Compressed Cache for NetBSD

[v***@andrew.cmu.edu]

Hi,

I am a Masters student at Carnegie Mellon University specializing in
Systems (with special emphasis on Operating Systems and Storage Systems).
I have taken a class called Operating Systems Practicum
(https://www.cs.cmu.edu/~412/syllabus.html). The main objective of the
course is to add a feature to any Open Source systems-y product
(preferably an operating systems).

I was browsing through NetBSD project wiki and came across this really
interesting project of Compressed Cache
(http://wiki.netbsd.org/projects/project/compressed-cache/). I would
really appreciate if I could get some insights on this project status. I
will mostly be working alone on this project and the timeframe I have is
around 2 months.

I did some basic reading and have figured out that one approach to
implement this is to have a block device backed by kernel reserved memory.
This block device can used as a staging area for the compressed pages. The
interface can itself be provided through a VFS read/write semantics.

I would really appreciate if I could get any pointers and help on this
project. Eagerly awaiting a response.

Thanks and Regards,
Vinay

[David Holland]

Post by v***@andrew.cmu.edu
I am a Masters student at Carnegie Mellon University specializing in
Systems (with special emphasis on Operating Systems and Storage Systems).
I have taken a class called Operating Systems Practicum
(https://www.cs.cmu.edu/~412/syllabus.html). The main objective of the
course is to add a feature to any Open Source systems-y product
(preferably an operating systems).
I was browsing through NetBSD project wiki and came across this really
interesting project of Compressed Cache
(http://wiki.netbsd.org/projects/project/compressed-cache/). I would
really appreciate if I could get some insights on this project status. I
will mostly be working alone on this project and the timeframe I have is
around 2 months.
I did some basic reading and have figured out that one approach to
implement this is to have a block device backed by kernel reserved memory.
This block device can used as a staging area for the compressed pages. The
interface can itself be provided through a VFS read/write semantics.
I would really appreciate if I could get any pointers and help on this
project. Eagerly awaiting a response.

I don't think anyone's already working on this.

Doing it with a block device (like the referenced Linux code)
shouldn't be all that difficult and even without much background
getting it done in a couple months is probably doable.

The drawback of doing it as a block device that you swap to is that
only anonymous memory pages will be sent to it; pages from files
(which includes e.g. program text) won't. But maybe that's good
enough; apparently the Linux world thought so.

(But don't try doing it inside uvm -- that is not a beginner project...)