directory,
eg. containing some "ctl" file accepting additional commands, etc).


cu
--
----------------------------------------------------------------------
Enrico Weigelt, metux IT service -- http://www.metux.de/

cellphone: +49 174 7066481 email: info@metux.de skype: nekrad666
----------------------------------------------------------------------
Embedded-Linux / Portierung / Opensource-QM / Verteilte Systeme
----------------------------------------------------------------------
 
Old 02-16-2010, 06:00 PM
Enrico Weigelt
 
Default How the HAL are you supposed to use these files?

Mike Edenfield wrote:

> I'm kinda stunned that your arguments against D-Bus seems to boil down
> to "just use 9p instead"

No, we're talking about very different concepts. D-Bus is essentially
an generic RPC mechanism (with an asychronous signalling facility).
So it allows calling procedures on remote objects sending signals
to listeners. IOW: fundamental concept behind GObject, QObject, etc
put onto distributed level (but much simpler than CORBA, etc).

On the other hand, 9P is essentially just a filesystem protocol
which is very well suited for synthetic filesystems. The latter
is the key point: synthetic filesystem.
Instead of calling procedures, you model objects into directories
and files and simply work with common filesystem operations.
This is the same idea as behind procfs or sysfs, but on an
distributed level.


Hopefully, we agree that procfs and sysfs are a simple and easy
approach for accessing many many kernel-internal data using
very standard filesystem operations. Now imagine we hadn't them,
but needed to use separate syscalls or netlink operations. Wouldn't
it be ugly ?

> given that plumber is a basic element of 9p and
> does essentially the same job D-Bus does.

No, plumber is an 9P-based service which does the message
broadcasting/routing to listeners (easily programmable by an
special-purpose language). Since it's based on 9P, it can be used
anywhere 9P is available, fully platform independent and network
agnostic.

http://plan9.bell-labs.com/sys/doc/plumb.html



cu
--
----------------------------------------------------------------------
Enrico Weigelt, metux IT service -- http://www.metux.de/

cellphone: +49 174 7066481 email: info@metux.de skype: nekrad666
----------------------------------------------------------------------
Embedded-Linux / Portierung / Opensource-QM / Verteilte Systeme
----------------------------------------------------------------------
 

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