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References: <20240312061729.1997111-1-horenchuang@bytedance.com>
 <20240312061729.1997111-2-horenchuang@bytedance.com> <874jdb4xk8.fsf@yhuang6-desk2.ccr.corp.intel.com>
In-Reply-To: <874jdb4xk8.fsf@yhuang6-desk2.ccr.corp.intel.com>
From: "Ho-Ren (Jack) Chuang" <horenchuang@bytedance.com>
Date: Wed, 13 Mar 2024 01:16:27 -0700
Message-ID: <CAKPbEqpTNN5GKKCXmyTv0szpL-N1pdKFZYPHCJjyhgpKZGMiWw@mail.gmail.com>
Subject: Re: [External] Re: [PATCH v2 1/1] memory tier: acpi/hmat: create
 CPUless memory tiers after obtaining HMAT info
To: "Huang, Ying" <ying.huang@intel.com>
Cc: Gregory Price <gourry.memverge@gmail.com>, aneesh.kumar@linux.ibm.com, mhocko@suse.com, 
	tj@kernel.org, john@jagalactic.com, Eishan Mirakhur <emirakhur@micron.com>, 
	Vinicius Tavares Petrucci <vtavarespetr@micron.com>, Ravis OpenSrc <Ravis.OpenSrc@micron.com>, 
	Alistair Popple <apopple@nvidia.com>, "Rafael J. Wysocki" <rafael@kernel.org>, Len Brown <lenb@kernel.org>, 
	Dan Williams <dan.j.williams@intel.com>, Vishal Verma <vishal.l.verma@intel.com>, 
	Dave Jiang <dave.jiang@intel.com>, Andrew Morton <akpm@linux-foundation.org>, 
	Jonathan Cameron <Jonathan.Cameron@huawei.com>, linux-acpi@vger.kernel.org, 
	linux-kernel@vger.kernel.org, nvdimm@lists.linux.dev, 
	linux-cxl@vger.kernel.org, linux-mm@kvack.org, 
	"Ho-Ren (Jack) Chuang" <horenc@vt.edu>, "Ho-Ren (Jack) Chuang" <horenchuang@gmail.com>, qemu-devel@nongnu.org, 
	Hao Xiang <hao.xiang@bytedance.com>
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On Tue, Mar 12, 2024 at 2:21=E2=80=AFAM Huang, Ying <ying.huang@intel.com> =
wrote:
>
> "Ho-Ren (Jack) Chuang" <horenchuang@bytedance.com> writes:
>
> > The current implementation treats emulated memory devices, such as
> > CXL1.1 type3 memory, as normal DRAM when they are emulated as normal me=
mory
> > (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 proc=
ess
> > 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.
> >
> > * Abstract common functions into `find_alloc_memory_type()`
>
> We should move kmem_put_memory_types() (renamed to
> mt_put_memory_types()?) too.  This can be put in a separate patch.
>

Will do! Thanks,


>
> > Since different memory devices require finding or allocating a memory t=
ype,
> > these common steps are abstracted into a single function,
> > `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 informat=
ion.
> > 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 protec=
t
> > `default_dram_perf`. This approach not only avoids deadlock but also
> > prevents holding a large lock simultaneously.
> >
> > Signed-off-by: Ho-Ren (Jack) Chuang <horenchuang@bytedance.com>
> > Signed-off-by: Hao Xiang <hao.xiang@bytedance.com>
> > ---
> >  drivers/acpi/numa/hmat.c     | 11 ++++++
> >  drivers/dax/kmem.c           | 13 +------
> >  include/linux/acpi.h         |  6 ++++
> >  include/linux/memory-tiers.h |  8 +++++
> >  mm/memory-tiers.c            | 70 +++++++++++++++++++++++++++++++++---
> >  5 files changed, 92 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/acpi/numa/hmat.c b/drivers/acpi/numa/hmat.c
> > index d6b85f0f6082..28812ec2c793 100644
> > --- a/drivers/acpi/numa/hmat.c
> > +++ b/drivers/acpi/numa/hmat.c
> > @@ -38,6 +38,8 @@ static LIST_HEAD(targets);
> >  static LIST_HEAD(initiators);
> >  static LIST_HEAD(localities);
> >
> > +static LIST_HEAD(hmat_memory_types);
> > +
>
> HMAT isn't a device driver for some memory devices.  So I don't think we
> should manage memory types in HMAT.

I can put it back in memory-tier.c. How about the list? Do we still
need to keep a separate list for storing late_inited memory nodes?
And how about the list name if we need to remove the prefix "hmat_"?


