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Message-ID: <87352nifox.fsf@linux.ibm.com>
Date: Mon, 19 Jun 2023 21:53:42 +0530
From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>
To: Huang Ying <ying.huang@...el.com>, linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>,
Huang Ying <ying.huang@...el.com>, Wei Xu <weixugc@...gle.com>,
Alistair Popple <apopple@...dia.com>,
Dan Williams <dan.j.williams@...el.com>,
Dave Hansen <dave.hansen@...el.com>,
Davidlohr Bueso <dave@...olabs.net>,
Johannes Weiner <hannes@...xchg.org>,
Jonathan Cameron <Jonathan.Cameron@...wei.com>,
Michal Hocko <mhocko@...nel.org>,
Yang Shi <shy828301@...il.com>,
Rafael J Wysocki <rafael.j.wysocki@...el.com>
Subject: Re: [RFC 3/4] acpi, hmat: calculate abstract distance with HMAT
Huang Ying <ying.huang@...el.com> writes:
> A memory tiering abstract distance calculation algorithm based on ACPI
> HMAT is implemented. The basic idea is as follows.
>
> The performance attributes of system default DRAM nodes are recorded
> as the base line. Whose abstract distance is MEMTIER_ADISTANCE_DRAM.
> Then, the ratio of the abstract distance of a memory node (target) to
> MEMTIER_ADISTANCE_DRAM is scaled based on the ratio of the performance
> attributes of the node to that of the default DRAM nodes.
>
> Signed-off-by: "Huang, Ying" <ying.huang@...el.com>
> Cc: Aneesh Kumar K.V <aneesh.kumar@...ux.ibm.com>
> Cc: Wei Xu <weixugc@...gle.com>
> Cc: Alistair Popple <apopple@...dia.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Dave Hansen <dave.hansen@...el.com>
> Cc: Davidlohr Bueso <dave@...olabs.net>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Cc: Michal Hocko <mhocko@...nel.org>
> Cc: Yang Shi <shy828301@...il.com>
> Cc: Rafael J Wysocki <rafael.j.wysocki@...el.com>
> ---
> drivers/acpi/numa/hmat.c | 124 ++++++++++++++++++++++++++++++++++-
> include/linux/memory-tiers.h | 2 +
> mm/memory-tiers.c | 2 +-
> 3 files changed, 126 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/acpi/numa/hmat.c b/drivers/acpi/numa/hmat.c
> index 2dee0098f1a9..21e4deb581ad 100644
> --- a/drivers/acpi/numa/hmat.c
> +++ b/drivers/acpi/numa/hmat.c
> @@ -24,6 +24,7 @@
> #include <linux/node.h>
> #include <linux/sysfs.h>
> #include <linux/dax.h>
> +#include <linux/memory-tiers.h>
>
> static u8 hmat_revision;
> static int hmat_disable __initdata;
> @@ -759,6 +760,123 @@ static int hmat_callback(struct notifier_block *self,
> return NOTIFY_OK;
> }
>
> +static int hmat_adistance_disabled;
> +static struct node_hmem_attrs default_dram_attrs;
> +
> +static void dump_hmem_attrs(struct node_hmem_attrs *attrs)
> +{
> + pr_cont("read_latency: %u, write_latency: %u, read_bandwidth: %u, write_bandwidth: %u\n",
> + attrs->read_latency, attrs->write_latency,
> + attrs->read_bandwidth, attrs->write_bandwidth);
> +}
> +
> +static void disable_hmat_adistance_algorithm(void)
> +{
> + hmat_adistance_disabled = true;
> +}
> +
> +static int hmat_init_default_dram_attrs(void)
> +{
> + struct memory_target *target;
> + struct node_hmem_attrs *attrs;
> + int nid, pxm;
> + int nid_dram = NUMA_NO_NODE;
> +
> + if (default_dram_attrs.read_latency +
> + default_dram_attrs.write_latency != 0)
> + return 0;
> +
> + if (!default_dram_type)
> + return -EIO;
> +
> + for_each_node_mask(nid, default_dram_type->nodes) {
> + pxm = node_to_pxm(nid);
> + target = find_mem_target(pxm);
> + if (!target)
> + continue;
> + attrs = &target->hmem_attrs[1];
> + if (nid_dram == NUMA_NO_NODE) {
> + if (attrs->read_latency + attrs->write_latency == 0 ||
> + attrs->read_bandwidth + attrs->write_bandwidth == 0) {
> + pr_info("hmat: invalid hmem attrs for default DRAM node: %d,\n",
> + nid);
> + pr_info(" ");
> + dump_hmem_attrs(attrs);
> + pr_info(" disable hmat based abstract distance algorithm.\n");
> + disable_hmat_adistance_algorithm();
> + return -EIO;
> + }
> + nid_dram = nid;
> + default_dram_attrs = *attrs;
> + continue;
> + }
> + if (abs(attrs->read_latency - default_dram_attrs.read_latency) * 10 >
> + default_dram_attrs.read_latency ||
> + abs(attrs->write_latency - default_dram_attrs.write_latency) * 10 >
> + default_dram_attrs.write_latency ||
> + abs(attrs->read_bandwidth - default_dram_attrs.read_bandwidth) * 10 >
> + default_dram_attrs.read_bandwidth) {
> + pr_info("hmat: hmem attrs for DRAM nodes mismatch.\n");
> + pr_info(" node %d:", nid_dram);
> + dump_hmem_attrs(&default_dram_attrs);
> + pr_info(" node %d:", nid);
> + dump_hmem_attrs(attrs);
> + pr_info(" disable hmat based abstract distance algorithm.\n");
> + disable_hmat_adistance_algorithm();
> + return -EIO;
> + }
What is this check about? what is the significance of 10? Can you add
the details as a code comment ?
