Adding ZSwap to kernel

Toast · 10 May 2020 06:00

So ive messed around with zswap and found that the rpi kernel devs might be merging it this would help those that want/need swap like the older rpi1 and zero also for me that love that to have that little extra if and when i need it.

github.com/raspberrypi/linux

RFC: Test of zswap deferred initialisation

raspberrypi:rpi-4.19.y ← pelwell:zswaptest

opened 04:01PM - 05 May 20 UTC

pelwell

+0 -0

This PR is the result of some experimentation to try and defer the cost of enab…ling the ZSWAP configuration option until zswap is actually enabled. There is no guarantee it will get merged, but some feedback that zswap still works and that the overhead is acceptable would make it more likely. See also the discussion at https://github.com/raspberrypi/linux/pull/3432. [ From the first commit message ] ``` Enabling zswap support in the kernel configuration costs about 1.5MB of RAM, even when zswap is not enabled at runtime. This cost can be reduced significantly by deferring initialisation (including pool creation) until the "enabled" parameter is set to true. There is a small cost to this in that some __init functions have to remain in memory after the init phase, just in case they are needed later, but the total size is negligible. ```

any plans for OSMC to support this in the kernel ?

sam_nazarko · 10 May 2020 13:12

It looks like ZSwap is already supported. The PR above just changes how it is initialised

I don’t think there is an application for it for OSMC.

Toast · 10 May 2020 13:24

Zswap isnt available on RPI kernel, same as swap either you need it or you dont and with emulation you kinda need i, when getting to the more demanding roms

sam_nazarko · 10 May 2020 13:42

It definitely exists for 4.19; but we don’t build it in as there’s no use for it presently.

Toast · 10 May 2020 14:47

fair enough i can always go with zram-config since it allow me to do the same thing without zswap module in the kernel just thought it wasnt a big deal to include.