linux-kernel - Re: [PATCH v9 1/2] memory tier: dax/kmem: introduce an abstract layer for finding, allocating, and putting memory types

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Date: Sun, 31 Mar 2024 12:08:57 -0700
From: SeongJae Park <sj@...nel.org>
To: "Ho-Ren (Jack) Chuang" <horenchuang@...edance.com>
Cc: SeongJae Park <sj@...nel.org>,
	"Huang, Ying" <ying.huang@...el.com>,
	"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>,
	"Srinivasulu Thanneeru" <sthanneeru@...ron.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Vishal Verma <vishal.l.verma@...el.com>,
	Dave Jiang <dave.jiang@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	nvdimm@...ts.linux.dev,
	linux-cxl@...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>,
	qemu-devel@...gnu.org
Subject: Re: [PATCH v9 1/2] memory tier: dax/kmem: introduce an abstract layer for finding, allocating, and putting memory types

Hi Ho-Ren,

On Fri, 29 Mar 2024 05:33:52 +0000 "Ho-Ren (Jack) Chuang" <horenchuang@...edance.com> wrote:

> Since different memory devices require finding, allocating, and putting
> memory types, these common steps are abstracted in this patch,
> enhancing the scalability and conciseness of the code.
> 
> Signed-off-by: Ho-Ren (Jack) Chuang <horenchuang@...edance.com>
> Reviewed-by: "Huang, Ying" <ying.huang@...el.com>
> ---
>  drivers/dax/kmem.c           | 20 ++------------------
>  include/linux/memory-tiers.h | 13 +++++++++++++
>  mm/memory-tiers.c            | 32 ++++++++++++++++++++++++++++++++
>  3 files changed, 47 insertions(+), 18 deletions(-)
> 
[...]
> diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
> index 69e781900082..a44c03c2ba3a 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 *mt_find_alloc_memory_type(int adist,
> +							struct list_head *memory_types);
> +void mt_put_memory_types(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 +139,15 @@ 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;
> +}
> +
> +void mt_put_memory_types(struct list_head *memory_types)
> +{
> +
> +}

I found latest mm-unstable tree is failing kunit as below, and 'git bisect'
says it happens from this patch.

    $ ./tools/testing/kunit/kunit.py run --build_dir ../kunit.out/
    [11:56:40] Configuring KUnit Kernel ...
    [11:56:40] Building KUnit Kernel ...
    Populating config with:
    $ make ARCH=um O=../kunit.out/ olddefconfig
    Building with:
    $ make ARCH=um O=../kunit.out/ --jobs=36
    ERROR:root:In file included from .../mm/memory.c:71:
    .../include/linux/memory-tiers.h:143:25: warning: no previous prototype for ‘mt_find_alloc_memory_type’ [-Wmissing-prototypes]
      143 | struct memory_dev_type *mt_find_alloc_memory_type(int adist, struct list_head *memory_types)
          |                         ^~~~~~~~~~~~~~~~~~~~~~~~~
    .../include/linux/memory-tiers.h:148:6: warning: no previous prototype for ‘mt_put_memory_types’ [-Wmissing-prototypes]
      148 | void mt_put_memory_types(struct list_head *memory_types)
          |      ^~~~~~~~~~~~~~~~~~~
    [...]

Maybe we should set these as 'static inline', like below?  I confirmed this
fixes the kunit error.  May I ask your opinion?

diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
index a44c03c2ba3a..ee6e53144156 100644
--- a/include/linux/memory-tiers.h
+++ b/include/linux/memory-tiers.h
@@ -140,12 +140,12 @@ 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)
+static inline struct memory_dev_type *mt_find_alloc_memory_type(int adist, struct list_head *memory_types)
 {
        return NULL;
 }

-void mt_put_memory_types(struct list_head *memory_types)
+static inline void mt_put_memory_types(struct list_head *memory_types)
 {

 }


Thanks,
SJ