"Ho-Ren (Jack) Chuang" <horenchuang@xxxxxxxxxxxxx> writes:
> The current implementation treats emulated memory devices, such as
> CXL1.1 type3 memory, as normal DRAM when they are emulated as normal memory
> (E820_TYPE_RAM). However, these emulated devices have different
> characteristics than traditional DRAM, making it important to
> distinguish them. Thus, we modify the tiered memory initialization process
> to introduce a delay specifically for CPUless NUMA nodes. This delay
> ensures that the memory tier initialization for these nodes is deferred
> until HMAT information is obtained during the boot process. Finally,
> demotion tables are recalculated at the end.
>
> More details:
You have done several stuff in one patch. So you need "more details".
You may separate them into multiple patches. One for echo "*" below.
But I have no strong opinion on that.
> * late_initcall(memory_tier_late_init);
> Some device drivers may have initialized memory tiers between
> `memory_tier_init()` and `memory_tier_late_init()`, potentially bringing
> online memory nodes and configuring memory tiers. They should be excluded
> in the late init.
>
> * Abstract common functions into `mt_find_alloc_memory_type()`
> Since different memory devices require finding or allocating a memory type,
> these common steps are abstracted into a single function,
> `mt_find_alloc_memory_type()`, enhancing code scalability and conciseness.
>
> * Handle cases where there is no HMAT when creating memory tiers
> There is a scenario where a CPUless node does not provide HMAT information.
> If no HMAT is specified, it falls back to using the default DRAM tier.
>
> * Change adist calculation code to use another new lock, `mt_perf_lock`.
> In the current implementation, iterating through CPUlist nodes requires
> holding the `memory_tier_lock`. However, `mt_calc_adistance()` will end up
> trying to acquire the same lock, leading to a potential deadlock.
> Therefore, we propose introducing a standalone `mt_perf_lock` to protect
> `default_dram_perf`. This approach not only avoids deadlock but also
> prevents holding a large lock simultaneously.
>
> * Upgrade `set_node_memory_tier` to support additional cases, including
> default DRAM, late CPUless, and hot-plugged initializations.
> To cover hot-plugged memory nodes, `mt_calc_adistance()` and
> `mt_find_alloc_memory_type()` are moved into `set_node_memory_tier()` to
> handle cases where memtype is not initialized and where HMAT information is
> available.
>
> * Introduce `default_memory_types` for those memory types that are not
> initialized by device drivers.
> Because late initialized memory and default DRAM memory need to be managed,
> a default memory type is created for storing all memory types that are
> not initialized by device drivers and as a fallback.
>
> Signed-off-by: Ho-Ren (Jack) Chuang <horenchuang@xxxxxxxxxxxxx>
> Signed-off-by: Hao Xiang <hao.xiang@xxxxxxxxxxxxx>
> ---
> drivers/dax/kmem.c | 13 +----
> include/linux/memory-tiers.h | 7 +++
> mm/memory-tiers.c | 94 +++++++++++++++++++++++++++++++++---
> 3 files changed, 95 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
> index 42ee360cf4e3..de1333aa7b3e 100644
> --- a/drivers/dax/kmem.c
> +++ b/drivers/dax/kmem.c
> @@ -55,21 +55,10 @@ static LIST_HEAD(kmem_memory_types);
>
> static struct memory_dev_type *kmem_find_alloc_memory_type(int adist)
> {
> - bool found = false;
> struct memory_dev_type *mtype;
>
> mutex_lock(&kmem_memory_type_lock);
> - list_for_each_entry(mtype, &kmem_memory_types, list) {
> - if (mtype->adistance == adist) {
> - found = true;
> - break;
> - }
> - }
> - if (!found) {
> - mtype = alloc_memory_type(adist);
> - if (!IS_ERR(mtype))
> - list_add(&mtype->list, &kmem_memory_types);
> - }
> + mtype = mt_find_alloc_memory_type(adist, &kmem_memory_types);
> mutex_unlock(&kmem_memory_type_lock);
>
> return mtype;
It seems that there's some miscommunication about my previous comments
about this. What I suggested is to create one separate patch, which
moves mt_find_alloc_memory_type() and mt_put_memory_types() into
memory-tiers.c. And make this patch the first one of the series.
> diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
> index 69e781900082..b2135334ac18 100644
> --- a/include/linux/memory-tiers.h
> +++ b/include/linux/memory-tiers.h
> @@ -48,6 +48,8 @@ int mt_calc_adistance(int node, int *adist);
> int mt_set_default_dram_perf(int nid, struct access_coordinate *perf,
> const char *source);
> int mt_perf_to_adistance(struct access_coordinate *perf, int *adist);
> +struct memory_dev_type *mt_find_alloc_memory_type(int adist,
> + struct list_head *memory_types);
> #ifdef CONFIG_MIGRATION
> int next_demotion_node(int node);
> void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *targets);
> @@ -136,5 +138,10 @@ static inline int mt_perf_to_adistance(struct access_coordinate *perf, int *adis
> {
> return -EIO;
> }
> +
> +struct memory_dev_type *mt_find_alloc_memory_type(int adist, struct list_head *memory_types)
> +{
> + return NULL;
> +}
> #endif /* CONFIG_NUMA */
> #endif /* _LINUX_MEMORY_TIERS_H */
> diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
> index 0537664620e5..d9b96b21b65a 100644
> --- a/mm/memory-tiers.c
> +++ b/mm/memory-tiers.c
> @@ -6,6 +6,7 @@
> #include <linux/memory.h>
> #include <linux/memory-tiers.h>
> #include <linux/notifier.h>
> +#include <linux/acpi.h>
We don't need this anymore.
> #include "internal.h"
>
> @@ -36,6 +37,11 @@ struct node_memory_type_map {
>
> static DEFINE_MUTEX(memory_tier_lock);
> static LIST_HEAD(memory_tiers);
> +/*
> + * The list is used to store all memory types that are not created
> + * by a device driver.
> + */
> +static LIST_HEAD(default_memory_types);
> static struct node_memory_type_map node_memory_types[MAX_NUMNODES];
> struct memory_dev_type *default_dram_type;
>
> @@ -505,7 +511,8 @@ static inline void __init_node_memory_type(int node, struct memory_dev_type *mem
> static struct memory_tier *set_node_memory_tier(int node)
> {
> struct memory_tier *memtier;
> - struct memory_dev_type *memtype;
> + struct memory_dev_type *memtype, *mtype = NULL;
It seems unnecessary to introduce another variable, just use memtype?
> + int adist = MEMTIER_ADISTANCE_DRAM;
> pg_data_t *pgdat = NODE_DATA(node);
>
>
> @@ -514,7 +521,18 @@ static struct memory_tier *set_node_memory_tier(int node)
> if (!node_state(node, N_MEMORY))
> return ERR_PTR(-EINVAL);
>
> - __init_node_memory_type(node, default_dram_type);
> + mt_calc_adistance(node, &adist);
> + if (adist != MEMTIER_ADISTANCE_DRAM &&
> + node_memory_types[node].memtype == NULL) {
> + mtype = mt_find_alloc_memory_type(adist, &default_memory_types);
> + if (IS_ERR(mtype)) {
> + mtype = default_dram_type;
> + pr_info("Failed to allocate a memory type. Fall back.\n");
> + }
> + } else
> + mtype = default_dram_type;
This can be simplified to
mt_calc_adistance(node, &adist);
if (node_memory_types[node].memtype == NULL) {
mtype = mt_find_alloc_memory_type(adist, &default_memory_types);
if (IS_ERR(mtype)) {
mtype = default_dram_type;
pr_info("Failed to allocate a memory type. Fall back.\n");
}
}
> + __init_node_memory_type(node, mtype);
>
> memtype = node_memory_types[node].memtype;
> node_set(node, memtype->nodes);
> @@ -623,6 +641,55 @@ void clear_node_memory_type(int node, struct memory_dev_type *memtype)
> }
> EXPORT_SYMBOL_GPL(clear_node_memory_type);
>
> +struct memory_dev_type *mt_find_alloc_memory_type(int adist, struct list_head *memory_types)
> +{
> + bool found = false;
> + struct memory_dev_type *mtype;
> +
> + list_for_each_entry(mtype, memory_types, list) {
> + if (mtype->adistance == adist) {
> + found = true;
> + break;
> + }
> + }
> + if (!found) {
> + mtype = alloc_memory_type(adist);
> + if (!IS_ERR(mtype))
> + list_add(&mtype->list, memory_types);
> + }
> +
> + return mtype;
> +}
> +EXPORT_SYMBOL_GPL(mt_find_alloc_memory_type);
> +
> +/*
> + * This is invoked via late_initcall() to create
> + * CPUless memory tiers after HMAT info is ready or
> + * when there is no HMAT.
