Re: [PATCH v14 04/10] mm/demotion/dax/kmem: Set node's abstract distance to MEMTIER_DEFAULT_DAX_ADISTANCE

From: Huang, Ying
Date: Sun Aug 14 2022 - 22:39:23 EST

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In reply to: Huang, Ying: "Re: [PATCH v14 04/10] mm/demotion/dax/kmem: Set node's abstract distance to MEMTIER_DEFAULT_DAX_ADISTANCE"
Next in thread: Aneesh Kumar K.V: "[PATCH v14 06/10] mm/demotion: Add pg_data_t member to track node memory tier details"
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"Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx> writes:

> By default, all nodes are assigned to the default memory tier which
> is the memory tier designated for nodes with DRAM
>
> Set dax kmem device node's tier to slower memory tier by assigning
> abstract distance to MEMTIER_DEFAULT_DAX_ADISTANCE. Low-level drivers
> like papr_scm or ACPI NFIT can initialize memory device type to a
> more accurate value based on device tree details or HMAT. If the
> kernel doesn't find the memory type initialized, a default slower
> memory type is assigned by the kmem driver.
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
> ---
> drivers/dax/kmem.c | 42 +++++++++++++++--
> include/linux/memory-tiers.h | 42 ++++++++++++++++-
> mm/memory-tiers.c | 91 +++++++++++++++++++++++++++---------
> 3 files changed, 149 insertions(+), 26 deletions(-)
>
> diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
> index a37622060fff..d88814f1c414 100644
> --- a/drivers/dax/kmem.c
> +++ b/drivers/dax/kmem.c
> @@ -11,9 +11,17 @@
> #include <linux/fs.h>
> #include <linux/mm.h>
> #include <linux/mman.h>
> +#include <linux/memory-tiers.h>
> #include "dax-private.h"
> #include "bus.h"
>
> +/*
> + * Default abstract distance assigned to the NUMA node onlined
> + * by DAX/kmem if the low level platform driver didn't initialize
> + * one for this NUMA node.
> + */
> +#define MEMTIER_DEFAULT_DAX_ADISTANCE (MEMTIER_ADISTANCE_DRAM * 2)

If my understanding were correct, this is targeting Optane DCPMM for
now. The measured results in the following paper is,

https://arxiv.org/pdf/2002.06018.pdf

Section: 2.1 Read/Write Latencies

"
For read access, the latency of DCPMM was 400.1% higher than that of
DRAM. For write access, it was 407.1% higher.
"

Section: 2.2 Read/Write Bandwidths

"
For read access, the throughput of DCPMM was 37.1% of DRAM. For write
access, it was 7.8%
"

According to the above data, I think the MEMTIER_DEFAULT_DAX_ADISTANCE
can be "5 * MEMTIER_ADISTANCE_DRAM".

