Thread: [ANNOUNCE] COMPCACHE on kernel-power (now with notifications)
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maacruz is offline maacruz
2011-09-10 , 10:44
Posts: 1,101 | Thanked: 1,185 times | Joined on Aug 2008 @ Spain
#131
Originally Posted by freemangordon View Post
Should be posible, but I don't think we will gain anything but additional overhead. You can check upstream zram, they are not using notifications at all, does not seem to have much negative effect. The problem is that SW running on n900 needs lots of RAM and not having it (because it is used by compcache) leads to constant swapping (swap trash).

Anyway there is definitely improvement from using compcahe, just not so much that was probably expected. Use disksize_kb in range 64MB to 96MB and you will see it.
It's really nice that you have finally taken on porting compcache, I was amazed nobody did it for the N900, I did it for the N8x0 and the performance improvement was very noticeable.
In the N8x0 world, having 128 MB of RAM we are using disksize=96 MB by default. As you know, disksize is not the ram used by compcache, having a compression ratio of about 1/3 usually, so in the N8x0 we usually have about 50 MB of swapped ram and 20 MB of ram used for compcache.
So, I find very curious that you are using such a low value when you have 256 MB and a much faster cpu. Really, you should be able to use disksize>128MB with no problems, so may be there is some other cause, may be too much locked ram?
Well, having a look at your sources, I'd recommend to try the same changes I did in ramzswap_drv.h , increase max_zpage_size_nobdev to PAGE_SIZE/8*7, and do not setup a backing device (the code is really inefficient).
 

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