Re: [PATCH v2] memory-hotplug: add sysfs zones_online_to attribute

[Yasuaki Ishimatsu]

(2014/08/13 13:10), Zhang Zhen wrote:
> Currently memory-hotplug has two limits:
> 1. If the memory block is in ZONE_NORMAL, you can change it to
> ZONE_MOVABLE, but this memory block must be adjacent to ZONE_MOVABLE.
> 2. If the memory block is in ZONE_MOVABLE, you can change it to
> ZONE_NORMAL, but this memory block must be adjacent to ZONE_NORMAL.
>
> With this patch, we can easy to know a memory block can be onlined to
> which zone, and don't need to know the above two limits.
>
> Updated the related Documentation.
>
> Change v1 -> v2:
> - optimize the implementation following Dave Hansen's suggestion
>
> Signed-off-by: Zhang Zhen <zhenzhang.zhang@xxxxxxxxxx>
> ---
>   Documentation/ABI/testing/sysfs-devices-memory |  8 ++++
>   Documentation/memory-hotplug.txt               |  4 +-
>   drivers/base/memory.c                          | 62 ++++++++++++++++++++++++++
>   include/linux/memory_hotplug.h                 |  1 +
>   mm/memory_hotplug.c                            |  2 +-
>   5 files changed, 75 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-devices-memory b/Documentation/ABI/testing/sysfs-devices-memory
> index 7405de2..2b2a1d7 100644
> --- a/Documentation/ABI/testing/sysfs-devices-memory
> +++ b/Documentation/ABI/testing/sysfs-devices-memory
> @@ -61,6 +61,14 @@ Users:		hotplug memory remove tools
>   		http://www.ibm.com/developerworks/wikis/display/LinuxP/powerpc-utils
>
>
> +What:           /sys/devices/system/memory/memoryX/zones_online_to
> +Date:           July 2014
> +Contact:	Zhang Zhen <zhenzhang.zhang@xxxxxxxxxx>
> +Description:
> +		The file /sys/devices/system/memory/memoryX/zones_online_to
> +		is read-only and is designed to show which zone this memory block can
> +		be onlined to.
> +
>   What:		/sys/devices/system/memoryX/nodeY
>   Date:		October 2009
>   Contact:	Linux Memory Management list <linux-mm@xxxxxxxxx>
> diff --git a/Documentation/memory-hotplug.txt b/Documentation/memory-hotplug.txt
> index 45134dc..5b34e33 100644
> --- a/Documentation/memory-hotplug.txt
> +++ b/Documentation/memory-hotplug.txt
> @@ -155,6 +155,7 @@ Under each memory block, you can see 4 files:
>   /sys/devices/system/memory/memoryXXX/phys_device
>   /sys/devices/system/memory/memoryXXX/state
>   /sys/devices/system/memory/memoryXXX/removable
> +/sys/devices/system/memory/memoryXXX/zones_online_to
>
>   'phys_index'      : read-only and contains memory block id, same as XXX.
>   'state'           : read-write
> @@ -170,6 +171,8 @@ Under each memory block, you can see 4 files:
>                       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.
> +'zones_online_to' : read-only: designed to show which zone this memory block
> +		    can be onlined to.
>
>   NOTE:
>     These directories/files appear after physical memory hotplug phase.
> @@ -408,7 +411,6 @@ node if necessary.
>     - allowing memory hot-add to ZONE_MOVABLE. maybe we need some switch like
>       sysctl or new control file.
>     - showing memory block and physical device relationship.
> -  - showing memory block is under ZONE_MOVABLE or not
>     - test and make it better memory offlining.
>     - support HugeTLB page migration and offlining.
>     - memmap removing at memory offline.
> diff --git a/drivers/base/memory.c b/drivers/base/memory.c
> index a2e13e2..b5d693f 100644
> --- a/drivers/base/memory.c
> +++ b/drivers/base/memory.c
> @@ -373,10 +373,71 @@ static ssize_t show_phys_device(struct device *dev,
>   	return sprintf(buf, "%d\n", mem->phys_device);
>   }
>
> +static int __zones_online_to(unsigned long end_pfn,
> +				struct page *first_page, unsigned long nr_pages)
> +{
> +	struct zone *zone_next;
> +

> +	/*The mem block is the last block of memory.*/
> +	if (!pfn_valid(end_pfn + 1))
> +		return 1;

The check is not enough if memory has hole as follows:

PFN       0x00          0xd0          0xe0          0xf0
            +-------------+-------------+-------------+
zone type   |   Normal    |     hole    |   Normal    |
            +-------------+-------------+-------------+

In this case, 0xd1 is invalid pfn. But __zones_online_to should return 0
since 0xe0-0xf0 is Normal zone.

