v5 De-couple sysfs memory directories from memory sections

PATCH In review Nathan Fontenot 5 participants 19 messages Aug 9, 2010 – Sep 2, 2010

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Nathan Fontenot

author

2010-08-09 17:53 UTC #0 lore raw

cover v5 De-couple sysfs memory directories from memory sections

This set of patches de-couples the idea that there is a single directory in sysfs for each memory section. The intent of the patches is to reduce the number of sysfs directories created to resolve a boot-time performance issue. On very large systems boot time are getting very long (as seen on powerpc hardware) due to the enormous number of sysfs directories being created. On a system with 1 TB of memory we create ~63,000 directories. For even larger systems boot times are being measured in hours.

This set of patches allows for each directory created in sysfs to cover more than one memory section. The default behavior for sysfs directory creation is the same, in that each directory represents a single memory section. A new file 'end_phys_index' in each directory contains the physical_id of the last memory section covered by the directory so that users can easily determine the memory section range of a directory.

Updates for version 5 of the patchset include the following:

Patch 4/8 Add mutex for add/remove of memory blocks
- Define the mutex using DEFINE_MUTEX macro.

Patch 8/8 Update memory-hotplug documentation
- Add information concerning memory holes in phys_index..end_phys_index.

Thanks,

Nathan Fontenot

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Nathan Fontenot

author

2010-08-09 18:35 UTC #1 lore raw

PATCH 1/8 v5 Move the find_memory_block() routine up

Move the find_me mory_block() routine up to avoid needing a forward declaration in subsequent patches.

Signed-off-by Nathan Fontenot <[email protected]>

---
 drivers/base/memory.c |   62 +++++++++++++++++++++++++-------------------------
 1 file changed, 31 insertions(+), 31 deletions(-)

drivers/base/memory.c +31 ~~-31~~

Index: linux-2.6/drivers/base/memory.c
===================================================================
@@ -435,6 +435,37 @@ int __weak arch_get_memory_phys_device(u
 	return 0;
 }
 
+/*
+ * For now, we have a linear search to go find the appropriate
+ * memory_block corresponding to a particular phys_index. If
+ * this gets to be a real problem, we can always use a radix
+ * tree or something here.
+ *
+ * This could be made generic for all sysdev classes.
+ */
+struct memory_block *find_memory_block(struct mem_section *section)
+{
+	struct kobject *kobj;
+	struct sys_device *sysdev;
+	struct memory_block *mem;
+	char name[sizeof(MEMORY_CLASS_NAME) + 9 + 1];
+
+	/*
+	 * This only works because we know that section == sysdev->id
+	 * slightly redundant with sysdev_register()
+	 */
+	sprintf(&name[0], "%s%d", MEMORY_CLASS_NAME, __section_nr(section));
+
+	kobj = kset_find_obj(&memory_sysdev_class.kset, name);
+	if (!kobj)
+		return NULL;
+
+	sysdev = container_of(kobj, struct sys_device, kobj);
+	mem = container_of(sysdev, struct memory_block, sysdev);
+
+	return mem;
+}
+
 static int add_memory_block(int nid, struct mem_section *section,
 			unsigned long state, enum mem_add_context context)
 {

@@ -468,37 +499,6 @@ static int add_memory_block(int nid, str
 	return ret;
 }
 
-/*
- * For now, we have a linear search to go find the appropriate
- * memory_block corresponding to a particular phys_index. If
- * this gets to be a real problem, we can always use a radix
- * tree or something here.
- *
- * This could be made generic for all sysdev classes.
- */
-struct memory_block *find_memory_block(struct mem_section *section)
-{
-	struct kobject *kobj;
-	struct sys_device *sysdev;
-	struct memory_block *mem;
-	char name[sizeof(MEMORY_CLASS_NAME) + 9 + 1];
-
-	/*
-	 * This only works because we know that section == sysdev->id
-	 * slightly redundant with sysdev_register()
-	 */
-	sprintf(&name[0], "%s%d", MEMORY_CLASS_NAME, __section_nr(section));
-
-	kobj = kset_find_obj(&memory_sysdev_class.kset, name);
-	if (!kobj)
-		return NULL;
-
-	sysdev = container_of(kobj, struct sys_device, kobj);
-	mem = container_of(sysdev, struct memory_block, sysdev);
-
-	return mem;
-}
-
 int remove_memory_block(unsigned long node_id, struct mem_section *section,
 		int phys_device)
 {

Nathan Fontenot

author

2010-08-09 18:36 UTC #2 lore raw

PATCH 2/8 v5 Add new phys_index properties

In reply to Nathan Fontenot

Update the 'phys_index' properties of a memory block to include a 'start_phys_index' which is the same as the current 'phys_index' property. The property still appears as 'phys_index' in sysfs but the memory_block struct name is updated to indicate the start and end values. This also adds an 'end_phys_index' property to indicate the id of the last section in th memory block.

Signed-off-by Nathan Fontenot <[email protected]>

---
 drivers/base/memory.c  |   28 ++++++++++++++++++++--------
 include/linux/memory.h |    3 ++-
 2 files changed, 22 insertions(+), 9 deletions(-)

drivers/base/memory.c +20 -8

Index: linux-2.6/drivers/base/memory.c
===================================================================
@@ -109,12 +109,20 @@ unregister_memory(struct memory_block *m
  * uses.
  */
 
-static ssize_t show_mem_phys_index(struct sys_device *dev,
+static ssize_t show_mem_start_phys_index(struct sys_device *dev,
 			struct sysdev_attribute *attr, char *buf)
 {
 	struct memory_block *mem =
 		container_of(dev, struct memory_block, sysdev);
-	return sprintf(buf, "%08lx\n", mem->phys_index);
+	return sprintf(buf, "%08lx\n", mem->start_phys_index);
+}
+
+static ssize_t show_mem_end_phys_index(struct sys_device *dev,
+			struct sysdev_attribute *attr, char *buf)
+{
+	struct memory_block *mem =
+		container_of(dev, struct memory_block, sysdev);
+	return sprintf(buf, "%08lx\n", mem->end_phys_index);
 }
 
 /*

@@ -128,7 +136,7 @@ static ssize_t show_mem_removable(struct
 	struct memory_block *mem =
 		container_of(dev, struct memory_block, sysdev);
 
-	start_pfn = section_nr_to_pfn(mem->phys_index);
+	start_pfn = section_nr_to_pfn(mem->start_phys_index);
 	ret = is_mem_section_removable(start_pfn, PAGES_PER_SECTION);
 	return sprintf(buf, "%d\n", ret);
 }