Better to avoid HMAT in general code. How about something as below?
This is invoked via late_initcall() to initialize memory tiers for
CPU-less memory nodes after drivers initialization. Which is
expect to provide adistance algorithms.
> + */
> +static int __init memory_tier_late_init(void)
> +{
> + int nid;
> +
> + mutex_lock(&memory_tier_lock);
> + for_each_node_state(nid, N_MEMORY)
> + if (!node_state(nid, N_CPU) &&
> + node_memory_types[nid].memtype == NULL)
> + /*
> + * Some device drivers may have initialized memory tiers
> + * between `memory_tier_init()` and `memory_tier_late_init()`,
> + * potentially bringing online memory nodes and
> + * configuring memory tiers. Exclude them here.
> + */
> + set_node_memory_tier(nid);
> +
> + establish_demotion_targets();
> + mutex_unlock(&memory_tier_lock);
> +
> + return 0;
> +}
> +late_initcall(memory_tier_late_init);
> +
> static void dump_hmem_attrs(struct access_coordinate *coord, const char *prefix)
> {
> pr_info(
> @@ -631,12 +698,16 @@ static void dump_hmem_attrs(struct access_coordinate *coord, const char *prefix)
> coord->read_bandwidth, coord->write_bandwidth);
> }
>
> +/*
> + * The lock is used to protect the default_dram_perf.
> + */
> +static DEFINE_MUTEX(mt_perf_lock);
Miscommunication here too. Should be moved to near the
"default_dram_perf" definition. And it protects not only
default_dram_perf.
> int mt_set_default_dram_perf(int nid, struct access_coordinate *perf,
> const char *source)
> {
> int rc = 0;
>
> - mutex_lock(&memory_tier_lock);
> + mutex_lock(&mt_perf_lock);
> if (default_dram_perf_error) {
> rc = -EIO;
> goto out;
> @@ -684,7 +755,7 @@ int mt_set_default_dram_perf(int nid, struct access_coordinate *perf,
> }
>
> out:
> - mutex_unlock(&memory_tier_lock);
> + mutex_unlock(&mt_perf_lock);
> return rc;
> }
>
> @@ -700,7 +771,7 @@ int mt_perf_to_adistance(struct access_coordinate *perf, int *adist)
> perf->read_bandwidth + perf->write_bandwidth == 0)
> return -EINVAL;
>
> - mutex_lock(&memory_tier_lock);
> + mutex_lock(&mt_perf_lock);
> /*
> * The abstract distance of a memory node is in direct proportion to
> * its memory latency (read + write) and inversely proportional to its
> @@ -713,7 +784,7 @@ int mt_perf_to_adistance(struct access_coordinate *perf, int *adist)
> (default_dram_perf.read_latency + default_dram_perf.write_latency) *
> (default_dram_perf.read_bandwidth + default_dram_perf.write_bandwidth) /
> (perf->read_bandwidth + perf->write_bandwidth);
> - mutex_unlock(&memory_tier_lock);
> + mutex_unlock(&mt_perf_lock);
>
> return 0;
> }
> @@ -826,7 +897,8 @@ static int __init memory_tier_init(void)
> * 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);
> + default_dram_type = mt_find_alloc_memory_type(
> + MEMTIER_ADISTANCE_DRAM, &default_memory_types);
> if (IS_ERR(default_dram_type))
> panic("%s() failed to allocate default DRAM tier\n", __func__);
>
> @@ -836,6 +908,14 @@ static int __init memory_tier_init(void)
> * types assigned.
> */
> for_each_node_state(node, N_MEMORY) {
> + if (!node_state(node, N_CPU))
> + /*
> + * Defer memory tier initialization on CPUless numa nodes.
> + * These will be initialized after firmware and devices are
> + * initialized.
> + */
> + continue;
> +
> memtier = set_node_memory_tier(node);
> if (IS_ERR(memtier))
> /*
--
Best Regards,
Huang, Ying