> Instead, if the memory_type of a
> node isn't set by the driver, we should manage it in memory-tier.c as
> fallback.
>

Do you mean some device drivers may init memory tiers between
memory_tier_init() and late_initcall(memory_tier_late_init);?
And this is the reason why you mention to exclude
"node_memory_types[nid].memtype !=3D NULL" in memory_tier_late_init().
Is my understanding correct?

> >  static DEFINE_MUTEX(target_lock);
> >
> >  /*
> > @@ -149,6 +151,12 @@ int acpi_get_genport_coordinates(u32 uid,
> >  }
> >  EXPORT_SYMBOL_NS_GPL(acpi_get_genport_coordinates, CXL);
> >
> > +struct memory_dev_type *hmat_find_alloc_memory_type(int adist)
> > +{
> > +     return find_alloc_memory_type(adist, &hmat_memory_types);
> > +}
> > +EXPORT_SYMBOL_GPL(hmat_find_alloc_memory_type);
> > +
> >  static __init void alloc_memory_initiator(unsigned int cpu_pxm)
> >  {
> >       struct memory_initiator *initiator;
> > @@ -1038,6 +1046,9 @@ static __init int hmat_init(void)
> >       if (!hmat_set_default_dram_perf())
> >               register_mt_adistance_algorithm(&hmat_adist_nb);
> >
> > +     /* Post-create CPUless memory tiers after getting HMAT info */
> > +     memory_tier_late_init();
> > +
>
> This should be called in memory-tier.c via
>
> late_initcall(memory_tier_late_init);
>
> Then, we don't need hmat to call it.
>

Thanks. Learned!


> >       return 0;
> >  out_put:
> >       hmat_free_structures();
> > diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
> > index 42ee360cf4e3..aee17ab59f4f 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 =3D false;
> >       struct memory_dev_type *mtype;
> >
> >       mutex_lock(&kmem_memory_type_lock);
> > -     list_for_each_entry(mtype, &kmem_memory_types, list) {
> > -             if (mtype->adistance =3D=3D adist) {
> > -                     found =3D true;
> > -                     break;
> > -             }
> > -     }
> > -     if (!found) {
> > -             mtype =3D alloc_memory_type(adist);
> > -             if (!IS_ERR(mtype))
> > -                     list_add(&mtype->list, &kmem_memory_types);
> > -     }
> > +     mtype =3D find_alloc_memory_type(adist, &kmem_memory_types);
> >       mutex_unlock(&kmem_memory_type_lock);
> >
> >       return mtype;
> > diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> > index b7165e52b3c6..3f927ff01f02 100644
> > --- a/include/linux/acpi.h
> > +++ b/include/linux/acpi.h
> > @@ -434,12 +434,18 @@ int thermal_acpi_critical_trip_temp(struct acpi_d=
evice *adev, int *ret_temp);
> >
> >  #ifdef CONFIG_ACPI_HMAT
> >  int acpi_get_genport_coordinates(u32 uid, struct access_coordinate *co=
ord);
> > +struct memory_dev_type *hmat_find_alloc_memory_type(int adist);
> >  #else
> >  static inline int acpi_get_genport_coordinates(u32 uid,
> >                                              struct access_coordinate *=
coord)
> >  {
> >       return -EOPNOTSUPP;
> >  }
> > +
> > +static inline struct memory_dev_type *hmat_find_alloc_memory_type(int =
adist)
> > +{
> > +     return NULL;
> > +}
> >  #endif
> >
> >  #ifdef CONFIG_ACPI_NUMA
> > diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.=
h
> > index 69e781900082..4bc2596c5774 100644
> > --- a/include/linux/memory-tiers.h
> > +++ b/include/linux/memory-tiers.h
> > @@ -48,6 +48,9 @@ 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 *find_alloc_memory_type(int adist,
> > +                                                     struct list_head =
*memory_types);
> > +void memory_tier_late_init(void);
> >  #ifdef CONFIG_MIGRATION
> >  int next_demotion_node(int node);
> >  void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *targets);
> > @@ -136,5 +139,10 @@ static inline int mt_perf_to_adistance(struct acce=
ss_coordinate *perf, int *adis
> >  {
> >       return -EIO;
> >  }
> > +
> > +static inline void memory_tier_late_init(void)
> > +{
> > +
> > +}
> >  #endif       /* CONFIG_NUMA */
> >  #endif  /* _LINUX_MEMORY_TIERS_H */
> > diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
> > index 0537664620e5..79f748d60e6f 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>
> >
> >  #include "internal.h"
> >
> > @@ -35,6 +36,7 @@ struct node_memory_type_map {
> >  };
> >
> >  static DEFINE_MUTEX(memory_tier_lock);
> > +static DEFINE_MUTEX(mt_perf_lock);
>
> Please add comments about what it protects.  And put it near the data
> structure it protects.
>

Where is better for me to add comments for this? Code? Patch description?
Will put it closer to the protected data. Thanks.