@@ -191,7 +199,7 @@ memory_block_action(struct memory_block
 	int ret;
 	int old_state = mem->state;
 
-	psection = mem->phys_index;
+	psection = mem->start_phys_index;
 	first_page = pfn_to_page(psection << PFN_SECTION_SHIFT);
 
 	/*

@@ -264,7 +272,7 @@ store_mem_state(struct sys_device *dev,
 	int ret = -EINVAL;
 
 	mem = container_of(dev, struct memory_block, sysdev);
-	phys_section_nr = mem->phys_index;
+	phys_section_nr = mem->start_phys_index;
 
 	if (!present_section_nr(phys_section_nr))
 		goto out;

@@ -296,7 +304,8 @@ static ssize_t show_phys_device(struct s
 	return sprintf(buf, "%d\n", mem->phys_device);
 }
 
-static SYSDEV_ATTR(phys_index, 0444, show_mem_phys_index, NULL);
+static SYSDEV_ATTR(phys_index, 0444, show_mem_start_phys_index, NULL);
+static SYSDEV_ATTR(end_phys_index, 0444, show_mem_end_phys_index, NULL);
 static SYSDEV_ATTR(state, 0644, show_mem_state, store_mem_state);
 static SYSDEV_ATTR(phys_device, 0444, show_phys_device, NULL);
 static SYSDEV_ATTR(removable, 0444, show_mem_removable, NULL);

@@ -476,16 +485,18 @@ static int add_memory_block(int nid, str
 	if (!mem)
 		return -ENOMEM;
 
-	mem->phys_index = __section_nr(section);
+	mem->start_phys_index = __section_nr(section);
 	mem->state = state;
 	mutex_init(&mem->state_mutex);
-	start_pfn = section_nr_to_pfn(mem->phys_index);
+	start_pfn = section_nr_to_pfn(mem->start_phys_index);
 	mem->phys_device = arch_get_memory_phys_device(start_pfn);
 
 	ret = register_memory(mem, section);
 	if (!ret)
 		ret = mem_create_simple_file(mem, phys_index);
 	if (!ret)
+		ret = mem_create_simple_file(mem, end_phys_index);
+	if (!ret)
 		ret = mem_create_simple_file(mem, state);
 	if (!ret)
 		ret = mem_create_simple_file(mem, phys_device);

@@ -507,6 +518,7 @@ int remove_memory_block(unsigned long no
 	mem = find_memory_block(section);
 	unregister_mem_sect_under_nodes(mem);
 	mem_remove_simple_file(mem, phys_index);
+	mem_remove_simple_file(mem, end_phys_index);
 	mem_remove_simple_file(mem, state);
 	mem_remove_simple_file(mem, phys_device);
 	mem_remove_simple_file(mem, removable);

include/linux/memory.h +2 -1

Index: linux-2.6/include/linux/memory.h
===================================================================
@@ -21,7 +21,8 @@
 #include <linux/mutex.h>
 
 struct memory_block {
-	unsigned long phys_index;
+	unsigned long start_phys_index;
+	unsigned long end_phys_index;
 	unsigned long state;
 	/*
 	 * This serializes all state change requests.  It isn't

Nathan Fontenot

author

2010-08-09 18:37 UTC #3 lore raw

PATCH 3/8 v5 Add section count to memory_block

In reply to Nathan Fontenot

Add a section count property to the memory_block struct to track the number of memory sections that have been added/removed from a memory block. This alolws us to know when the lasat memory section of a memory block has been removed so we can remove the memory block.

Signed-off-by Nathan Fontenot <[email protected]>

---
 drivers/base/memory.c  |   18 +++++++++++-------
 include/linux/memory.h |    2 ++
 2 files changed, 13 insertions(+), 7 deletions(-)

drivers/base/memory.c +11 -7

Index: linux-2.6/drivers/base/memory.c
===================================================================
@@ -487,6 +487,7 @@ static int add_memory_block(int nid, str
 
 	mem->start_phys_index = __section_nr(section);
 	mem->state = state;
+	atomic_inc(&mem->section_count);
 	mutex_init(&mem->state_mutex);
 	start_pfn = section_nr_to_pfn(mem->start_phys_index);
 	mem->phys_device = arch_get_memory_phys_device(start_pfn);

@@ -516,13 +517,16 @@ int remove_memory_block(unsigned long no
 	struct memory_block *mem;
 
 	mem = find_memory_block(section);
-	unregister_mem_sect_under_nodes(mem);
-	mem_remove_simple_file(mem, phys_index);
-	mem_remove_simple_file(mem, end_phys_index);
-	mem_remove_simple_file(mem, state);
-	mem_remove_simple_file(mem, phys_device);
-	mem_remove_simple_file(mem, removable);
-	unregister_memory(mem, section);
+
+	if (atomic_dec_and_test(&mem->section_count)) {
+		unregister_mem_sect_under_nodes(mem);
+		mem_remove_simple_file(mem, phys_index);
+		mem_remove_simple_file(mem, end_phys_index);
+		mem_remove_simple_file(mem, state);
+		mem_remove_simple_file(mem, phys_device);
+		mem_remove_simple_file(mem, removable);
+		unregister_memory(mem, section);
+	}
 
 	return 0;
 }

include/linux/memory.h +2 -0

Index: linux-2.6/include/linux/memory.h
===================================================================
@@ -19,11 +19,13 @@
 #include <linux/node.h>
 #include <linux/compiler.h>
 #include <linux/mutex.h>
+#include <asm/atomic.h>
 
 struct memory_block {
 	unsigned long start_phys_index;
 	unsigned long end_phys_index;
 	unsigned long state;
+	atomic_t section_count;
 	/*
 	 * This serializes all state change requests.  It isn't
 	 * held during creation because the control files are

Nathan Fontenot

author

2010-08-09 18:38 UTC #4 lore raw

PATCH 4/8 v5 Add mutex for add/remove of memory blocks

In reply to Nathan Fontenot

Add a new mutex for use in adding and removing of memory blocks. This is needed to avoid any race conditions in which the same memory block could be added and removed at the same time.

