Re: [PATCH] mm: Disable NUMA_BALANCING_DEFAULT_ENABLED and TRANSPARENT_HUGEPAGE on PREEMPT_RT

On Thu, Oct 28, 2021 at 04:33:27PM +0200, Sebastian Andrzej Siewior wrote:

TRANSPARENT_HUGEPAGE:
There are potential non-deterministic delays to an RT thread if a critical
memory region is not THP-aligned and a non-RT buffer is located in the same
hugepage-aligned region. It's also possible for an unrelated thread to migrate
pages belonging to an RT task incurring unexpected page faults due to memory
defragmentation even if khugepaged is disabled.

Regular HUGEPAGEs are not affected by this can be used.

NUMA_BALANCING:
There is a non-deterministic delay to mark PTEs PROT_NONE to gather NUMA fault
samples, increased page faults of regions even if mlocked and non-deterministic
delays when migrating pages.

[Mel Gorman worded 99% of the commit description].

Link: https://lore.kernel.org/all/20200304091159.GN3818@techsingularity.net/ (local)
Link: https://lore.kernel.org/all/20211026165100.ahz5bkx44lrrw5pt@linutronix.de/ (local)
Cc: Mel Gorman <redacted>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Acked-by: Mel Gorman <redacted>

-- 
Mel Gorman
SUSE Labs