Best Regards,
Huang, Ying

> +
> /* Memory resource name used for add_memory_driver_managed(). */
> static const char *kmem_name;
> /* Set if any memory will remain added when the driver will be unloaded. */
> @@ -41,6 +49,7 @@ struct dax_kmem_data {
> struct resource *res[];
> };
>
> +static struct memory_dev_type *dax_slowmem_type;
> static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
> {
> struct device *dev = &dev_dax->dev;
> @@ -79,11 +88,13 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
> return -EINVAL;
> }
>
> + init_node_memory_type(numa_node, dax_slowmem_type);
> +
> + rc = -ENOMEM;
> data = kzalloc(struct_size(data, res, dev_dax->nr_range), GFP_KERNEL);
> if (!data)
> - return -ENOMEM;
> + goto err_dax_kmem_data;
>
> - rc = -ENOMEM;
> data->res_name = kstrdup(dev_name(dev), GFP_KERNEL);
> if (!data->res_name)
> goto err_res_name;
> @@ -155,6 +166,8 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
> kfree(data->res_name);
> err_res_name:
> kfree(data);
> +err_dax_kmem_data:
> + clear_node_memory_type(numa_node, dax_slowmem_type);
> return rc;
> }
>
> @@ -162,6 +175,7 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
> static void dev_dax_kmem_remove(struct dev_dax *dev_dax)
> {
> int i, success = 0;
> + int node = dev_dax->target_node;
> struct device *dev = &dev_dax->dev;
> struct dax_kmem_data *data = dev_get_drvdata(dev);
>
> @@ -198,6 +212,14 @@ static void dev_dax_kmem_remove(struct dev_dax *dev_dax)
> kfree(data->res_name);
> kfree(data);
> dev_set_drvdata(dev, NULL);
> + /*
> + * Clear the memtype association on successful unplug.
> + * If not, we have memory blocks left which can be
> + * offlined/onlined later. We need to keep memory_dev_type
> + * for that. This implies this reference will be around
> + * till next reboot.
> + */
> + clear_node_memory_type(node, dax_slowmem_type);
> }
> }
> #else
> @@ -228,9 +250,22 @@ static int __init dax_kmem_init(void)
> if (!kmem_name)
> return -ENOMEM;
>
> + dax_slowmem_type = alloc_memory_type(MEMTIER_DEFAULT_DAX_ADISTANCE);
> + if (IS_ERR(dax_slowmem_type)) {
> + rc = PTR_ERR(dax_slowmem_type);
> + goto err_dax_slowmem_type;
> + }
> +
> rc = dax_driver_register(&device_dax_kmem_driver);
> if (rc)
> - kfree_const(kmem_name);
> + goto error_dax_driver;
> +
> + return rc;
> +
> +error_dax_driver:
> + destroy_memory_type(dax_slowmem_type);
> +err_dax_slowmem_type:
> + kfree_const(kmem_name);
> return rc;
> }
>
> @@ -239,6 +274,7 @@ static void __exit dax_kmem_exit(void)
> dax_driver_unregister(&device_dax_kmem_driver);
> if (!any_hotremove_failed)
> kfree_const(kmem_name);
> + destroy_memory_type(dax_slowmem_type);
> }
>
> MODULE_AUTHOR("Intel Corporation");
> diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
> index cc89876899a6..0c739508517a 100644
> --- a/include/linux/memory-tiers.h
> +++ b/include/linux/memory-tiers.h
> @@ -2,6 +2,9 @@
> #ifndef _LINUX_MEMORY_TIERS_H
> #define _LINUX_MEMORY_TIERS_H
>
> +#include <linux/types.h>
> +#include <linux/nodemask.h>
> +#include <linux/kref.h>
> /*
> * Each tier cover a abstrace distance chunk size of 128
> */
> @@ -13,12 +16,49 @@
> #define MEMTIER_ADISTANCE_DRAM (4 * MEMTIER_CHUNK_SIZE)
> #define MEMTIER_HOTPLUG_PRIO 100
>
> +struct memory_tier;
> +struct memory_dev_type {
> + /* list of memory types that are part of same tier as this type */
> + struct list_head tier_sibiling;
> + /* abstract distance for this specific memory type */
> + int adistance;
> + /* Nodes of same abstract distance */
> + nodemask_t nodes;
> + struct kref kref;
> + struct memory_tier *memtier;
> +};
> +
> #ifdef CONFIG_NUMA
> -#include <linux/types.h>
> extern bool numa_demotion_enabled;
> +struct memory_dev_type *alloc_memory_type(int adistance);
> +void destroy_memory_type(struct memory_dev_type *memtype);
> +void init_node_memory_type(int node, struct memory_dev_type *default_type);
> +void clear_node_memory_type(int node, struct memory_dev_type *memtype);
>
> #else
>
> #define numa_demotion_enabled false
> +/*
> + * CONFIG_NUMA implementation returns non NULL error.
> + */
> +static inline struct memory_dev_type *alloc_memory_type(int adistance)
> +{
> + return NULL;
> +}
> +
> +static inline void destroy_memory_type(struct memory_dev_type *memtype)
> +{
> +
> +}
> +
> +static inline void init_node_memory_type(int node, struct memory_dev_type *default_type)
> +{
> +
> +}
> +
> +static inline void clear_node_memory_type(int node, struct memory_dev_type *memtype)
> +{
> +
> +}
> #endif /* CONFIG_NUMA */
> #endif /* _LINUX_MEMORY_TIERS_H */
> diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
> index 05f05395468a..e52ccbcb2b27 100644
> --- a/mm/memory-tiers.c