Signed-off-by Nathan Fontenot <[email protected]>

---
 drivers/base/memory.c |    7 +++++++
 1 file changed, 7 insertions(+)

drivers/base/memory.c +7 -0

Index: linux-2.6/drivers/base/memory.c
===================================================================
@@ -27,6 +27,8 @@
 #include <asm/atomic.h>
 #include <asm/uaccess.h>
 
+static DEFINE_MUTEX(mem_sysfs_mutex);
+
 #define MEMORY_CLASS_NAME	"memory"
 
 static struct sysdev_class memory_sysdev_class = {

@@ -485,6 +487,8 @@ static int add_memory_block(int nid, str
 	if (!mem)
 		return -ENOMEM;
 
+	mutex_lock(&mem_sysfs_mutex);
+
 	mem->start_phys_index = __section_nr(section);
 	mem->state = state;
 	atomic_inc(&mem->section_count);

@@ -508,6 +512,7 @@ static int add_memory_block(int nid, str
 			ret = register_mem_sect_under_node(mem, nid);
 	}
 
+	mutex_unlock(&mem_sysfs_mutex);
 	return ret;
 }

@@ -516,6 +521,7 @@ int remove_memory_block(unsigned long no
 {
 	struct memory_block *mem;
 
+	mutex_lock(&mem_sysfs_mutex);
 	mem = find_memory_block(section);
 
 	if (atomic_dec_and_test(&mem->section_count)) {

@@ -528,6 +534,7 @@ int remove_memory_block(unsigned long no
 		unregister_memory(mem, section);
 	}
 
+	mutex_unlock(&mem_sysfs_mutex);
 	return 0;
 }

Nathan Fontenot

author

2010-08-09 18:40 UTC #5 lore raw

PATCH 5/8 v5 Allow memory_block to span multiple memory sections

In reply to Nathan Fontenot

Update the memory sysfs code that each sysfs memory directory is now considered a memory block that can contain multiple memory sections per memory block. The default size of each memory block is SECTION_SIZE_BITS to maintain the current behavior of having a single memory section per memory block (i.e. one sysfs directory per memory section).

For architectures that want to have memory blocks span multiple memory sections they need only define their own memory_block_size_bytes() routine.

Signed-off-by Nathan Fontenot <[email protected]>

---
 drivers/base/memory.c |  148 ++++++++++++++++++++++++++++++++++----------------
 1 file changed, 103 insertions(+), 45 deletions(-)

drivers/base/memory.c +103 ~~-45~~

Index: linux-2.6/drivers/base/memory.c
===================================================================
@@ -30,6 +30,14 @@
 static DEFINE_MUTEX(mem_sysfs_mutex);
 
 #define MEMORY_CLASS_NAME	"memory"
+#define MIN_MEMORY_BLOCK_SIZE	(1 << SECTION_SIZE_BITS)
+
+static int sections_per_block;
+
+static inline int base_memory_block_id(int section_nr)
+{
+	return (section_nr / sections_per_block) * sections_per_block;
+}
 
 static struct sysdev_class memory_sysdev_class = {
 	.name = MEMORY_CLASS_NAME,

@@ -84,22 +92,21 @@ EXPORT_SYMBOL(unregister_memory_isolate_
  * register_memory - Setup a sysfs device for a memory block
  */
 static
-int register_memory(struct memory_block *memory, struct mem_section *section)
+int register_memory(struct memory_block *memory)
 {
 	int error;
 
 	memory->sysdev.cls = &memory_sysdev_class;
-	memory->sysdev.id = __section_nr(section);
+	memory->sysdev.id = memory->start_phys_index;
 
 	error = sysdev_register(&memory->sysdev);
 	return error;
 }
 
 static void
-unregister_memory(struct memory_block *memory, struct mem_section *section)
+unregister_memory(struct memory_block *memory)
 {
 	BUG_ON(memory->sysdev.cls != &memory_sysdev_class);
-	BUG_ON(memory->sysdev.id != __section_nr(section));
 
 	/* drop the ref. we got in remove_memory_block() */
 	kobject_put(&memory->sysdev.kobj);

@@ -133,13 +140,16 @@ static ssize_t show_mem_end_phys_index(s
 static ssize_t show_mem_removable(struct sys_device *dev,
 			struct sysdev_attribute *attr, char *buf)
 {
-	unsigned long start_pfn;
-	int ret;
+	unsigned long i, pfn;
+	int ret = 1;
 	struct memory_block *mem =
 		container_of(dev, struct memory_block, sysdev);
 
-	start_pfn = section_nr_to_pfn(mem->start_phys_index);
-	ret = is_mem_section_removable(start_pfn, PAGES_PER_SECTION);
+	for (i = mem->start_phys_index; i <= mem->end_phys_index; i++) {
+		pfn = section_nr_to_pfn(i);
+		ret &= is_mem_section_removable(pfn, PAGES_PER_SECTION);
+	}
+
 	return sprintf(buf, "%d\n", ret);
 }

@@ -192,17 +202,14 @@ int memory_isolate_notify(unsigned long
  * OK to have direct references to sparsemem variables in here.
  */
 static int
-memory_block_action(struct memory_block *mem, unsigned long action)
+memory_section_action(unsigned long phys_index, unsigned long action)
 {
 	int i;
-	unsigned long psection;
 	unsigned long start_pfn, start_paddr;
 	struct page *first_page;
 	int ret;
-	int old_state = mem->state;
 
-	psection = mem->start_phys_index;
-	first_page = pfn_to_page(psection << PFN_SECTION_SHIFT);
+	first_page = pfn_to_page(phys_index << PFN_SECTION_SHIFT);
 
 	/*
 	 * The probe routines leave the pages reserved, just

@@ -215,8 +222,8 @@ memory_block_action(struct memory_block
 				continue;
 
 			printk(KERN_WARNING "section number %ld page number %d "
-				"not reserved, was it already online? \n",
-				psection, i);
+				"not reserved, was it already online?\n",
+				phys_index, i);
 			return -EBUSY;
 		}
 	}

@@ -227,18 +234,13 @@ memory_block_action(struct memory_block
 			ret = online_pages(start_pfn, PAGES_PER_SECTION);
 			break;
 		case MEM_OFFLINE:
-			mem->state = MEM_GOING_OFFLINE;
 			start_paddr = page_to_pfn(first_page) << PAGE_SHIFT;
 			ret = remove_memory(start_paddr,
 					    PAGES_PER_SECTION << PAGE_SHIFT);
-			if (ret) {
-				mem->state = old_state;
-				break;
-			}
 			break;
 		default:
-			WARN(1, KERN_WARNING "%s(%p, %ld) unknown action: %ld\n",
-					__func__, mem, action, action);
+			WARN(1, KERN_WARNING "%s(%ld, %ld) unknown action: "
+			     "%ld\n", __func__, phys_index, action, action);
 			ret = -EINVAL;
 	}

