mm, memory-hotpulg: Rename movablenode boot option to movable_node

PATCH In review Zhang Yanfei 3 participants 3 messages Sep 30, 2013 – Oct 1, 2013

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Memory management Documentation MM core Memory hot(un)plug

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Zhang Yanfei

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2013-09-30 17:41 UTC #0 lore raw

PATCH 1/1 mm, memory-hotpulg: Rename movablenode boot option to movable_node

From: Zhang Yanfei <[email protected]>

Since we already has config MOVABLE_NODE, and the boot option movablenode is introduced as the boot-time switch to disable the effects of CONFIG_MOVABLE_NODE=y when the system is booting.

So rename boot option movablenode to movable_node to match the config MOVABLE_NODE. And also updates the description of MOVABLE_NODE in mm/Kconfig and the description of movable_node in kernel doc.

Signed-off-by Zhang Yanfei <[email protected]>

---
 Documentation/kernel-parameters.txt |   16 ++--------------
 mm/Kconfig                          |   17 ++++++++++++-----
 mm/memory_hotplug.c                 |    6 +++---
 3 files changed, 17 insertions(+), 22 deletions(-)

Documentation/kernel-parameters.txt +2 ~~-14~~

index a87e17e..953a533 100644
@@ -1773,20 +1773,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			that the amount of memory usable for all allocations
 			is not too small.
 
-	movablenode		[KNL,X86] This parameter enables/disables the
-			kernel to arrange hotpluggable memory ranges recorded
-			in ACPI SRAT(System Resource Affinity Table) as
-			ZONE_MOVABLE. And these memory can be hot-removed when
-			the system is up.
-			By specifying this option, all the hotpluggable memory
-			will be in ZONE_MOVABLE, which the kernel cannot use.
-			This will cause NUMA performance down. For users who
-			care about NUMA performance, just don't use it.
-			If all the memory ranges in the system are hotpluggable,
-			then the ones used by the kernel at early time, such as
-			kernel code and data segments, initrd file and so on,
-			won't be set as ZONE_MOVABLE, and won't be hotpluggable.
-			Otherwise the kernel won't have enough memory to boot.
+	movable_node	[KNL,X86] Boot-time switch to disable the effects
+			of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
 
 	MTD_Partition=	[MTD]
 			Format: <name>,<region-number>,<size>,<offset>

mm/Kconfig +12 -5

index ff6e820..8d4ebb0 100644
@@ -153,11 +153,18 @@ config MOVABLE_NODE
 	help
 	  Allow a node to have only movable memory.  Pages used by the kernel,
 	  such as direct mapping pages cannot be migrated.  So the corresponding
-	  memory device cannot be hotplugged.  This option allows users to
-	  online all the memory of a node as movable memory so that the whole
-	  node can be hotplugged.  Users who don't use the memory hotplug
-	  feature are fine with this option on since they don't online memory
-	  as movable.
+	  memory device cannot be hotplugged.  This option allows the following
+	  two things:
+	  - When the system is booting, node full of hotpluggable memory can
+	  be arranged to have only movable memory so that the whole node can
+	  be hotplugged. (need movable_node boot option specified).
+	  - After the system is up, the option allows users to online all the
+	  memory of a node as movable memory so that the whole node can be
+	  hotplugged.
+
+	  Users who don't use the memory hotplug feature are fine with this
+	  option on since they don't specify movable_node boot option or they
+	  don't online memory as movable.
 
