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PostPosted: Tue Mar 20, 2007 2:24 pm 
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Joined: Fri Sep 24, 2004 1:39 am
Posts: 1589
Location: Austin, TX
Any enterprising developers want to see if they can get this to work on PowerPC (Efika being the prime candidate)?

http://linuxcompressed.sourceforge.net/

http://linux-mm.org/CompressedCaching

It is basically a compressed page cache. You trade off a bit of CPU performance (I think the Efika has plenty) for less usage of disk swap space (which is slow on the Efika and will be used too much on a heavy loaded system with low-memory).

It might make GNOME actually usable as a lot of the performance losses I saw was disk thrashing at various points while applications loaded and older ones were paged back out to disk.

I am not sure if it compresses the swap partition too, but it actually might (there was some note about it disabling that feature in an older version, and I didn't see anything about it being re-enabled)

On another note, this interesting article came up today in conversation;

http://hedera.linuxnews.pl/_news/2002/0 ... /1445.html
http://gentoo-wiki.com/TIP_Use_memory_o ... rd_as_swap

The basic idea being to use unused memory on the video card (most Efika users will have 128MB or more..) as swap space using an MTD driver and portioning off an effective amount of space. You could do quite a lot, still, in 32MB of video RAM and let the other 96MB be used to alleviate the low latency and low bandwidth of disk-based swap. The above compression system would help here too.

However in some discussions with kernel developers, there were some drawbacks mentioned - it may be that the console framebuffer (radeonfb, xgifb that sort of thing) may not coexist with it, X may have changed drastically since 2002 (it's an old article!) and certainly it's possible for 3D support (DRI/DRM) to lock the card and effectively disable access to the memory (which would make swapping fail, which is bad).

Since all of this would go a long way to improving user experience on Efika (and ANY embedded system or constrained system) I think they are important projects. Does anyone want to take it on? :)

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Matt Sealey


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PostPosted: Tue Mar 20, 2007 11:53 pm 
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Genesi

Joined: Mon Jan 30, 2006 2:28 am
Posts: 409
Location: Finland
Hi.

I'll give it a try :-)
Sounds interesting enough. The MTD driver should be no problem, too bad it won't work with AIGLX/Beryl (AFAIK).

I'll check out compressed caching too. I'm not using any swap space at the moment but will play around with it.


Best regards,
Johan

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Johan Dams, Genesi USA Inc.
Director, Software Engineering

Yep, I have a blog... PurpleAlienPlanet


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