@@ -248,7 +250,7 @@ memory_block_action(struct memory_block
 static int memory_block_change_state(struct memory_block *mem,
 		unsigned long to_state, unsigned long from_state_req)
 {
-	int ret = 0;
+	int i, ret = 0;
 	mutex_lock(&mem->state_mutex);
 
 	if (mem->state != from_state_req) {

@@ -256,8 +258,21 @@ static int memory_block_change_state(str
 		goto out;
 	}
 
-	ret = memory_block_action(mem, to_state);
-	if (!ret)
+	if (to_state == MEM_OFFLINE)
+		mem->state = MEM_GOING_OFFLINE;
+
+	for (i = mem->start_phys_index; i <= mem->end_phys_index; i++) {
+		ret = memory_section_action(i, to_state);
+		if (ret)
+			break;
+	}
+
+	if (ret) {
+		for (i = mem->start_phys_index; i <= mem->end_phys_index; i++)
+			memory_section_action(i, from_state_req);
+
+		mem->state = from_state_req;
+	} else
 		mem->state = to_state;
 
 out:

@@ -270,20 +285,15 @@ store_mem_state(struct sys_device *dev,
 		struct sysdev_attribute *attr, const char *buf, size_t count)
 {
 	struct memory_block *mem;
-	unsigned int phys_section_nr;
 	int ret = -EINVAL;
 
 	mem = container_of(dev, struct memory_block, sysdev);
-	phys_section_nr = mem->start_phys_index;
-
-	if (!present_section_nr(phys_section_nr))
-		goto out;
 
 	if (!strncmp(buf, "online", min((int)count, 6)))
 		ret = memory_block_change_state(mem, MEM_ONLINE, MEM_OFFLINE);
 	else if(!strncmp(buf, "offline", min((int)count, 7)))
 		ret = memory_block_change_state(mem, MEM_OFFLINE, MEM_ONLINE);
-out:
+
 	if (ret)
 		return ret;
 	return count;

@@ -460,12 +470,13 @@ struct memory_block *find_memory_block(s
 	struct sys_device *sysdev;
 	struct memory_block *mem;
 	char name[sizeof(MEMORY_CLASS_NAME) + 9 + 1];
+	int block_id = base_memory_block_id(__section_nr(section));
 
 	/*
 	 * This only works because we know that section == sysdev->id
 	 * slightly redundant with sysdev_register()
 	 */
-	sprintf(&name[0], "%s%d", MEMORY_CLASS_NAME, __section_nr(section));
+	sprintf(&name[0], "%s%d", MEMORY_CLASS_NAME, block_id);
 
 	kobj = kset_find_obj(&memory_sysdev_class.kset, name);
 	if (!kobj)

@@ -477,26 +488,26 @@ struct memory_block *find_memory_block(s
 	return mem;
 }
 
-static int add_memory_block(int nid, struct mem_section *section,
-			unsigned long state, enum mem_add_context context)
+static int init_memory_block(struct memory_block **memory,
+			     struct mem_section *section, unsigned long state)
 {
-	struct memory_block *mem = kzalloc(sizeof(*mem), GFP_KERNEL);
+	struct memory_block *mem;
 	unsigned long start_pfn;
 	int ret = 0;
 
+	mem = kzalloc(sizeof(*mem), GFP_KERNEL);
 	if (!mem)
 		return -ENOMEM;
 
-	mutex_lock(&mem_sysfs_mutex);
-
-	mem->start_phys_index = __section_nr(section);
+	mem->start_phys_index = base_memory_block_id(__section_nr(section));
+	mem->end_phys_index = mem->start_phys_index + sections_per_block - 1;
 	mem->state = state;
 	atomic_inc(&mem->section_count);
 	mutex_init(&mem->state_mutex);
 	start_pfn = section_nr_to_pfn(mem->start_phys_index);
 	mem->phys_device = arch_get_memory_phys_device(start_pfn);
 
-	ret = register_memory(mem, section);
+	ret = register_memory(mem);
 	if (!ret)
 		ret = mem_create_simple_file(mem, phys_index);
 	if (!ret)

@@ -507,8 +518,29 @@ static int add_memory_block(int nid, str
 		ret = mem_create_simple_file(mem, phys_device);
 	if (!ret)
 		ret = mem_create_simple_file(mem, removable);
+
+	*memory = mem;
+	return ret;
+}
+
+static int add_memory_section(int nid, struct mem_section *section,
+			unsigned long state, enum mem_add_context context)
+{
+	struct memory_block *mem;
+	int ret = 0;
+
+	mutex_lock(&mem_sysfs_mutex);
+
+	mem = find_memory_block(section);
+	if (mem) {
+		atomic_inc(&mem->section_count);
+		kobject_put(&mem->sysdev.kobj);
+	} else
+		ret = init_memory_block(&mem, section, state);
+
 	if (!ret) {
-		if (context == HOTPLUG)
+		if (context == HOTPLUG &&
+		    atomic_read(&mem->section_count) == sections_per_block)
 			ret = register_mem_sect_under_node(mem, nid);
 	}

@@ -531,8 +563,10 @@ int remove_memory_block(unsigned long no
 		mem_remove_simple_file(mem, state);
 		mem_remove_simple_file(mem, phys_device);
 		mem_remove_simple_file(mem, removable);
-		unregister_memory(mem, section);
-	}
+		unregister_memory(mem);
+		kfree(mem);
+	} else
+		kobject_put(&mem->sysdev.kobj);
 
 	mutex_unlock(&mem_sysfs_mutex);
 	return 0;

@@ -544,7 +578,7 @@ int remove_memory_block(unsigned long no
  */
 int register_new_memory(int nid, struct mem_section *section)
 {
-	return add_memory_block(nid, section, MEM_OFFLINE, HOTPLUG);
+	return add_memory_section(nid, section, MEM_OFFLINE, HOTPLUG);
 }
 
 int unregister_memory_section(struct mem_section *section)

@@ -555,6 +589,26 @@ int unregister_memory_section(struct mem
 	return remove_memory_block(0, section, 0);
 }
 
+u32 __weak memory_block_size_bytes(void)
+{
+	return MIN_MEMORY_BLOCK_SIZE;
+}
+
+static u32 get_memory_block_size(void)
+{
+	u32 block_sz;
+
+	block_sz = memory_block_size_bytes();
+
+	/* Validate blk_sz is a power of 2 and not less than section size */
+	if ((block_sz & (block_sz - 1)) || (block_sz < MIN_MEMORY_BLOCK_SIZE)) {
+		WARN_ON(1);
+		block_sz = MIN_MEMORY_BLOCK_SIZE;
+	}
+
+	return block_sz;
+}
+
 /*
  * Initialize the sysfs support for memory devices...
  */

