In the current kernel, memory tiers are defined implicitly via a demotion path relationship between NUMA nodes, which is created during the kernel initialization and updated when a NUMA node is hot-added or hot-removed. The current implementation puts all nodes with CPU into the top tier, and builds the tier hierarchy tier-by-tier by establishing the per-node demotion targets based on the distances between nodes. This current memory tier kernel interface needs to be improved for several important use cases, The current tier initialization code always initializes each memory-only NUMA node into a lower tier. But a memory-only NUMA node may have a high performance memory device (e.g. a DRAM device attached via CXL.mem or a DRAM-backed memory-only node on a virtual machine) and should be put into a higher tier. The current tier hierarchy always puts CPU nodes into the top tier. But on a system with HBM or GPU devices, the memory-only NUMA nodes mapping these devices should be in the top tier, and DRAM nodes with CPUs are better to be placed into the next lower tier. With current kernel higher tier node can only be demoted to selected nodes on the next lower tier as defined by the demotion path, not any other node from any lower tier. This strict, hard-coded demotion order does not work in all use cases (e.g. some use cases may want to allow cross-socket demotion to another node in the same demotion tier as a fallback when the preferred demotion node is out of space), This demotion order is also inconsistent with the page allocation fallback order when all the nodes in a higher tier are out of space: The page allocation can fall back to any node from any lower tier, whereas the demotion order doesn't allow that. The current kernel also don't provide any interfaces for the userspace to learn about the memory tier hierarchy in order to optimize its memory allocations. This patch series address the above by defining memory tiers explicitly. This patch introduce explicity memory tiers with ranks. The rank value of a memory tier is used to derive the demotion order between NUMA nodes. The memory tiers present in a system can be found at /sys/devices/system/memtier/memtierN/ The nodes which are part of a specific memory tier can be listed via /sys/devices/system/memtier/memtierN/nodelist "Rank" is an opaque value. Its absolute value doesn't have any special meaning. But the rank values of different memtiers can be compared with each other to determine the memory tier order. For example, if we have 3 memtiers: memtier0, memtier1, memiter2, and their rank values are 300, 200, 100, then the memory tier order is: memtier0 -> memtier2 -> memtier1, where memtier0 is the highest tier and memtier1 is the lowest tier. The rank value of each memtier should be unique. A higher rank memory tier will appear first in the demotion order than a lower rank memory tier. ie. while reclaim we choose a node in higher rank memory tier to demote pages to as compared to a node in a lower rank memory tier. For now we are not adding the dynamic number of memory tiers. But a future series supporting that is possible. Currently number of tiers supported is limitted to MAX_MEMORY_TIERS(3). When doing memory hotplug, if not added to a memory tier, the NUMA node gets added to DEFAULT_MEMORY_TIER(1). This patch is based on the proposal sent by Wei Xu <weixugc@xxxxxxxxxx> at [1]. [1] https://lore.kernel.org/linux-mm/CAAPL-u9Wv+nH1VOZTj=9p9S70Y3Qz3+63EkqncRDdHfubsrjfw@xxxxxxxxxxxxxx Suggested-by: Wei Xu <weixugc@xxxxxxxxxx> Signed-off-by: Jagdish Gediya <jvgediya@xxxxxxxxxxxxx> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx> --- include/linux/memory-tiers.h | 20 ++++ mm/Kconfig | 11 ++ mm/Makefile | 1 + mm/memory-tiers.c | 188 +++++++++++++++++++++++++++++++++++ 4 files changed, 220 insertions(+) create mode 100644 include/linux/memory-tiers.h create mode 100644 mm/memory-tiers.c diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h new file mode 100644 index 000000000000..e17f6b4ee177 --- /dev/null +++ b/include/linux/memory-tiers.h @@ -0,0 +1,20 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_MEMORY_TIERS_H +#define _LINUX_MEMORY_TIERS_H + +#ifdef CONFIG_TIERED_MEMORY + +#define MEMORY_TIER_HBM_GPU 0 +#define MEMORY_TIER_DRAM 1 +#define MEMORY_TIER_PMEM 2 + +#define MEMORY_RANK_HBM_GPU 300 +#define MEMORY_RANK_DRAM 200 +#define MEMORY_RANK_PMEM 100 + +#define DEFAULT_MEMORY_TIER MEMORY_TIER_DRAM +#define MAX_MEMORY_TIERS 3 + +#endif /* CONFIG_TIERED_MEMORY */ + +#endif diff --git a/mm/Kconfig b/mm/Kconfig index 169e64192e48..08a3d330740b 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -614,6 +614,17 @@ config ARCH_ENABLE_HUGEPAGE_MIGRATION config ARCH_ENABLE_THP_MIGRATION bool +config TIERED_MEMORY + bool "Support for explicit memory tiers" + def_bool n + depends on MIGRATION && NUMA + help + Support to split nodes into memory tiers explicitly and + to demote pages on reclaim to lower tiers. This option + also exposes sysfs interface to read nodes available in + specific tier and to move specific node among different + possible tiers. + config