Message-ID: <CAKPbEqoz8eqH30f_q9v2CiR+3D2xN9K+=NEZ1DcQ0OaR1KMTXA@mail.gmail.com>
Date: Tue, 5 Mar 2024 19:55:07 -0800
From: "Ho-Ren (Jack) Chuang" <horenchuang@...edance.com>
To: "Huang, Ying" <ying.huang@...el.com>
Cc: Gregory Price <gourry.memverge@...il.com>, aneesh.kumar@...ux.ibm.com, mhocko@...e.com, 
	tj@...nel.org, john@...alactic.com, Eishan Mirakhur <emirakhur@...ron.com>, 
	Vinicius Tavares Petrucci <vtavarespetr@...ron.com>, Ravis OpenSrc <Ravis.OpenSrc@...ron.com>, 
	Alistair Popple <apopple@...dia.com>, "Rafael J. Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>, 
	Andrew Morton <akpm@...ux-foundation.org>, Dave Jiang <dave.jiang@...el.com>, 
	Dan Williams <dan.j.williams@...el.com>, Jonathan Cameron <Jonathan.Cameron@...wei.com>, 
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org, 
	"Ho-Ren (Jack) Chuang" <horenc@...edu>, "Ho-Ren (Jack) Chuang" <horenchuang@...il.com>, linux-cxl@...r.kernel.org, 
	qemu-devel@...gnu.org
Subject: Re: [External] Re: [PATCH v1 1/1] memory tier: acpi/hmat: create
 CPUless memory tiers after obtaining HMAT info