@@ -563,12 +617,16 @@ int __init memory_dev_init(void)
 	unsigned int i;
 	int ret;
 	int err;
+	int block_sz;
 
 	memory_sysdev_class.kset.uevent_ops = &memory_uevent_ops;
 	ret = sysdev_class_register(&memory_sysdev_class);
 	if (ret)
 		goto out;
 
+	block_sz = get_memory_block_size();
+	sections_per_block = block_sz / MIN_MEMORY_BLOCK_SIZE;
+
 	/*
 	 * Create entries for memory sections that were found
 	 * during boot and have been initialized

@@ -576,8 +634,8 @@ int __init memory_dev_init(void)
 	for (i = 0; i < NR_MEM_SECTIONS; i++) {
 		if (!present_section_nr(i))
 			continue;
-		err = add_memory_block(0, __nr_to_section(i), MEM_ONLINE,
-				       BOOT);
+		err = add_memory_section(0, __nr_to_section(i), MEM_ONLINE,
+					 BOOT);
 		if (!ret)
 			ret = err;
 	}

Nathan Fontenot

author

2010-08-09 18:41 UTC #6 lore raw

PATCH 6/8 v5 Update the node sysfs code

In reply to Nathan Fontenot

Update the node sysfs code to be aware of the new capability for a memory block to contain multiple memory sections. This requires an additional parameter to unregister_mem_sect_under_nodes so that we know which memory section of the memory block to unregister.

Signed-off-by Nathan Fontenot <[email protected]>

---
 drivers/base/memory.c |    2 +-
 drivers/base/node.c   |   12 ++++++++----
 include/linux/node.h  |    6 ++++--
 3 files changed, 13 insertions(+), 7 deletions(-)

drivers/base/node.c +8 -4

Index: linux-2.6/drivers/base/node.c
===================================================================
@@ -346,8 +346,10 @@ int register_mem_sect_under_node(struct
 		return -EFAULT;
 	if (!node_online(nid))
 		return 0;
-	sect_start_pfn = section_nr_to_pfn(mem_blk->phys_index);
-	sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1;
+
+	sect_start_pfn = section_nr_to_pfn(mem_blk->start_phys_index);
+	sect_end_pfn = section_nr_to_pfn(mem_blk->end_phys_index);
+	sect_end_pfn += PAGES_PER_SECTION - 1;
 	for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
 		int page_nid;

@@ -371,7 +373,8 @@ int register_mem_sect_under_node(struct
 }
 
 /* unregister memory section under all nodes that it spans */
-int unregister_mem_sect_under_nodes(struct memory_block *mem_blk)
+int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
+				    unsigned long phys_index)
 {
 	NODEMASK_ALLOC(nodemask_t, unlinked_nodes, GFP_KERNEL);
 	unsigned long pfn, sect_start_pfn, sect_end_pfn;

@@ -383,7 +386,8 @@ int unregister_mem_sect_under_nodes(stru
 	if (!unlinked_nodes)
 		return -ENOMEM;
 	nodes_clear(*unlinked_nodes);
-	sect_start_pfn = section_nr_to_pfn(mem_blk->phys_index);
+
+	sect_start_pfn = section_nr_to_pfn(phys_index);
 	sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1;
 	for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
 		int nid;

drivers/base/memory.c +1 -1

Index: linux-2.6/drivers/base/memory.c
===================================================================
@@ -555,9 +555,9 @@ int remove_memory_block(unsigned long no
 
 	mutex_lock(&mem_sysfs_mutex);
 	mem = find_memory_block(section);
+	unregister_mem_sect_under_nodes(mem, __section_nr(section));
 
 	if (atomic_dec_and_test(&mem->section_count)) {
-		unregister_mem_sect_under_nodes(mem);
 		mem_remove_simple_file(mem, phys_index);
 		mem_remove_simple_file(mem, end_phys_index);
 		mem_remove_simple_file(mem, state);

include/linux/node.h +4 -2

Index: linux-2.6/include/linux/node.h
===================================================================
@@ -44,7 +44,8 @@ extern int register_cpu_under_node(unsig
 extern int unregister_cpu_under_node(unsigned int cpu, unsigned int nid);
 extern int register_mem_sect_under_node(struct memory_block *mem_blk,
 						int nid);
-extern int unregister_mem_sect_under_nodes(struct memory_block *mem_blk);
+extern int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
+					   unsigned long phys_index);
 
 #ifdef CONFIG_HUGETLBFS
 extern void register_hugetlbfs_with_node(node_registration_func_t doregister,

@@ -72,7 +73,8 @@ static inline int register_mem_sect_unde
 {
 	return 0;
 }
-static inline int unregister_mem_sect_under_nodes(struct memory_block *mem_blk)
+static inline int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
+						  unsigned long phys_index)
 {
 	return 0;
 }

Nathan Fontenot

author

2010-08-09 18:42 UTC #7 lore raw

PATCH 7/8 v5 Define memory_block_size_bytes() for ppc/pseries

In reply to Nathan Fontenot

Define a version of memory_block_size_bytes() for powerpc/pseries such that a memory block spans an entire lmb.

Signed-off-by Nathan Fontenot <[email protected]>

---
 arch/powerpc/platforms/pseries/hotplug-memory.c |   66 +++++++++++++++++++-----
 1 file changed, 53 insertions(+), 13 deletions(-)

arch/powerpc/platforms/pseries/hotplug-memory.c +53 ~~-13~~

Index: linux-2.6/arch/powerpc/platforms/pseries/hotplug-memory.c
===================================================================
@@ -17,6 +17,54 @@
 #include <asm/pSeries_reconfig.h>
 #include <asm/sparsemem.h>
 
+static u32 get_memblock_size(void)
+{
+	struct device_node *np;
+	unsigned int memblock_size = 0;
+
+	np = of_find_node_by_path("/ibm,dynamic-reconfiguration-memory");
+	if (np) {
+		const unsigned long *size;
+
+		size = of_get_property(np, "ibm,lmb-size", NULL);
+		memblock_size = size ? *size : 0;
+
+		of_node_put(np);
+	} else {
+		unsigned int memzero_size = 0;
+		const unsigned int *regs;
+
+		np = of_find_node_by_path("/memory@0");
+		if (np) {
+			regs = of_get_property(np, "reg", NULL);
+			memzero_size = regs ? regs[3] : 0;
+			of_node_put(np);
+		}
+
+		if (memzero_size) {
+			/* We now know the size of memory@0, use this to find
+			 * the first memoryblock and get its size.
+			 */
+			char buf[64];
+
+			sprintf(buf, "/memory@%x", memzero_size);
+			np = of_find_node_by_path(buf);
+			if (np) {
+				regs = of_get_property(np, "reg", NULL);
+				memblock_size = regs ? regs[3] : 0;
+				of_node_put(np);
+			}
+		}
+	}
+
+	return memblock_size;
+}
+
+u32 memory_block_size_bytes(void)
+{
+	return get_memblock_size();
+}
+
 static int pseries_remove_memblock(unsigned long base, unsigned int memblock_size)
 {
 	unsigned long start, start_pfn;

