lkml.org 
[lkml]   [2021]   [Mar]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v3 3/5] mm,memory_hotplug: Add kernel boot option to enable memmap_on_memory
From
Date
On 04.03.21 11:00, Oscar Salvador wrote:
> Self stored memmap leads to a sparse memory situation which is unsuitable
> for workloads that requires large contiguous memory chunks, so make this
> an opt-in which needs to be explicitly enabled.
>
> To control this, let memory_hotplug have its own memory space, as suggested
> by David, so we can add memory_hotplug.memmap_on_memory parameter.
>
> Signed-off-by: Oscar Salvador <osalvador@suse.de>
> ---
> Documentation/admin-guide/kernel-parameters.txt | 14 ++++++++++++++
> mm/Makefile | 5 ++++-
> mm/memory_hotplug.c | 8 +++++++-
> 3 files changed, 25 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 04545725f187..e626dab39c60 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2794,6 +2794,20 @@
> seconds. Use this parameter to check at some
> other rate. 0 disables periodic checking.
>
> + memory_hotplug.memmap_on_memory
> + [KNL,X86,ARM] Boolean flag to enable this feature.

Right now it can be set on any arch with memory hotplug, right? It's
simply not effective.

> + Format: {on | off (default)}
> + When enabled, memory to build the pages tables for the
> + memmap array describing the hot-added range will be taken
> + from the range itself, so the memmap page tables will be
> + self-hosted.
> + Since only single memory device ranges are supported at
> + the moment, this option is disabled by default because
> + it might have an impact on workloads that needs large
> + contiguous memory chunks.
> + The state of the flag can be read in
> + /sys/module/memory_hotplug/parameters/memmap_on_memory.

Maybe want to add that even if enabled, there are cases where it is not
effective?

> +
> memtest= [KNL,X86,ARM,PPC] Enable memtest
> Format: <integer>
> default : 0 <disable>
> diff --git a/mm/Makefile b/mm/Makefile
> index 72227b24a616..82ae9482f5e3 100644
> --- a/mm/Makefile
> +++ b/mm/Makefile
> @@ -58,9 +58,13 @@ obj-y := filemap.o mempool.o oom_kill.o fadvise.o \
> page-alloc-y := page_alloc.o
> page-alloc-$(CONFIG_SHUFFLE_PAGE_ALLOCATOR) += shuffle.o
>
> +# Give 'memory_hotplug' its own module-parameter namespace
> +memory-hotplug-$(CONFIG_MEMORY_HOTPLUG) += memory_hotplug.o
> +
> obj-y += page-alloc.o
> obj-y += init-mm.o
> obj-y += memblock.o
> +obj-y += $(memory-hotplug-y)
>
> ifdef CONFIG_MMU
> obj-$(CONFIG_ADVISE_SYSCALLS) += madvise.o
> @@ -83,7 +87,6 @@ obj-$(CONFIG_SLUB) += slub.o
> obj-$(CONFIG_KASAN) += kasan/
> obj-$(CONFIG_KFENCE) += kfence/
> obj-$(CONFIG_FAILSLAB) += failslab.o
> -obj-$(CONFIG_MEMORY_HOTPLUG) += memory_hotplug.o
> obj-$(CONFIG_MEMTEST) += memtest.o
> obj-$(CONFIG_MIGRATION) += migrate.o
> obj-$(CONFIG_TRANSPARENT_HUGEPAGE) += huge_memory.o khugepaged.o
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 63e5a0e9a6f3..94b0ec3d2ff2 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -42,7 +42,13 @@
> #include "internal.h"
> #include "shuffle.h"
>
> -static bool memmap_on_memory;
> +
> +/*
> + * memory_hotplug.memmap_on_memory parameter
> + */
> +static bool memmap_on_memory __ro_after_init;
> +module_param(memmap_on_memory, bool, 0444);
> +MODULE_PARM_DESC(memmap_on_memory, "Enable memmap on memory for memory hotplug");
>

Wondering if this makes sense getting wrapped in

#ifdef CONFIG MHP_MEMMAP_ON_MEMORY

just a thought.

LGTM

Reviewed-by: David Hildenbrand <david@redhat.com>

--
Thanks,

David / dhildenb

\
 
 \ /
  Last update: 2021-03-05 16:36    [W:0.545 / U:0.476 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site