On Tue, Mar 5, 2024 at 6:27 PM Huang, Ying <ying.huang@...el.com> wrote:
>
> "Ho-Ren (Jack) Chuang" <horenchuang@...edance.com> writes:
>
> > On Sun, Mar 3, 2024 at 6:42 PM Huang, Ying <ying.huang@...el.com> wrote:
> >>
> >> Hi, Jack,
> >>
> >> "Ho-Ren (Jack) Chuang" <horenchuang@...edance.com> writes:
> >>
> >> > * Introduce `mt_init_with_hmat()`
> >> > We defer memory tier initialization for those CPUless NUMA nodes
> >> > until acquiring HMAT info. `mt_init_with_hmat()` is introduced to
> >> > post-create CPUless memory tiers after obtaining HMAT info.
> >> > It iterates through each CPUless memory node, creating memory tiers if
> >> > necessary. Finally, it calculates demotion tables again at the end.
> >> >
> >> > * Introduce `hmat_find_alloc_memory_type()`
> >> > Find or allocate a memory type in the `hmat_memory_types` list.
> >> >
> >> > * Make `set_node_memory_tier()` more generic
> >> > This function can also be used for setting other memory types for a node.
> >> > To do so, a new argument is added to specify a memory type.
> >> >
> >> > * Handle cases where there is no HMAT when creating memory tiers
> >> > If no HMAT is specified, it falls back to using `default_dram_type`.
> >> >
> >> > * Change adist calculation code to use another new lock, mt_perf_lock.
> >> > 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.
> >>
> >> The patch description is used to described why we need the change, and
> >> how we do that, but not what we do.  People can tell what is done from
> >> the code itself.
> >>
> >
> > Got it. Thanks. Will rewrite it after the code is finalized.
> >
> >> > Signed-off-by: Ho-Ren (Jack) Chuang <horenchuang@...edance.com>
> >> > Signed-off-by: Hao Xiang <hao.xiang@...edance.com>
> >> > ---
> >> >  drivers/acpi/numa/hmat.c     |  3 ++
> >> >  include/linux/memory-tiers.h |  6 +++
> >> >  mm/memory-tiers.c            | 76 ++++++++++++++++++++++++++++++++----
> >> >  3 files changed, 77 insertions(+), 8 deletions(-)
> >> >
> >> > diff --git a/drivers/acpi/numa/hmat.c b/drivers/acpi/numa/hmat.c
> >> > index d6b85f0f6082..9f57338b3cb5 100644
> >> > --- a/drivers/acpi/numa/hmat.c
> >> > +++ b/drivers/acpi/numa/hmat.c
> >> > @@ -1038,6 +1038,9 @@ 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 */
> >> > +     mt_init_with_hmat();
> >> > +
> >> >       return 0;
> >> >  out_put:
> >> >       hmat_free_structures();
> >> > diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
> >> > index 69e781900082..2f845e90c033 100644
> >> > --- a/include/linux/memory-tiers.h
> >> > +++ b/include/linux/memory-tiers.h
> >> > @@ -48,6 +48,7 @@ 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);
> >> > +void mt_init_with_hmat(void);
> >>
> >> HMAT isn't universally available.  It's a driver in fact.  So, don't put
> >> driver specific code in general code.
> >>
> >
> > Please see below regarding "move code to hmat.c"
> >
> >> >  #ifdef CONFIG_MIGRATION
> >> >  int next_demotion_node(int node);
> >> >  void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *targets);
> >> > @@ -136,5 +137,10 @@ static inline int mt_perf_to_adistance(struct access_coordinate *perf, int *adis
> >> >  {
> >> >       return -EIO;
> >> >  }
> >> > +
> >> > +static inline void mt_init_with_hmat(void)
> >> > +{
> >> > +
> >> > +}
> >> >  #endif       /* CONFIG_NUMA */
> >> >  #endif  /* _LINUX_MEMORY_TIERS_H */
> >> > diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
> >> > index 0537664620e5..7a0a579b3deb 100644
> >> > --- a/mm/memory-tiers.c
> >> > +++ b/mm/memory-tiers.c
> >> > @@ -35,7 +35,9 @@ struct node_memory_type_map {
> >> >  };
> >> >
> >> >  static DEFINE_MUTEX(memory_tier_lock);
> >> > +static DEFINE_MUTEX(mt_perf_lock);
> >> >  static LIST_HEAD(memory_tiers);
> >> > +static LIST_HEAD(hmat_memory_types);
> >> >  static struct node_memory_type_map node_memory_types[MAX_NUMNODES];
> >> >  struct memory_dev_type *default_dram_type;
> >> >
> >> > @@ -502,7 +504,7 @@ static inline void __init_node_memory_type(int node, struct memory_dev_type *mem
> >> >       }
> >> >  }
> >> >
> >> > -static struct memory_tier *set_node_memory_tier(int node)
> >> > +static struct memory_tier *set_node_memory_tier(int node, struct memory_dev_type *new_memtype)
> >>
> >> No. memory_dev_type are passed to the function via node_memory_types[node].memtype.
> >>
> >
> > Got it. Will mimic the way kmem.c does. Thanks.
> >
> >> >  {
> >> >       struct memory_tier *memtier;
> >> >       struct memory_dev_type *memtype;
> >> > @@ -514,7 +516,7 @@ 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);
> >> > +     __init_node_memory_type(node, new_memtype);
> >> >
> >> >       memtype = node_memory_types[node].memtype;
> >> >       node_set(node, memtype->nodes);
> >> > @@ -623,6 +625,56 @@ void clear_node_memory_type(int node, struct memory_dev_type *memtype)
> >> >  }
> >> >  EXPORT_SYMBOL_GPL(clear_node_memory_type);
> >> >
> >> > +static struct memory_dev_type *hmat_find_alloc_memory_type(int adist)
> >>
> >> Similar function existed in drivers/dax/kmem.c.  Please abstract them
> >> and move them here.
> >>
> >
> > Got it. Will try. Thanks.
> >
> >> > +{
> >> > +     bool found = false;
> >> > +     struct memory_dev_type *mtype;
> >> > +
> >> > +     list_for_each_entry(mtype, &hmat_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, &hmat_memory_types);
> >> > +     }
> >> > +     return mtype;
> >> > +}
> >> > +
> >> > +static void mt_create_with_hmat(int node)
> >> > +{
> >> > +     struct memory_dev_type *mtype = NULL;
> >> > +     int adist = MEMTIER_ADISTANCE_DRAM;
> >> > +
> >> > +     mt_calc_adistance(node, &adist);
> >> > +     if (adist != MEMTIER_ADISTANCE_DRAM) {
> >> > +             mtype = hmat_find_alloc_memory_type(adist);
> >> > +             if (IS_ERR(mtype))
> >> > +                     pr_err("%s() failed to allocate a tier\n", __func__);
> >> > +     } else {
> >> > +             mtype = default_dram_type;
> >> > +     }
> >> > +
> >> > +     set_node_memory_tier(node, mtype);
> >> > +}
> >> > +
> >> > +void mt_init_with_hmat(void)
> >> > +{
> >> > +     int nid;
> >> > +
> >> > +     mutex_lock(&memory_tier_lock);
> >> > +     for_each_node_state(nid, N_MEMORY)
> >> > +             if (!node_state(nid, N_CPU))
> >> > +                     mt_create_with_hmat(nid);
> >> > +
> >> > +     establish_demotion_targets();
> >> > +     mutex_unlock(&memory_tier_lock);
> >> > +}
> >> > +EXPORT_SYMBOL_GPL(mt_init_with_hmat);
> >> > +
> >>
> >> I guess that we can put most hmat related code above in hmat.c.
> >>
> >
> > To put the heat-related code to hmat.c I will need to export some
> > static functions in memory-tiers.c, like set_node_memory_tier() and
> > establish_demotion_targets(). Is that ok?
>
> Think about this again.  In fact, although there are "_hmat" in the name
> of the above functions, the code has nothing to do with hmat.  So, we
> should rename these functions, but don't need to move them to hmat.c.
> And, to set memory_tier for CPUless node on system without HMAT.  We
> should call mt_init_with_hmat() with late_initcall().  Where HMAT
> information is expected to be available on system with HMAT.  On system
> without HMAT, default_dram_type will be used.
>

