Re: [PATCH RFCv2 1/4] mm/memory_hotplug: Introduce memory block types

Wei Yang
2018-12-01T01:25:07Z

On Fri, Nov 30, 2018 at 06:59:19PM +0100, David Hildenbrand wrote:
>Memory onlining should always be handled by user space, because only user
>space knows which use cases it wants to satisfy. E.g. memory might be
>onlined to the MOVABLE zone even if it can never be removed from the
>system, e.g. to make usage of huge pages more reliable.
>
>However to implement such rules (especially default rules in distributions)
>we need more information about the memory that was added in user space.
>
>E.g. on x86 we want to online memory provided by balloon devices (e.g.
>XEN, Hyper-V) differently (-> will not be unplugged by offlining the whole
>block) than ordinary DIMMs (-> might eventually be unplugged by offlining
>the whole block). This might also become relevat for other architectures.
>
>Also, udev rules right now check if running on s390x and treat all added
>memory blocks as standby memory (-> don't online automatically). As soon as
>we support other memory hotplug mechanism (e.g. virtio-mem) checks would
>have to get more involved (e.g. also check if under KVM) but eventually
>also wrong (e.g. if KVM ever supports standby memory we are doomed).
>
>I decided to allow to specify the type of memory that is getting added
>to the system. Let's start with two types, BOOT and UNSPECIFIED to get the
>basic infrastructure running. We'll introduce and use further types in
>follow-up patches. For now we classify any hotplugged memory temporarily
>as as UNSPECIFIED (which will eventually be dropped later on).
>
>Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>Cc: "Rafael J. Wysocki" <rafael@kernel.org>
>Cc: Andrew Morton <akpm@linux-foundation.org>
>Cc: Ingo Molnar <mingo@kernel.org>
>Cc: Pavel Tatashin <pasha.tatashin@oracle.com>
>Cc: Stephen Rothwell <sfr@canb.auug.org.au>
>Cc: Andrew Banman <andrew.banman@hpe.com>
>Cc: "mike.travis@hpe.com" <mike.travis@hpe.com>
>Cc: Oscar Salvador <osalvador@suse.com>
>Cc: Dave Hansen <dave.hansen@linux.intel.com>
>Cc: Michal Hocko <mhocko@kernel.org>
>Cc: Michal Such??nek <msuchanek@suse.de>
>Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
>Cc: Dan Williams <dan.j.williams@intel.com>
>Cc: Pavel Tatashin <pavel.tatashin@microsoft.com>
>Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
>Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
>Signed-off-by: David Hildenbrand <david@redhat.com>
>---
> drivers/base/memory.c | 38 +++++++++++++++++++++++++++++++++++---
> include/linux/memory.h | 27 +++++++++++++++++++++++++++
> 2 files changed, 62 insertions(+), 3 deletions(-)
>
>diff --git a/drivers/base/memory.c b/drivers/base/memory.c
>index 0c290f86ab20..17f2985c07c5 100644
>--- a/drivers/base/memory.c
>+++ b/drivers/base/memory.c
>@@ -381,6 +381,29 @@ static ssize_t show_phys_device(struct device *dev,
> return sprintf(buf, "%d\n", mem->phys_device);
> }
>
>+static ssize_t type_show(struct device *dev, struct device_attribute *attr,
>+ char *buf)
>+{
>+ struct memory_block *mem = to_memory_block(dev);
>+ ssize_t len = 0;
>+
>+ switch (mem->type) {
>+ case MEMORY_BLOCK_UNSPECIFIED:
>+ len = sprintf(buf, "unspecified\n");
>+ break;
>+ case MEMORY_BLOCK_BOOT:
>+ len = sprintf(buf, "boot\n");
>+ break;
>+ default:
>+ len = sprintf(buf, "ERROR-UNKNOWN-%ld\n",
>+ mem->state);
>+ WARN_ON(1);
>+ break;
>+ }
>+
>+ return len;
>+}
>+
> #ifdef CONFIG_MEMORY_HOTREMOVE
> static void print_allowed_zone(char *buf, int nid, unsigned long start_pfn,
> unsigned long nr_pages, int online_type,
>@@ -442,6 +465,7 @@ 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_RO(type);

This is correct, while looks not consistent with other attributes.