> >  static LIST_HEAD(memory_tiers);
> >  static struct node_memory_type_map node_memory_types[MAX_NUMNODES];
> >  struct memory_dev_type *default_dram_type;
> > @@ -623,6 +625,58 @@ void clear_node_memory_type(int node, struct memor=
y_dev_type *memtype)
> >  }
> >  EXPORT_SYMBOL_GPL(clear_node_memory_type);
> >
> > +struct memory_dev_type *find_alloc_memory_type(int adist, struct list_=
head *memory_types)
> > +{
> > +     bool found =3D false;
> > +     struct memory_dev_type *mtype;
> > +
> > +     list_for_each_entry(mtype, memory_types, list) {
> > +             if (mtype->adistance =3D=3D adist) {
> > +                     found =3D true;
> > +                     break;
> > +             }
> > +     }
> > +     if (!found) {
> > +             mtype =3D alloc_memory_type(adist);
> > +             if (!IS_ERR(mtype))
> > +                     list_add(&mtype->list, memory_types);
> > +     }
> > +
> > +     return mtype;
> > +}
> > +EXPORT_SYMBOL_GPL(find_alloc_memory_type);
> > +
> > +static void memory_tier_late_create(int node)
> > +{
> > +     struct memory_dev_type *mtype =3D NULL;
> > +     int adist =3D MEMTIER_ADISTANCE_DRAM;
> > +
> > +     mt_calc_adistance(node, &adist);
> > +     if (adist !=3D MEMTIER_ADISTANCE_DRAM) {
>
> We can manage default_dram_type() via find_alloc_memory_type()
> too.
>
> And, if "node_memory_types[node].memtype =3D=3D NULL", we can call
> mt_calc_adistance(node, &adist) and find_alloc_memory_type() in
> set_node_memory_tier().  Then, we can cover hotpluged memory node too.
>
> > +             mtype =3D hmat_find_alloc_memory_type(adist);
> > +             if (!IS_ERR(mtype))
> > +                     __init_node_memory_type(node, mtype);
> > +             else
> > +                     pr_err("Failed to allocate a memory type at %s()\=
n", __func__);
> > +     }
> > +
> > +     set_node_memory_tier(node);
> > +}
> > +
> > +void 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))
>
> We should exclude "node_memory_types[nid].memtype !=3D NULL".  Some memor=
y
> nodes may be onlined by some device drivers and setup memory tiers
> already.
>
> > +                     memory_tier_late_create(nid);
> > +
> > +     establish_demotion_targets();
> > +     mutex_unlock(&memory_tier_lock);
> > +}
> > +EXPORT_SYMBOL_GPL(memory_tier_late_init);
> > +
> >  static void dump_hmem_attrs(struct access_coordinate *coord, const cha=
r *prefix)
> >  {
> >       pr_info(
> > @@ -636,7 +690,7 @@ int mt_set_default_dram_perf(int nid, struct access=
_coordinate *perf,
> >  {
> >       int rc =3D 0;
> >
> > -     mutex_lock(&memory_tier_lock);
> > +     mutex_lock(&mt_perf_lock);
> >       if (default_dram_perf_error) {
> >               rc =3D -EIO;
> >               goto out;
> > @@ -684,7 +738,7 @@ 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 +754,7 @@ int mt_perf_to_adistance(struct access_coordinate *=
perf, int *adist)
> >           perf->read_bandwidth + perf->write_bandwidth =3D=3D 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 t=
o its
> > @@ -713,7 +767,7 @@ 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.wri=
te_bandwidth) /
> >               (perf->read_bandwidth + perf->write_bandwidth);
> > -     mutex_unlock(&memory_tier_lock);
> > +     mutex_unlock(&mt_perf_lock);
> >
> >       return 0;
> >  }
> > @@ -836,6 +890,14 @@ 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 nu=
ma nodes.
> > +                      * These will be initialized when HMAT informatio=
n is
>
> HMAT is platform specific, we should avoid to mention it in general code
> if possible.
>

Will fix! Thanks,


> > +                      * available.
> > +                      */
> > +                     continue;
> > +
> >               memtier =3D set_node_memory_tier(node);
> >               if (IS_ERR(memtier))
> >                       /*
>
> --
> Best Regards,
> Huang, Ying


--=20
Best regards,
Ho-Ren (Jack) Chuang
=E8=8E=8A=E8=B3=80=E4=BB=BB