On Wed, Mar 20, 2024 at 12:15 AM Huang, Ying <ying.huang@xxxxxxxxx> wrote:
>
> "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.
>
I will make mt_find_alloc/mt_put_memory_type changes as
a separate patch and the first of my patch series. Thanks.
> > 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.
>
Thanks. I will remove it.
> > #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?
>
Yes, I will consolidate them.
> > + 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");
> }
> }
>
Sounds good! I will do.
> > + __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.
>
Got it. Thanks.
"
This is invoked via `late_initcall()` to initialize memory tiers for
CPU-less memory nodes after driver initialization, which is
expected 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.
>
I will move it closer to default_dram_perf*.
And change it to:
+/*
+ * The lock is used to protect 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
--
Best regards,
Ho-Ren (Jack) Chuang
莊賀任