 	  Say Y here if you want to hotplug a whole node.
 	  Say N here if you want kernel to use memory on all nodes evenly.

mm/memory_hotplug.c +3 -3

index b468f77..5e2aed9 100644
@@ -1424,7 +1424,7 @@ static bool can_offline_normal(struct zone *zone, unsigned long nr_pages)
 }
 #endif /* CONFIG_MOVABLE_NODE */
 
-static int __init cmdline_parse_movablenode(char *p)
+static int __init cmdline_parse_movable_node(char *p)
 {
 #ifdef CONFIG_MOVABLE_NODE
 	/*

@@ -1448,11 +1448,11 @@ static int __init cmdline_parse_movablenode(char *p)
 	 */
 	memblock_set_bottom_up(true);
 #else
-	pr_warn("movablenode option not supported");
+	pr_warn("movable_node option not supported");
 #endif
 	return 0;
 }
-early_param("movablenode", cmdline_parse_movablenode);
+early_param("movable_node", cmdline_parse_movable_node);
 
 /* check which state of node_states will be changed when offline memory */
 static void node_states_check_changes_offline(unsigned long nr_pages,

Signature · 7 lines

1.7.1

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Ingo Molnar

2013-10-01 05:46 UTC #1 lore raw

mm/Kconfig config MOVABLE_NODE · line 160

Quoted 9 lines · Zhang Yanfei

mm/Kconfig +5 -0

@@ -153,11 +153,18 @@ config MOVABLE_NODE
 	help
 	  Allow a node to have only movable memory.  Pages used by the kernel,
 	  such as direct mapping pages cannot be migrated.  So the corresponding
+	  memory device cannot be hotplugged.  This option allows the following
+	  two things:
+	  - When the system is booting, node full of hotpluggable memory can
+	  be arranged to have only movable memory so that the whole node can
+	  be hotplugged. (need movable_node boot option specified).

So this is _exactly_ what I complained about earlier: why is the movable_node boot option needed to get that extra functionality? It's clearly not just a drop-in substitute to CONFIG_MOVABLE_NODE but extends its functionality, right?

Boot options are _very_ poor user interface. If you don't want to enable it by default then turn this sub-functionality into CONFIG_MOVABLE_NODE_AUTO and keep it default-off - but don't pretend that this is only about CONFIG_MOVABLE_NODE alone - it isnt: as described above the 'movable_node' is needed for the full functionality to be available!

Thanks,

Ingo

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Zhang Yanfei

2013-10-01 06:22 UTC #2 lore raw

Hello Ingo,

Quoted 17 lines · Ingo Molnar

mm/Kconfig config MOVABLE_NODE · line 160
Quoted 9 lines · Zhang Yanfei
mm/Kconfig +5 -0
@@ -153,11 +153,18 @@ config MOVABLE_NODE
 	help
 	  Allow a node to have only movable memory.  Pages used by the kernel,
 	  such as direct mapping pages cannot be migrated.  So the corresponding
+	  memory device cannot be hotplugged.  This option allows the following
+	  two things:
+	  - When the system is booting, node full of hotpluggable memory can
+	  be arranged to have only movable memory so that the whole node can
+	  be hotplugged. (need movable_node boot option specified).
So this is _exactly_ what I complained about earlier: why is the movable_node boot option needed to get that extra functionality? It's clearly not just a drop-in substitute to CONFIG_MOVABLE_NODE but extends its functionality, right?

Generally speaking, CONFIG_MOVABLE_NODE is used to allow a node to have only movable memory. Firstly, we didn't support the functionality to support boot-time configuration. That said, before this patchset, we only support later hot-add node to have only movable memory but any node that is dectected at boot-time cannot. So here is movable_node option, to protect the kernel from using hotpluggable memory at boot-time and if a node is full of hotpluggable memory, this node is arranged to have only movable memory and can be hot-removed after the system is up.

Quoted 6 lines

Boot options are _very_ poor user interface. If you don't want to enable it by default then turn this sub-functionality into CONFIG_MOVABLE_NODE_AUTO and keep it default-off - but don't pretend that this is only about CONFIG_MOVABLE_NODE alone - it isnt: as described above the 'movable_node' is needed for the full functionality to be available!

As explained above, we need the boot option to only disable boot-time memory-hotplug configuration not the whole MOVABLE_NODE functionality.

Thanks

Signature · 2 lines

Thanks.
Zhang Yanfei