[maemo-developers] [maemo-developers] Installing packages in extra storage?

[From: Dieter Govaerts]

Hi Gustavo,

Gustavo Sverzut Barbieri schreef:
> Hello,
> 
> Is it possible to install software on extra storage, like MMC or some
> other kind of share (smb, nfs, ...)?
> 
> Nokia 770 with just 64Mb may raise some problems and we must have
> platform support for this feature. If this feature is not available I
> will write a enhancement proposal and try to implement it.
> 

I'm currently working on my master thesis which is a research project to 
examine the possibilities of a solution to this very same problem. The 
idea is to use some sort of streaming technique for applications on a 
remote server and do some caching of the remote applications on the 
local device.

A quick overview of the system:
1) Upon first activation of an application by the user, a small 
installation package is transferred to the device form the remote 
server, containing installation scripts and a list of files used by the 
application. The package contains no files from the application itself, 
only setup-files.
2) The application is installed on the local device and the 
application’s files are added to the caching file system but the files 
remain empty for now.
3) All the application’s files are stored on the remote server and are 
split-up and made available as individual memory pages.
4) When the application starts running, the operating system begins to 
receive page faults. For each page fault, the caching file system is 
asked to provide the application code to be loaded into memory. The 
caching file system checks if it has a local copy available and if not, 
requests it from the remote server.

Pros to this approach:
* Only the used parts of an application are downloaded, a user almost 
never uses the complete functionality of an application. This saves 
initial bandwidth usage and local storage.
* Since only the used parts of an application are cached locally, more 
space remains to cache the used parts of other applications.
* Since the installation of an application only involves adding empty 
files to the caching file system, and starting that the application for 
the first time involves downloading a few application code pages, a user 
is able to use his new application much faster.

Cons to this approach:
* That’s what my research project is all about :-). But some may include:
* High bandwidth usage when too many applications are cached due to 
eviction of used pages from the cache.
* Reduced user experience due to increased latency when using uncached 
features of an application.

I’m currently still in the research phase for this system. Design and 
implementation of a prototype system starts in February. Any ideas, 
suggestions or hints regarding architecture, design or implementation 
(mainly about the local caching part and ‘fooling’ the operating system 
with those cached files), or information about existing projects that 
can be used in my project, are greatly appreciated.

Best regards,

Dieter Govaerts

--
Student Computer Engineering
at the University of Ghent (Belgium)
dieter.govaerts(at)ugent.be