> + }
> +
> + return 0;
> +}
> +
> +static int hmat_calculate_adistance(struct notifier_block *self,
> + unsigned long nid, void *data)
> +{
> + static DECLARE_BITMAP(p_nodes, MAX_NUMNODES);
> + struct memory_target *target;
> + struct node_hmem_attrs *attrs;
> + int *adist = data;
> + int pxm;
> +
> + if (hmat_adistance_disabled)
> + return NOTIFY_OK;
> +
> + pxm = node_to_pxm(nid);
> + target = find_mem_target(pxm);
> + if (!target)
> + return NOTIFY_OK;
> +
> + if (hmat_init_default_dram_attrs())
> + return NOTIFY_OK;
> +
> + mutex_lock(&target_lock);
> + hmat_update_target_attrs(target, p_nodes, 1);
> + mutex_unlock(&target_lock);
> +
> + attrs = &target->hmem_attrs[1];
> +
> + if (attrs->read_latency + attrs->write_latency == 0 ||
> + attrs->read_bandwidth + attrs->write_bandwidth == 0)
> + return NOTIFY_OK;
> +
> + *adist = MEMTIER_ADISTANCE_DRAM *
> + (attrs->read_latency + attrs->write_latency) /
> + (default_dram_attrs.read_latency +
> + default_dram_attrs.write_latency) *
> + (default_dram_attrs.read_bandwidth +
> + default_dram_attrs.write_bandwidth) /
> + (attrs->read_bandwidth + attrs->write_bandwidth);
Can you write a comment describing how we use all these attributes in
deriving the abstract distance value?
> +
> + return NOTIFY_STOP;
> +}
> +
> +static __meminitdata struct notifier_block hmat_adist_nb =
> +{
> + .notifier_call = hmat_calculate_adistance,
> + .priority = 100,
> +};
> +
> static __init void hmat_free_structures(void)
> {
> struct memory_target *target, *tnext;
> @@ -801,6 +919,7 @@ static __init int hmat_init(void)
> struct acpi_table_header *tbl;
> enum acpi_hmat_type i;
> acpi_status status;
> + int usage;
>
> if (srat_disabled() || hmat_disable)
> return 0;
> @@ -841,8 +960,11 @@ static __init int hmat_init(void)
> hmat_register_targets();
>
> /* Keep the table and structures if the notifier may use them */
> - if (!hotplug_memory_notifier(hmat_callback, HMAT_CALLBACK_PRI))
> + usage = !hotplug_memory_notifier(hmat_callback, HMAT_CALLBACK_PRI);
> + usage += !register_mt_adistance_algorithm(&hmat_adist_nb);
> + if (usage)
> return 0;
> +
> out_put:
> hmat_free_structures();
> acpi_put_table(tbl);
> diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
> index c6429e624244..9377239c8d34 100644
> --- a/include/linux/memory-tiers.h
> +++ b/include/linux/memory-tiers.h
> @@ -33,6 +33,7 @@ struct memory_dev_type {
>
> #ifdef CONFIG_NUMA
> extern bool numa_demotion_enabled;
> +extern struct memory_dev_type *default_dram_type;
> 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);
> @@ -64,6 +65,7 @@ static inline bool node_is_toptier(int node)
> #else
>
> #define numa_demotion_enabled false
> +#define default_dram_type NULL
> /*
> * CONFIG_NUMA implementation returns non NULL error.
> */
> diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
> index fb5398e710cc..3aabc7240402 100644
> --- a/mm/memory-tiers.c
> +++ b/mm/memory-tiers.c
> @@ -37,7 +37,7 @@ struct node_memory_type_map {
> static DEFINE_MUTEX(memory_tier_lock);
> static LIST_HEAD(memory_tiers);
> static struct node_memory_type_map node_memory_types[MAX_NUMNODES];
> -static struct memory_dev_type *default_dram_type;
> +struct memory_dev_type *default_dram_type;
>
> static struct bus_type memory_tier_subsys = {
> .name = "memory_tiering",
> --
> 2.39.2
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