Sounds good and thank you! I'm working on v2 according to the feedback.

> >> >  static void dump_hmem_attrs(struct access_coordinate *coord, const char *prefix)
> >> >  {
> >> >       pr_info(
> >> > @@ -636,7 +688,7 @@ int mt_set_default_dram_perf(int nid, struct access_coordinate *perf,
> >> >  {
> >> >       int rc = 0;
> >> >
> >> > -     mutex_lock(&memory_tier_lock);
> >> > +     mutex_lock(&mt_perf_lock);
> >> >       if (default_dram_perf_error) {
> >> >               rc = -EIO;
> >> >               goto out;
> >> > @@ -684,7 +736,7 @@ 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 +752,7 @@ 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 +765,7 @@ 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;
> >> >  }
> >> > @@ -797,7 +849,7 @@ static int __meminit memtier_hotplug_callback(struct notifier_block *self,
> >> >               break;
> >> >       case MEM_ONLINE:
> >> >               mutex_lock(&memory_tier_lock);
> >> > -             memtier = set_node_memory_tier(arg->status_change_nid);
> >> > +             memtier = set_node_memory_tier(arg->status_change_nid, default_dram_type);
> >> >               if (!IS_ERR(memtier))
> >> >                       establish_demotion_targets();
> >> >               mutex_unlock(&memory_tier_lock);
> >> > @@ -836,7 +888,15 @@ static int __init memory_tier_init(void)
> >> >        * types assigned.
> >> >        */
> >> >       for_each_node_state(node, N_MEMORY) {
> >> > -             memtier = set_node_memory_tier(node);
> >> > +             if (!node_state(node, N_CPU))
> >> > +                     /*
> >> > +                      * Defer memory tier initialization on CPUless numa nodes.
> >> > +                      * These will be initialized when HMAT information is
> >> > +                      * available.
> >> > +                      */
> >> > +                     continue;
> >> > +
> >> > +             memtier = set_node_memory_tier(node, default_dram_type);
> >>
> >> On system with HMAT, how to fall back CPU-less node to
> >> default_dram_type?  I found your description, but I don't find it in code.
> >>
> > I assume you meant without HMAT, if so,
> > because if no HMAT, adist will not be updated in mt_calc_adistance():
>
> Sorry, typo.  On system with HMAT, mt_init_with_hmat() will not be
> called.  I have a solution in above comment.
>
> --
> Best Regards,
> Huang, Ying
>
> > + int adist = MEMTIER_ADISTANCE_DRAM;
> > +
> > + mt_calc_adistance(node, &adist);
> > + if (adist != MEMTIER_ADISTANCE_DRAM) {
> > …
> > + } else {
> > + mtype = default_dram_type;
> > + }
> > +
> > + set_node_memory_tier(node, mtype);
> >
> >> >               if (IS_ERR(memtier))
> >> >                       /*
> >> >                        * Continue with memtiers we are able to setup
> >>
> >> --
> >> Best Regards,
> >> Huang, Ying



-- 
Best regards,
Ho-Ren (Jack) Chuang
莊賀任

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