Thanks,
Yasuaki Ishimatsu


> +	zone_next = page_zone(first_page + nr_pages);
> +	if (zone_idx(zone_next) == ZONE_MOVABLE)
> +		return 1;
> +	return 0;
> +}
> +
> +static ssize_t show_zones_online_to(struct device *dev,
> +				struct device_attribute *attr, char *buf)
> +{
> +	struct memory_block *mem = to_memory_block(dev);
> +	unsigned long start_pfn, end_pfn;
> +	unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block;
> +	struct page *first_page;
> +	struct zone *zone, *zone_prev;
> +
> +	start_pfn = section_nr_to_pfn(mem->start_section_nr);
> +	end_pfn = start_pfn + nr_pages;
> +	first_page = pfn_to_page(start_pfn);
> +
> +	/*The block contains more than one zone can not be offlined.*/
> +	if (!test_pages_in_a_zone(start_pfn, end_pfn))
> +		return sprintf(buf, "none\n");
> +
> +	zone = page_zone(first_page);
> +
> +#ifdef CONFIG_HIGHMEM
> +	if (zone_idx(zone) == ZONE_HIGHMEM) {
> +		if (__zones_online_to(end_pfn, first_page, nr_pages))
> +			return sprintf(buf, "%s %s\n",
> +					zone->name, (zone + 1)->name);
> +	}
> +#else
> +	if (zone_idx(zone) == ZONE_NORMAL) {
> +		if (__zones_online_to(end_pfn, first_page, nr_pages))
> +			return sprintf(buf, "%s %s\n",
> +					zone->name, (zone + 1)->name);
> +	}
> +#endif
> +
> +	if (zone_idx(zone) == ZONE_MOVABLE) {
> +		if (!pfn_valid(start_pfn - nr_pages))
> +			return sprintf(buf, "%s %s\n",
> +						zone->name, (zone - 1)->name);
> +		zone_prev = page_zone(first_page - nr_pages);
> +		if (zone_idx(zone_prev) != ZONE_MOVABLE)
> +			return sprintf(buf, "%s %s\n",
> +						zone->name, (zone - 1)->name);
> +	}
> +
> +	return sprintf(buf, "%s\n", zone->name);
> +}
> +
>   static DEVICE_ATTR(phys_index, 0444, show_mem_start_phys_index, NULL);
>   static DEVICE_ATTR(state, 0644, show_mem_state, store_mem_state);
>   static DEVICE_ATTR(phys_device, 0444, show_phys_device, NULL);
>   static DEVICE_ATTR(removable, 0444, show_mem_removable, NULL);
> +static DEVICE_ATTR(zones_online_to, 0444, show_zones_online_to, NULL);
>
>   /*
>    * Block size attribute stuff
> @@ -523,6 +584,7 @@ static struct attribute *memory_memblk_attrs[] = {
>   	&dev_attr_state.attr,
>   	&dev_attr_phys_device.attr,
>   	&dev_attr_removable.attr,
> +	&dev_attr_zones_online_to.attr,
>   	NULL
>   };
>
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index d9524c4..8f1a419 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -84,6 +84,7 @@ extern int zone_grow_waitqueues(struct zone *zone, unsigned long nr_pages);
>   extern int add_one_highpage(struct page *page, int pfn, int bad_ppro);
>   /* VM interface that may be used by firmware interface */
>   extern int online_pages(unsigned long, unsigned long, int);
> +extern int test_pages_in_a_zone(unsigned long, unsigned long);
>   extern void __offline_isolated_pages(unsigned long, unsigned long);
>
>   typedef void (*online_page_callback_t)(struct page *page);
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 2ff8c23..29d8693 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1307,7 +1307,7 @@ int is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages)
>   /*
>    * Confirm all pages in a range [start, end) is belongs to the same zone.
>    */
> -static int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
> +int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
>   {
>   	unsigned long pfn;
>   	struct zone *zone = NULL;


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