This is ready for a Wiki entry. If you provide me with your findings summary, i could do it.

thanks you my friends!
let see the performance now, by the way mine is class 10 16GB sd card, maybe have more gd performance

I now confirmed use microsd have better performance than internal swap

i think that is confirmed years ago

my question is : DOES COMPCACHE IMPROVE ANYTHING ??!!?!!
IN MY CASE nothing

Having a disksize of 64MB, and a swap of 512MB, with the disk made on startup, it keeps everything as snappy as it is. No slowdowns at all, even after an extended amount of time.

Cannot disagree with you.

About swap on SD-card. Has somebody tested impact to battery (standby time, etc...) comparing swap on eMMC vs SD?

eMMC is 1.8v interface, but SD card signals needs to go thru levelshifter + filtering component, which increase load capacitance on this interface (IC 1.8v <-> 3.0v SD-card). In practice it means more (peak)current taken from battery (incl. 3v regulator) to drive card/levelshifter.

Also swap on SD-card require that interface must be active all the time.

Q: Is there real benefit to have swap on SD-card?

@Gusse,

That's a really good question/observation

I've only started using swap on SD (only, no striping) a few days ago. Cannot really tell if performance is better (perhaps a bit, but I may have been subjectively biased..).

So far I have not noticed any difference in battery life/consumption, but it's been only three days..

I'll try to keep an eye on this and maybe do a test or two..

Without changing IO scheduler settings there is no reason to expect much improvement. While with correct values the lady performs like a beast both under high memory pressure and high IO load.

Rationale for swap on microSD is IMO avoiding I/O conflicts with other eMMC requests. I'm using it for months now, and for me, it's a must-have. Yea, You may not notice difference in day-to-day use, but under high I/O + high swap usage, You'll feel it Sometimes, to the point of crash (without swap on microSD), as Easy Debian thread prove.

As for battery usage, I don't see any real life higher usage. In terms of both subjective feeling, and "scientific" measurements (average current tracking). I think mounted SD card is somehow "always in use" in terms of interfaces power usage etc. It's also possible that I'm wrong here, but impact on battery life is close to 0 anyway

How is one supposed to get this working with multiboot? When I installed the debs with 'sudo dpkg -i *.deb' and copied the module into /lib/modules/2.6.28.10-power48, rebooted, selected kernel power 48 in multiboot, and then ran 'modprobe ramzswap disksize_kb=97280' ( 95MB compcache size), I got a brief error message and then my phone rebooted. I think this is due to the fact that the old kernel power 48 was loaded. If you could supply a kernel-power-bootimg.deb or just the plain boot image I think it would resolve this problem.

I'm probably missing something obvious, so feel free to correct me.

Thanks,

jdb2