[ANNOUNCE] COMPCACHE on kernel-power (now with notifications) - maemo.org

freemangordon | # 1 | 2011-08-27, 14:13 | Report

Since version 49 compcache (ramzswap) is a part of kernel-power, the instructions bellow are not needed and shall be used just as a reference

Here is how to make compcache working on n900. You will need scratchbox or madde environment ready for kernel compilation

1. download latest (48) kernel power source in directory of your choice
apt-get source kernel-power

2. unzip and copy attached patches (update_mmu_cache_arm.zip and patch_swap_notify_core_support_2_2.6.28.zip) into kernel-power-2.6.28\debian\patches

3.add update_mmu_cache_arm.diff at the end of series file

cd kernel-power-2.6.28/debian/patches/
echo update_mmu_cache_arm.diff >> series

4.add patch_swap_notify_core_support_2_2.6.28.diff at the end of series file

cd kernel-power-2.6.28/debian/patches/
echo patch_swap_notify_core_support_2_2.6.28.diff >> series

4. goto kernel source directory and build kernel package
dpkg-buildpackage -rfakeroot -b

5. unzip compcache source(compcache-0.6.2.zip) into the same directory you've downloaded kernel sources

6. cd into compcache-0.6.2 and make it

at that point you should have patched kernel .debs and ramzswap.ko for that kernel. Install kernel on the device and copy ramzswap.ko in /lib/modules/2.6.28.10-power48

reboot and use instructions here
in short it is something like

insmod /lib/modules/current/ramzswap.ko disksize_kb=65536
swapon /dev/ramzswap0
swapoff /dev/mmcblk0p3; swapon /dev/mmcblk0p3

Notifications are working, but seems there are paths in the kernel swap subsystem allowing direct write over a page without first marking it free.
Seems like memory consumption should not be affected by that.

I've disabled nokia swap page remapping (for performance reasons), will enable it again if swap fragmentation develops over time to see if it could help.

EDIT: changed recommended disksize_kb to 120512

Attached Files

	update_mmu_cache_arm.zip (492 Bytes, 268 views)
	compcache-0.6.2.zip (34.3 KB, 287 views)
	patch_swap_notify_core_support_2_2.6.28.zip (676 Bytes, 246 views)

Last edited by freemangordon; 2012-05-28 at 05:15.

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jormartr | # 2 | 2011-08-27, 14:50 | Report

Is there any other way for people who can not compile for any other reason? Any precompiled debs, tars or anything?

Thank you, really.

freemangordon | # 3 | 2011-08-27, 14:53 | Report

Originally Posted by jormartr View Post

Is there any other way for people who can not compile for any other reason? Any precompiled debs, tars or anything?

Thank you, really.

kernel debs are too big to be attached here. if you advice on where to upload them i will

neboja | # 4 | 2011-08-27, 15:13 | Report

ok... i'm kinda idiot for this things, but i googled a little bit, so i saw what compcashe is... but, for what is benefit for us? and is it necessary for me to have it?

freemangordon | # 5 | 2011-08-27, 15:22 | Report

Originally Posted by neboja View Post

ok... i'm kinda idiot for this things, but i googled a little bit, so i saw what compcashe is... but, for what is benefit for us? and is it necessary for me to have it?

One of the major hardware limitations n900 has is the amount of RAM. Compcache uses part of this RAM to provide swap space which is expected to be twice as big as the RAM used. i.e. for 128MB swap expected usage is about 50-70 MB. so we win about 60 MB of swap which is extremely fast compared to swap on internal flash. So in short this is expected to reduce lagging under memory pressure.

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jormartr | # 6 | 2011-08-27, 15:23 | Report

Originally Posted by neboja View Post

ok... i'm kinda idiot for this things, but i googled a little bit, so i saw what compcashe is... but, for what is benefit for us? and is it necessary for me to have it?

With compcache you use part of your RAM memory as if it was a compressed SWAP file.

This way, when you are out of memory, instead of using a swap on disk, you use a swap on memory, that is faster. Even with having to sacrify ram for swap, and even compress the swap, you still gain speed by not having to access to disk.

And I hope this is what it will happen with this patch.

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freemangordon | # 7 | 2011-08-27, 15:27 | Report

Pre-compiled binaries in first post

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jormartr | # 8 | 2011-08-27, 16:41 | Report

Omaigaaaaad, nobody comments on this?? The forum and my n900 is about to implosion, finally compcache!!

Haha, joking, I am waiting for some experiences comments, I can not test it myself until middle on next month :/, I really hope this may bring significative improvement.

neboja | # 9 | 2011-08-27, 17:32 | Report

thanks for answers!
so to use it, we must install debs from the first post... right??? or it will be compiled maybe in the next kernel version, so to wait for update??? what do you recommend?
thx for advise

Seker_94 | # 10 | 2011-08-27, 17:36 | Report

freemangordon what will this do to our N900 ?