Not that beautiful :-)

>
> /*
> * Block size attribute stuff
>@@ -620,6 +644,7 @@ static struct attribute *memory_memblk_attrs[] = {
> &dev_attr_state.attr,
> &dev_attr_phys_device.attr,
> &dev_attr_removable.attr,
>+ &dev_attr_type.attr,
> #ifdef CONFIG_MEMORY_HOTREMOVE
> &dev_attr_valid_zones.attr,
> #endif
>@@ -657,13 +682,17 @@ int register_memory(struct memory_block *memory)
> }
>
> static int init_memory_block(struct memory_block **memory,
>- struct mem_section *section, unsigned long state)
>+ struct mem_section *section, unsigned long state,
>+ int type)
> {
> struct memory_block *mem;
> unsigned long start_pfn;
> int scn_nr;
> int ret = 0;
>
>+ if (type == MEMORY_BLOCK_NONE)
>+ return -EINVAL;

No one will pass in this value. Can we omit this check for now?

>+
> mem = kzalloc(sizeof(*mem), GFP_KERNEL);
> if (!mem)
> return -ENOMEM;
>@@ -675,6 +704,7 @@ static int init_memory_block(struct memory_block **memory,
> mem->state = state;
> start_pfn = section_nr_to_pfn(mem->start_section_nr);
> mem->phys_device = arch_get_memory_phys_device(start_pfn);
>+ mem->type = type;
>
> ret = register_memory(mem);
>
>@@ -699,7 +729,8 @@ static int add_memory_block(int base_section_nr)
>
> if (section_count == 0)
> return 0;
>- ret = init_memory_block(&mem, __nr_to_section(section_nr), MEM_ONLINE);
>+ ret = init_memory_block(&mem, __nr_to_section(section_nr), MEM_ONLINE,
>+ MEMORY_BLOCK_BOOT);
> if (ret)
> return ret;
> mem->section_count = section_count;
>@@ -722,7 +753,8 @@ int hotplug_memory_register(int nid, struct mem_section *section)
> mem->section_count++;
> put_device(&mem->dev);
> } else {
>- ret = init_memory_block(&mem, section, MEM_OFFLINE);
>+ ret = init_memory_block(&mem, section, MEM_OFFLINE,
>+ MEMORY_BLOCK_UNSPECIFIED);
> if (ret)
> goto out;
> mem->section_count++;
>diff --git a/include/linux/memory.h b/include/linux/memory.h
>index d75ec88ca09d..06268e96e0da 100644
>--- a/include/linux/memory.h
>+++ b/include/linux/memory.h
>@@ -34,12 +34,39 @@ struct memory_block {
> int (*phys_callback)(struct memory_block *);
> struct device dev;
> int nid; /* NID for this memory block */
>+ int type; /* type of this memory block */
> };
>
> int arch_get_memory_phys_device(unsigned long start_pfn);
> unsigned long memory_block_size_bytes(void);
> int set_memory_block_size_order(unsigned int order);
>
>+/*
>+ * Memory block types allow user space to formulate rules if and how to
>+ * online memory blocks. The types are exposed to user space as text
>+ * strings in sysfs.
>+ *
>+ * MEMORY_BLOCK_NONE:
>+ * No memory block is to be created (e.g. device memory). Not exposed to
>+ * user space.
>+ *
>+ * MEMORY_BLOCK_UNSPECIFIED:
>+ * The type of memory block was not further specified when adding the
>+ * memory block.
>+ *
>+ * MEMORY_BLOCK_BOOT:
>+ * This memory block was added during boot by the basic system. No
>+ * specific device driver takes care of this memory block. This memory
>+ * block type is onlined automatically by the kernel during boot and might
>+ * later be managed by a different device driver, in which case the type
>+ * might change.
>+ */
>+enum {
>+ MEMORY_BLOCK_NONE = 0,
>+ MEMORY_BLOCK_UNSPECIFIED,
>+ MEMORY_BLOCK_BOOT,
>+};
>+
> /* These states are exposed to userspace as text strings in sysfs */
> #define MEM_ONLINE (1<<0) /* exposed to userspace */
> #define MEM_GOING_OFFLINE (1<<1) /* exposed to userspace */
>--
>2.17.2

--
Wei Yang
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