On Mon, 14 Feb 2022 15:27:36 +0100, Joe Salmeri wrote:

If I run cat /boot/config-5.16.1-1-default | grep -i swap

It returns CONFIG_ZSWAP=Y

cat /sys/module/zswap/parameters/enabled returns N

So the kernel supports zswap but it is currently NOT enabled.

When system is booted the following journal message appears

kernel: zswap: loaded using pool lzo/zbud

ps aux | grep -i zswap

returns

root 135 0.0 0.0 0 0 ? I< Feb09 0:00 [zswap-shrink]

If zswap is NOT enabled, why is zswap loaded with a pool at boot time and why is the zswap-shrink process running?

I find that the same situation on a TW test machine I have that is running the 5.16.5.2 kernel so it is not an isolated case.

Is this a bug?

The zswap's enabled sysfs can be toggled dynamically even after the boot, which enables/disables the zswp on the fly. Meanwhile the kconfig specifies whether zswap is supported or not at all. So this is expected behavior. zswap-shrink is a kernel workqueue, and it's idle unless a work is queued there. It consumes some memory, but that's all. Takashi