@@ -127,30 +175,22 @@ static int pseries_add_memory(struct dev
 
 static int pseries_drconf_memory(unsigned long *base, unsigned int action)
 {
-	struct device_node *np;
-	const unsigned long *lmb_size;
+	unsigned long memblock_size;
 	int rc;
 
-	np = of_find_node_by_path("/ibm,dynamic-reconfiguration-memory");
-	if (!np)
+	memblock_size = get_memblock_size();
+	if (!memblock_size)
 		return -EINVAL;
 
-	lmb_size = of_get_property(np, "ibm,lmb-size", NULL);
-	if (!lmb_size) {
-		of_node_put(np);
-		return -EINVAL;
-	}
-
 	if (action == PSERIES_DRCONF_MEM_ADD) {
-		rc = memblock_add(*base, *lmb_size);
+		rc = memblock_add(*base, memblock_size);
 		rc = (rc < 0) ? -EINVAL : 0;
 	} else if (action == PSERIES_DRCONF_MEM_REMOVE) {
-		rc = pseries_remove_memblock(*base, *lmb_size);
+		rc = pseries_remove_memblock(*base, memblock_size);
 	} else {
 		rc = -EINVAL;
 	}
 
-	of_node_put(np);
 	return rc;
 }

Nathan Fontenot

author

2010-08-09 18:44 UTC #8 lore raw

PATCH 8/8 v5 Update memory-hotplug documentation

In reply to Nathan Fontenot

Update the memory hotplug documentation to reflect the new behaviors of memory blocks reflected in sysfs.

Signed-off-by Nathan Fontent <[email protected]>

---
 Documentation/memory-hotplug.txt |   46 +++++++++++++++++++++++++--------------
 1 file changed, 30 insertions(+), 16 deletions(-)

Documentation/memory-hotplug.txt +30 ~~-16~~

Index: linux-2.6/Documentation/memory-hotplug.txt
===================================================================
@@ -126,36 +126,50 @@ config options.
 --------------------------------
 4 sysfs files for memory hotplug
 --------------------------------
-All sections have their device information under /sys/devices/system/memory as
+All sections have their device information in sysfs.  Each section is part of
+a memory block under /sys/devices/system/memory as
 
 /sys/devices/system/memory/memoryXXX
-(XXX is section id.)
+(XXX is the section id.)
 
-Now, XXX is defined as start_address_of_section / section_size.
+Now, XXX is defined as (start_address_of_section / section_size) of the first
+section contained in the memory block.  The files 'phys_index' and
+'end_phys_index' under each directory report the beginning and end section id's
+for the memory block covered by the sysfs directory.  It is expected that all
+memory sections in this range are present and no memory holes exist in the
+range. Currently there is no way to determine if there is a memory hole, but
+the existence of one should not affect the hotplug capabilities of the memory
+block.
 
 For example, assume 1GiB section size. A device for a memory starting at
 0x100000000 is /sys/device/system/memory/memory4
 (0x100000000 / 1Gib = 4)
 This device covers address range [0x100000000 ... 0x140000000)
 
-Under each section, you can see 4 files.
+Under each section, you can see 5 files.
 
-/sys/devices/system/memory/memoryXXX/phys_index
+/sys/devices/system/memory/memoryXXX/start_phys_index
+/sys/devices/system/memory/memoryXXX/end_phys_index
 /sys/devices/system/memory/memoryXXX/phys_device
 /sys/devices/system/memory/memoryXXX/state
 /sys/devices/system/memory/memoryXXX/removable
 
-'phys_index' : read-only and contains section id, same as XXX.
-'state'      : read-write
-               at read:  contains online/offline state of memory.
-               at write: user can specify "online", "offline" command
-'phys_device': read-only: designed to show the name of physical memory device.
-               This is not well implemented now.
-'removable'  : read-only: contains an integer value indicating
-               whether the memory section is removable or not
-               removable.  A value of 1 indicates that the memory
-               section is removable and a value of 0 indicates that
-               it is not removable.
+'phys_index'      : read-only and contains section id of the first section
+		    in the memory block, same as XXX.
+'end_phys_index'  : read-only and contains section id of the last section
+		    in the memory block.
+'state'           : read-write
+                    at read:  contains online/offline state of memory.
+                    at write: user can specify "online", "offline" command
+                    which will be performed on al sections in the block.
+'phys_device'     : read-only: designed to show the name of physical memory
+                    device.  This is not well implemented now.
+'removable'       : read-only: contains an integer value indicating
+                    whether the memory block is removable or not
+                    removable.  A value of 1 indicates that the memory
+                    block is removable and a value of 0 indicates that
+                    it is not removable. A memory block is removable only if
+                    every section in the block is removable.
 
 NOTE:
   These directories/files appear after physical memory hotplug phase.

Nishanth Aravamudan

2010-08-09 20:45 UTC #9 lore raw

Re: [PATCH 8/8] v5 Update memory-hotplug documentation

Quoted 2 lines · Nathan Fontenot

Update the memory hotplug documentation to reflect the new behaviors of memory blocks reflected in sysfs.

<snip>

Quoted 4 lines

Index: linux-2.6/Documentation/memory-hotplug.txt
===================================================================
Documentation/memory-hotplug.txt +0 -0

<snip>

Quoted 8 lines

Documentation/memory-hotplug.txt +2 -2

-/sys/devices/system/memory/memoryXXX/phys_index
+/sys/devices/system/memory/memoryXXX/start_phys_index
+/sys/devices/system/memory/memoryXXX/end_phys_index
 /sys/devices/system/memory/memoryXXX/phys_device
 /sys/devices/system/memory/memoryXXX/state
 /sys/devices/system/memory/memoryXXX/removable
 
-'phys_index' : read-only and contains section id, same as XXX.

<snip>

Quoted 1 line

+'phys_index' : read-only and contains section id of the first section

Shouldn't this be "start_phys_index"?

