From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Subject: mm: disable NUMA_BALANCING_DEFAULT_ENABLED and TRANSPARENT_HUGEPAGE on PREEMPT_RT 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@xxxxxxxxxxxxxxxxxxx/ Link: https://lore.kernel.org/all/20211026165100.ahz5bkx44lrrw5pt@xxxxxxxxxxxxx/ Link: https://lkml.kernel.org/r/20211028143327.hfbxjze7palrpfgp@xxxxxxxxxxxxx Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- init/Kconfig | 2 +- mm/Kconfig | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) --- a/init/Kconfig~mm-disable-numa_balancing_default_enabled-and-transparent_hugepage-on-preempt_rt +++ a/init/Kconfig @@ -901,7 +901,7 @@ config NUMA_BALANCING bool "Memory placement aware NUMA scheduler" depends on ARCH_SUPPORTS_NUMA_BALANCING depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY - depends on SMP && NUMA && MIGRATION + depends on SMP && NUMA && MIGRATION && !PREEMPT_RT help This option adds support for automatic NUMA aware memory/task placement. The mechanism is quite primitive and is based on migrating memory when --- a/mm/Kconfig~mm-disable-numa_balancing_default_enabled-and-transparent_hugepage-on-preempt_rt +++ a/mm/Kconfig @@ -371,7 +371,7 @@ config NOMMU_INITIAL_TRIM_EXCESS config TRANSPARENT_HUGEPAGE bool "Transparent Hugepage Support" - depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE + depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE && !PREEMPT_RT select COMPACTION select XARRAY_MULTI help _