HUGETLB_PAGE_SIZE_VARIABLE def_bool n help diff --git a/mm/Makefile b/mm/Makefile index 6f9ffa968a1a..482557fbc9d1 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -92,6 +92,7 @@ obj-$(CONFIG_KFENCE) += kfence/ obj-$(CONFIG_FAILSLAB) += failslab.o obj-$(CONFIG_MEMTEST) += memtest.o obj-$(CONFIG_MIGRATION) += migrate.o +obj-$(CONFIG_TIERED_MEMORY) += memory-tiers.o obj-$(CONFIG_DEVICE_MIGRATION) += migrate_device.o obj-$(CONFIG_TRANSPARENT_HUGEPAGE) += huge_memory.o khugepaged.o obj-$(CONFIG_PAGE_COUNTER) += page_counter.o diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c new file mode 100644 index 000000000000..7de18d94a08d --- /dev/null +++ b/mm/memory-tiers.c @@ -0,0 +1,188 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <linux/types.h> +#include <linux/device.h> +#include <linux/nodemask.h> +#include <linux/slab.h> +#include <linux/memory-tiers.h> + +struct memory_tier { + struct list_head list; + struct device dev; + nodemask_t nodelist; + int rank; +}; + +#define to_memory_tier(device) container_of(device, struct memory_tier, dev) + +static struct bus_type memory_tier_subsys = { + .name = "memtier", + .dev_name = "memtier", +}; + +static DEFINE_MUTEX(memory_tier_lock); +static LIST_HEAD(memory_tiers); + + +static ssize_t nodelist_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct memory_tier *memtier = to_memory_tier(dev); + + return sysfs_emit(buf, "%*pbl\n", + nodemask_pr_args(&memtier->nodelist)); +} +static DEVICE_ATTR_RO(nodelist); + +static ssize_t rank_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct memory_tier *memtier = to_memory_tier(dev); + + return sysfs_emit(buf, "%d\n", memtier->rank); +} +static DEVICE_ATTR_RO(rank); + +static struct attribute *memory_tier_dev_attrs[] = { + &dev_attr_nodelist.attr, + &dev_attr_rank.attr, + NULL +}; + +static const struct attribute_group memory_tier_dev_group = { + .attrs = memory_tier_dev_attrs, +}; + +static const struct attribute_group *memory_tier_dev_groups[] = { + &memory_tier_dev_group, + NULL +}; + +static void memory_tier_device_release(struct device *dev) +{ + struct memory_tier *tier = to_memory_tier(dev); + + kfree(tier); +} + +/* + * Keep it simple by having direct mapping between + * tier index and rank value. + */ +static inline int get_rank_from_tier(unsigned int tier) +{ + switch (tier) { + case MEMORY_TIER_HBM_GPU: + return MEMORY_RANK_HBM_GPU; + case MEMORY_TIER_DRAM: + return MEMORY_RANK_DRAM; + case MEMORY_TIER_PMEM: + return MEMORY_RANK_PMEM; + } + + return 0; +} + +static void insert_memory_tier(struct memory_tier *memtier) +{ + struct list_head *ent; + struct memory_tier *tmp_memtier; + + list_for_each(ent, &memory_tiers) { + tmp_memtier = list_entry(ent, struct memory_tier, list); + if (tmp_memtier->rank < memtier->rank) { + list_add_tail(&memtier->list, ent); + return; + } + } + list_add_tail(&memtier->list, &memory_tiers); +} + +static struct memory_tier *register_memory_tier(unsigned int tier) +{ + int error; + struct memory_tier *memtier; + + if (tier >= MAX_MEMORY_TIERS) + return NULL; + + memtier = kzalloc(sizeof(struct memory_tier), GFP_KERNEL); + if (!memtier) + return NULL; + + memtier->dev.id = tier; + memtier->rank = get_rank_from_tier(tier); + memtier->dev.bus = &memory_tier_subsys; + memtier->dev.release = memory_tier_device_release; + memtier->dev.groups = memory_tier_dev_groups; + + insert_memory_tier(memtier); + + error = device_register(&memtier->dev); + if (error) { + list_del(&memtier->list); + put_device(&memtier->dev); + return NULL; + } + return memtier; +} + +__maybe_unused // temporay to prevent warnings during bisects +static void unregister_memory_tier(struct memory_tier *memtier) +{ + list_del(&memtier->list); + device_unregister(&memtier->dev); +} + +static ssize_t +max_tier_show(struct device *dev, struct device_attribute *attr, char *buf) +{ + return sysfs_emit(buf, "%d\n", MAX_MEMORY_TIERS); +} +static DEVICE_ATTR_RO(max_tier); + +static ssize_t +default_tier_show(struct device *dev, struct device_attribute *attr, char *buf) +{ + return sysfs_emit(buf, "memtier%d\n", DEFAULT_MEMORY_TIER); +} +static DEVICE_ATTR_RO(default_tier); + +static struct attribute *memory_tier_attrs[] = { + &dev_attr_max_tier.attr, + &dev_attr_default_tier.attr, + NULL +}; + +static const struct attribute_group memory_tier_attr_group = { + .attrs = memory_tier_attrs, +}; + +static const struct attribute_group *memory_tier_attr_groups[] = { + &memory_tier_attr_group, + NULL, +}; + +static int __init memory_tier_init(void) +{ + int ret; + struct memory_tier *memtier; + + ret = subsys_system_register(&memory_tier_subsys, memory_tier_attr_groups); + if (ret) + panic("%s() failed to register subsystem: %d\n", __func__, ret); + + /* + * Register only default memory tier to hide all empty + * memory tier from sysfs. + */ + memtier = register_memory_tier(DEFAULT_MEMORY_TIER); + if (!memtier) + panic("%s() failed to register memory tier: %d\n", __func__, ret); + + /* CPU only nodes are not part of memory tiers. */ + memtier->nodelist = node_states[N_MEMORY]; + + return 0; +} +subsys_initcall(memory_tier_init); + -- 2.36.1