Thanks,
Nish

Signature · 2 lines

Nishanth Aravamudan <[email protected]>
Linux Technology Center

Nishanth Aravamudan

2010-08-09 20:48 UTC #10 lore raw

Re: [PATCH 8/8] v5 Update memory-hotplug documentation

Quoted 20 lines · Nishanth Aravamudan

Quoted 2 lines · Nathan Fontenot
Update the memory hotplug documentation to reflect the new behaviors of memory blocks reflected in sysfs.
<snip>
Quoted 4 lines
Index: linux-2.6/Documentation/memory-hotplug.txt
===================================================================
Documentation/memory-hotplug.txt +0 -0
<snip>
Quoted 7 lines
Documentation/memory-hotplug.txt +2 -1
-/sys/devices/system/memory/memoryXXX/phys_index
+/sys/devices/system/memory/memoryXXX/start_phys_index
+/sys/devices/system/memory/memoryXXX/end_phys_index
 /sys/devices/system/memory/memoryXXX/phys_device
 /sys/devices/system/memory/memoryXXX/state
 /sys/devices/system/memory/memoryXXX/removable

Quoted 7 lines

Quoted 1 line
-'phys_index' : read-only and contains section id, same as XXX.
<snip>
Quoted 1 line
+'phys_index' : read-only and contains section id of the first section
Shouldn't this be "start_phys_index"?

Ah, actually it's that the Documentation change doesn't seem to agree with patch 2/8 ? That is, 2/8 leaves phys_index in place, but changes several variables, while this patch indicates its removal?

Thanks,
Nish

Signature · 8 lines

Nishanth Aravamudan <[email protected]>
Linux Technology Center

--
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the body to [email protected].  For more info on Linux MM,
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Nathan Fontenot

author

2010-08-10 12:17 UTC #11 lore raw

Re: [PATCH 8/8] v5 Update memory-hotplug documentation

In reply to Nishanth Aravamudan

Quoted 20 lines · Nishanth Aravamudan

Quoted 2 lines · Nathan Fontenot
Update the memory hotplug documentation to reflect the new behaviors of memory blocks reflected in sysfs.
<snip>
Quoted 4 lines
Index: linux-2.6/Documentation/memory-hotplug.txt
===================================================================
Documentation/memory-hotplug.txt +0 -0
<snip>
Quoted 7 lines
Documentation/memory-hotplug.txt +2 -1
-/sys/devices/system/memory/memoryXXX/phys_index
+/sys/devices/system/memory/memoryXXX/start_phys_index
+/sys/devices/system/memory/memoryXXX/end_phys_index
 /sys/devices/system/memory/memoryXXX/phys_device
 /sys/devices/system/memory/memoryXXX/state
 /sys/devices/system/memory/memoryXXX/removable

Quoted 7 lines

Quoted 1 line
-'phys_index' : read-only and contains section id, same as XXX.
<snip>
Quoted 1 line
+'phys_index' : read-only and contains section id of the first section
Shouldn't this be "start_phys_index"?

Hmmm... looks like I missed something in the documentation.

The property should be 'phys_index'. I thought about changing it to 'start_phys_index' but that was rejected. The listing of the files above is wrong in this patch, it should be

+/sys/devices/system/memory/memoryXXX/phys_index +/sys/devices/system/memory/memoryXXX/end_phys_index

Thanks,

Nathan

Dave Hansen

Acked-by on the v1 series

2010-08-11 15:19 UTC #12 lore raw

In reply to Nathan Fontenot

Quoted 8 lines · Nathan Fontenot

This set of patches de-couples the idea that there is a single directory in sysfs for each memory section. The intent of the patches is to reduce the number of sysfs directories created to resolve a boot-time performance issue. On very large systems boot time are getting very long (as seen on powerpc hardware) due to the enormous number of sysfs directories being created. On a system with 1 TB of memory we create ~63,000 directories. For even larger systems boot times are being measured in hours.

Hi Nathan,

The set is looking pretty good to me. We _might_ want to up the ante in the future and allow it to be even more dynamic than this, but this looks like a good start to me.

BTW, have you taken a look at what the hotplug events look like if only a single section (not filling up a whole block) is added?

Feel free to add my:

Acked-by Dave Hansen <[email protected]>

-- Dave

Andrew Morton

maintainer

2010-08-12 19:08 UTC #13 lore raw

In reply to Nathan Fontenot

Quoted 8 lines · On Mon, 09 Aug 2010 12:53:00 -0500 Nathan Fontenot <[email protected]> wrote:

This set of patches de-couples the idea that there is a single directory in sysfs for each memory section. The intent of the patches is to reduce the number of sysfs directories created to resolve a boot-time performance issue. On very large systems boot time are getting very long (as seen on powerpc hardware) due to the enormous number of sysfs directories being created. On a system with 1 TB of memory we create ~63,000 directories. For even larger systems boot times are being measured in hours.

And those "hours" are mainly due to this problem, I assume.

Quoted 7 lines

This set of patches allows for each directory created in sysfs to cover more than one memory section. The default behavior for sysfs directory creation is the same, in that each directory represents a single memory section. A new file 'end_phys_index' in each directory contains the physical_id of the last memory section covered by the directory so that users can easily determine the memory section range of a directory.

What you're proposing appears to be a non-back-compatible userspace-visible change. This is a big issue!

It's not an unresolvable issue, as this is a must-fix problem. But you should tell us what your proposal is to prevent breakage of existing installations. A Kconfig option would be good, but a boot-time kernel command line option which selects the new format would be much better.

However you didn't mention this issue at all, and it's the most important one.

Quoted 7 lines

Updates for version 5 of the patchset include the following:
Patch 4/8 Add mutex for add/remove of memory blocks
- Define the mutex using DEFINE_MUTEX macro.
Patch 8/8 Update memory-hotplug documentation
- Add information concerning memory holes in phys_index..end_phys_index.

And you forgot to tell us how long those machines boot with the patchset applied, which is the entire point of the patchset!

Dave Hansen

2010-08-12 20:07 UTC #14 lore raw

Quoted 10 lines · Andrew Morton

Quoted 7 lines
This set of patches allows for each directory created in sysfs to cover more than one memory section. The default behavior for sysfs directory creation is the same, in that each directory represents a single memory section. A new file 'end_phys_index' in each directory contains the physical_id of the last memory section covered by the directory so that users can easily determine the memory section range of a directory.
What you're proposing appears to be a non-back-compatible userspace-visible change. This is a big issue!

Nathan, one thought to get around this at the moment would be to bump up the size that we export in /sys/devices/system/memory/block_size_bytes. I think you have already done most of the hard work to accomplish this.

