On Tue, 2022-06-07 at 14:32 -0700, Yang Shi wrote: > On Fri, Jun 3, 2022 at 6:43 AM Aneesh Kumar K.V > <aneesh.kumar@xxxxxxxxxxxxx> wrote: > > > > 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. > > IMHO we should not need a new kernel config. If tiering is not present > then there is just one tier on the system. And tiering is a kind of > hardware configuration, the information could be shown regardless of > whether demotion/promotion is supported/enabled or not. I think so too. At least it appears unnecessary to let the user turn on/off it at configuration time. All the code should be enclosed by #if defined(CONFIG_NUMA) && defined(CONIFIG_MIGRATION). So we will not waste memory in small systems. Best Regards, Huang, Ying > > + > > 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 > >
