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

[Mel Gorman <mgorman@techsingularity.net>]

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

Acked-by: Mel Gorman <mgorman@techsingularity.net>

-- 
Mel Gorman
SUSE Labs