Don't use MADV_RANDOM

[sdodson]

In addition to the explicit documented behavior in posix_madvise(2) this
call since Linux 6.4 also causes the kernel to aggressively free pages
from the page cache by short circuiting the LRU second chance mechanism.
The result is compaction events that took 900ms now take up to 20s and
a system which generally operated with near zero major page faults sees
600 or more major faults per second during compaction events.

We've tested this change in older kernels and observed no negative impact
in typical cloud instances.

Fixes #939

[k8s-ci-robot]

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[k8s-ci-robot]

Hi @sdodson. Thanks for your PR.

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[sdodson]

CC @dusk125

[sdodson]

I'll be revisiting this in the coming months as OpenShift moves to complete our transition to RHEL10 (6.12 baseline kernel). I'm OK with it being closed and would re-open it once I've confirmed that we see high rate of page faults, maybe something else in RHEL10 and/or upstream kernel mitigated the unique behavior seen on RHEL 9 kernels, who knows.