You can still add the end_phys_index stuff. But, for now, it would always be equal to start_phys_index.

-- Dave

Nathan Fontenot

author

2010-08-16 14:34 UTC #15 lore raw

In reply to Andrew Morton

Quoted 12 lines · Andrew Morton

Quoted 8 lines · On Mon, 09 Aug 2010 12:53:00 -0500 Nathan Fontenot <[email protected]> wrote:
This set of patches de-couples the idea that there is a single directory in sysfs for each memory section. The intent of the patches is to reduce the number of sysfs directories created to resolve a boot-time performance issue. On very large systems boot time are getting very long (as seen on powerpc hardware) due to the enormous number of sysfs directories being created. On a system with 1 TB of memory we create ~63,000 directories. For even larger systems boot times are being measured in hours.

Quoted 1 line

And those "hours" are mainly due to this problem, I assume.

Yes, those hours are spent creating the sysfs directories for each of the memory sections.

Quoted 9 lines

Quoted 8 lines
This set of patches allows for each directory created in sysfs to cover more than one memory section. The default behavior for sysfs directory creation is the same, in that each directory represents a single memory section. A new file 'end_phys_index' in each directory contains the physical_id of the last memory section covered by the directory so that users can easily determine the memory section range of a directory.

Quoted 7 lines

What you're proposing appears to be a non-back-compatible userspace-visible change. This is a big issue!
It's not an unresolvable issue, as this is a must-fix problem. But you should tell us what your proposal is to prevent breakage of existing installations. A Kconfig option would be good, but a boot-time kernel command line option which selects the new format would be much better.

This shouldn't break existing installations, unless an architecture chooses to do so. With my patch only the powerpc/pseries arch is updated such that what is seen in userspace is different.

The default behavior is maintained for all architectures unless they define their own version of memory_block_size_bytes(). The default definition of this routine (defined as __weak in Patch 5/8) sets the memory block size to the same size it currently is, and thus preserving the exisitng 1 sysfs directory per memory section. The only change that will be seen is a new propery for memory section, end_phys_addr, which will have the same value as the existing 'phys_addr' property.

Quoted 7 lines

However you didn't mention this issue at all, and it's the most important one.
Quoted 2 lines
Updates for version 5 of the patchset include the following:

Quoted 8 lines

Quoted 5 lines
Patch 4/8 Add mutex for add/remove of memory blocks
- Define the mutex using DEFINE_MUTEX macro.
Patch 8/8 Update memory-hotplug documentation
- Add information concerning memory holes in phys_index..end_phys_index.
And you forgot to tell us how long those machines boot with the patchset applied, which is the entire point of the patchset!

Yes, I am working on getting more time on our large systems to get performance numbers with this patch. I'll post them when I get them.

-Nathan

Dave Hansen

2010-08-31 18:12 UTC #16 lore raw

Quoted 8 lines · Nathan Fontenot

Quoted 4 lines
It's not an unresolvable issue, as this is a must-fix problem. But you should tell us what your proposal is to prevent breakage of existing installations. A Kconfig option would be good, but a boot-time kernel command line option which selects the new format would be much better.
This shouldn't break existing installations, unless an architecture chooses to do so. With my patch only the powerpc/pseries arch is updated such that what is seen in userspace is different.

Even if an arch defines the override for the sysfs dir size, I still don't think this breaks anything (it shouldn't). We move _all_ of the directories over, all at once, to a single, uniform size. The only apparent change to a user moving kernels would be a larger block_size_bytes (which is certainly not changing the ABI) and a new sysfs file for the end of the section. The new sysfs file is _completely_ redundant at this point.

The architecture is only supposed to bump up the directory size when it *KNOWS* that all operations will be done at the larger section size, such as if the specific hardware has physical DIMMs which are much larger than SECTION_SIZE.

Let's say we have a system with 20MB of memory, SECTION_SIZE of 1MB and a sysfs dir size of 4MB.

Before the patch, we have 20 directories: one for each section. After this patch, we have 5 directories.

The thing that I think is the next step, but that we _will_ probably need eventually is this, take the 5 sysfs dirs in the above case:

	0->3, 4->7, 8->11, 12->15, 16->19

and turn that into a single one:

	0->19

*That* will require changing the ABI, but we could certainly have some bloated and slow, but backward-compatible mode.

-- Dave

Anton Blanchard

Tested-by on the v1 series

2010-08-31 21:57 UTC #17 lore raw

In reply to Nathan Fontenot

Hi Nathan,

Quoted 9 lines

This set of patches de-couples the idea that there is a single directory in sysfs for each memory section. The intent of the patches is to reduce the number of sysfs directories created to resolve a boot-time performance issue. On very large systems boot time are getting very long (as seen on powerpc hardware) due to the enormous number of sysfs directories being created. On a system with 1 TB of memory we create ~63,000 directories. For even larger systems boot times are being measured in hours.

Quoted 7 lines

This set of patches allows for each directory created in sysfs to cover more than one memory section. The default behavior for sysfs directory creation is the same, in that each directory represents a single memory section. A new file 'end_phys_index' in each directory contains the physical_id of the last memory section covered by the directory so that users can easily determine the memory section range of a directory.

I tested this on a POWER7 with 2TB memory and the boot time improved from greater than 6 hours (I gave up), to under 5 minutes. Nice!

Tested-by Anton Blanchard <[email protected]>

Anton

Nathan Fontenot

author

2010-09-02 17:39 UTC #18 lore raw

Quoted 20 lines · Anton Blanchard

Hi Nathan,
Quoted 9 lines
This set of patches de-couples the idea that there is a single directory in sysfs for each memory section. The intent of the patches is to reduce the number of sysfs directories created to resolve a boot-time performance issue. On very large systems boot time are getting very long (as seen on powerpc hardware) due to the enormous number of sysfs directories being created. On a system with 1 TB of memory we create ~63,000 directories. For even larger systems boot times are being measured in hours.
Quoted 7 lines
This set of patches allows for each directory created in sysfs to cover more than one memory section. The default behavior for sysfs directory creation is the same, in that each directory represents a single memory section. A new file 'end_phys_index' in each directory contains the physical_id of the last memory section covered by the directory so that users can easily determine the memory section range of a directory.

Quoted 2 lines

I tested this on a POWER7 with 2TB memory and the boot time improved from greater than 6 hours (I gave up), to under 5 minutes. Nice!

Thanks for testing this out. I was able to test this on a 1 TB system and saw memory sysfs creation times go from 10 minutes to a few seconds. It's good to see the difference for a 2 TB system.

-Nathan