linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Oscar Salvador <osalvador@suse.de>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: David Hildenbrand <david@redhat.com>,
	Michal Hocko <mhocko@kernel.org>,
	Anshuman Khandual <anshuman.khandual@arm.com>,
	Pavel Tatashin <pasha.tatashin@soleen.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Oscar Salvador <osalvador@suse.de>,
	Michal Hocko <mhocko@suse.com>
Subject: [PATCH v8 6/8] mm,memory_hotplug: Add kernel boot option to enable memmap_on_memory
Date: Fri, 16 Apr 2021 12:21:51 +0200	[thread overview]
Message-ID: <20210416102153.8794-7-osalvador@suse.de> (raw)
In-Reply-To: <20210416102153.8794-1-osalvador@suse.de>

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>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 17 +++++++++++++++++
 mm/Makefile                                     |  5 ++++-
 mm/memory_hotplug.c                             | 10 +++++++++-
 3 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 04545725f187..af32c17cd4eb 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2794,6 +2794,23 @@
 			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.
+			Format: {on | off (default)}
+			When enabled, runtime hotplugged memory will
+			allocate its internal metadata (struct pages)
+			from the hotadded memory which will allow to
+			hotadd a lot of memory without requiring
+			additional memory to do so.
+			This feature is disabled by default because it
+			has some implication on large (e.g. GB)
+			allocations in some configurations (e.g. small
+			memory blocks).
+			The state of the flag can be read in
+			/sys/module/memory_hotplug/parameters/memmap_on_memory.
+			Note that even when enabled, there are a few cases where
+			the feature 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 7efee41268b6..54c78c486f1f 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -42,7 +42,15 @@
 #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;
+#ifdef CONFIG_MHP_MEMMAP_ON_MEMORY
+module_param(memmap_on_memory, bool, 0444);
+MODULE_PARM_DESC(memmap_on_memory, "Enable memmap on memory for memory hotplug");
+#endif
 
 /*
  * online_page_callback contains pointer to current page onlining function.
-- 
2.16.3


  parent reply	other threads:[~2021-04-16 10:22 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-16 10:21 [PATCH v8 0/8] Allocate memmap from hotadded memory (per device) Oscar Salvador
2021-04-16 10:21 ` [PATCH v8 1/8] drivers/base/memory: Introduce memory_block_{online,offline} Oscar Salvador
2021-04-16 10:21 ` [PATCH v8 2/8] mm,memory_hotplug: Relax fully spanned sections check Oscar Salvador
2021-04-16 10:21 ` [PATCH v8 3/8] mm,memory_hotplug: Factor out adjusting present pages into adjust_present_page_count() Oscar Salvador
2021-04-16 10:21 ` [PATCH v8 4/8] mm,memory_hotplug: Allocate memmap from the added memory range Oscar Salvador
2021-04-16 10:33   ` David Hildenbrand
2021-04-16 10:37     ` Oscar Salvador
2021-04-16 10:51       ` David Hildenbrand
2021-04-16 11:01         ` Oscar Salvador
2021-04-16 11:07           ` David Hildenbrand
2021-04-16 10:21 ` [PATCH v8 5/8] acpi,memhotplug: Enable MHP_MEMMAP_ON_MEMORY when supported Oscar Salvador
2021-04-16 10:21 ` Oscar Salvador [this message]
2021-04-16 10:21 ` [PATCH v8 7/8] x86/Kconfig: Introduce ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE Oscar Salvador
2021-04-16 10:21 ` [PATCH v8 8/8] arm64/Kconfig: " Oscar Salvador

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210416102153.8794-7-osalvador@suse.de \
    --to=osalvador@suse.de \
    --cc=akpm@linux-foundation.org \
    --cc=anshuman.khandual@arm.com \
    --cc=david@redhat.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mhocko@kernel.org \
    --cc=mhocko@suse.com \
    --cc=pasha.tatashin@soleen.com \
    --cc=vbabka@suse.cz \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).