> +++ b/mm/memory-tiers.c
> @@ -1,6 +1,4 @@
> // SPDX-License-Identifier: GPL-2.0
> -#include <linux/types.h>
> -#include <linux/nodemask.h>
> #include <linux/slab.h>
> #include <linux/lockdep.h>
> #include <linux/sysfs.h>
> @@ -21,27 +19,10 @@ struct memory_tier {
> int adistance_start;
> };
>
> -struct memory_dev_type {
> - /* list of memory types that are part of same tier as this type */
> - struct list_head tier_sibiling;
> - /* abstract distance for this specific memory type */
> - int adistance;
> - /* Nodes of same abstract distance */
> - nodemask_t nodes;
> - struct memory_tier *memtier;
> -};
> -
> static DEFINE_MUTEX(memory_tier_lock);
> static LIST_HEAD(memory_tiers);
> static struct memory_dev_type *node_memory_types[MAX_NUMNODES];
> -/*
> - * For now we can have 4 faster memory tiers with smaller adistance
> - * than default DRAM tier.
> - */
> -static struct memory_dev_type default_dram_type = {
> - .adistance = MEMTIER_ADISTANCE_DRAM,
> - .tier_sibiling = LIST_HEAD_INIT(default_dram_type.tier_sibiling),
> -};
> +static struct memory_dev_type *default_dram_type;
>
> static struct memory_tier *find_create_memory_tier(struct memory_dev_type *memtype)
> {
> @@ -87,6 +68,14 @@ static struct memory_tier *find_create_memory_tier(struct memory_dev_type *memty
> return new_memtier;
> }
>
> +static inline void __init_node_memory_type(int node, struct memory_dev_type *default_type)
> +{
> + if (!node_memory_types[node]) {
> + node_memory_types[node] = default_type;
> + kref_get(&default_type->kref);
> + }
> +}
> +
> static struct memory_tier *set_node_memory_tier(int node)
> {
> struct memory_tier *memtier;
> @@ -97,8 +86,7 @@ static struct memory_tier *set_node_memory_tier(int node)
> if (!node_state(node, N_MEMORY))
> return ERR_PTR(-EINVAL);
>
> - if (!node_memory_types[node])
> - node_memory_types[node] = &default_dram_type;
> + __init_node_memory_type(node, default_dram_type);
>
> memtype = node_memory_types[node];
> node_set(node, memtype->nodes);
> @@ -144,6 +132,57 @@ static bool clear_node_memory_tier(int node)
> return cleared;
> }
>
> +static void release_memtype(struct kref *kref)
> +{
> + struct memory_dev_type *memtype;
> +
> + memtype = container_of(kref, struct memory_dev_type, kref);
> + kfree(memtype);
> +}
> +
> +struct memory_dev_type *alloc_memory_type(int adistance)
> +{
> + struct memory_dev_type *memtype;
> +
> + memtype = kmalloc(sizeof(*memtype), GFP_KERNEL);
> + if (!memtype)
> + return ERR_PTR(-ENOMEM);
> +
> + memtype->adistance = adistance;
> + INIT_LIST_HEAD(&memtype->tier_sibiling);
> + memtype->nodes = NODE_MASK_NONE;
> + memtype->memtier = NULL;
> + kref_init(&memtype->kref);
> + return memtype;
> +}
> +EXPORT_SYMBOL_GPL(alloc_memory_type);
> +
> +void destroy_memory_type(struct memory_dev_type *memtype)
> +{
> + kref_put(&memtype->kref, release_memtype);
> +}
> +EXPORT_SYMBOL_GPL(destroy_memory_type);
> +
> +void init_node_memory_type(int node, struct memory_dev_type *default_type)
> +{
> +
> + mutex_lock(&memory_tier_lock);
> + __init_node_memory_type(node, default_type);
> + mutex_unlock(&memory_tier_lock);
> +}
> +EXPORT_SYMBOL_GPL(init_node_memory_type);
> +
> +void clear_node_memory_type(int node, struct memory_dev_type *memtype)
> +{
> + mutex_lock(&memory_tier_lock);
> + if (node_memory_types[node] == memtype) {
> + node_memory_types[node] = NULL;
> + kref_put(&memtype->kref, release_memtype);
> + }
> + mutex_unlock(&memory_tier_lock);
> +}
> +EXPORT_SYMBOL_GPL(clear_node_memory_type);
> +
> static int __meminit memtier_hotplug_callback(struct notifier_block *self,
> unsigned long action, void *_arg)
> {
> @@ -178,6 +217,14 @@ static int __init memory_tier_init(void)
> struct memory_tier *memtier;
>
> mutex_lock(&memory_tier_lock);
> + /*
> + * For now we can have 4 faster memory tiers with smaller adistance
> + * than default DRAM tier.
> + */
> + default_dram_type = alloc_memory_type(MEMTIER_ADISTANCE_DRAM);
> + if (!default_dram_type)
> + panic("%s() failed to allocate default DRAM tier\n", __func__);
> +
> /*
> * Look at all the existing N_MEMORY nodes and add them to
> * default memory tier or to a tier if we already have memory

Next message: Zhengchao Shao: "[PATCH net-next] net: rtnetlink: fix module reference count leak issue in rtnetlink_rcv_msg"
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In reply to: Huang, Ying: "Re: [PATCH v14 04/10] mm/demotion/dax/kmem: Set node's abstract distance to MEMTIER_DEFAULT_DAX_ADISTANCE"
Next in thread: Aneesh Kumar K.V: "[PATCH v14 06/10] mm/demotion: Add pg_data_t member to track node memory tier details"
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