linux-kernel - Re: [PATCH v2] mm/demotion: Expose memory tier details via sysfs

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Message-Id: <20220829140030.692cfd4dfbf7f9a8b282c951@linux-foundation.org>
Date:   Mon, 29 Aug 2022 14:00:30 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>
Cc:     linux-mm@...ck.org, Wei Xu <weixugc@...gle.com>,
        Huang Ying <ying.huang@...el.com>,
        Yang Shi <shy828301@...il.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Tim C Chen <tim.c.chen@...el.com>,
        Michal Hocko <mhocko@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Hesham Almatary <hesham.almatary@...wei.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Alistair Popple <apopple@...dia.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Johannes Weiner <hannes@...xchg.org>, jvgediya.oss@...il.com,
        Bharata B Rao <bharata@....com>
Subject: Re: [PATCH v2] mm/demotion: Expose memory tier details via sysfs

On Mon, 29 Aug 2022 11:37:45 +0530 "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com> wrote:

> This patch adds /sys/devices/virtual/memory_tiering/ where all memory tier
> related details can be found. All allocated memory tiers will be listed
> there as /sys/devices/virtual/memory_tiering/memory_tierN/
> 
> The nodes which are part of a specific memory tier can be listed via
> /sys/devices/virtual/memory_tiering/memory_tierN/nodes
> 
> The abstract distance range value of a specific memory tier can be listed via
> /sys/devices/virtual/memory_tiering/memory_tierN/abstract_distance
> 
> A directory hierarchy looks like
> :/sys/devices/virtual/memory_tiering$ tree memory_tier4/
> memory_tier4/
> ├── abstract_distance
> ├── nodes
> ├── subsystem -> ../../../../bus/memory_tiering
> └── uevent
> 
> All toptier nodes are listed via
> /sys/devices/virtual/memory_tiering/toptier_nodes
> 
> :/sys/devices/virtual/memory_tiering$ cat toptier_nodes
> 0,2
> :/sys/devices/virtual/memory_tiering$ cat memory_tier4/nodes
> 0,2
> :/sys/devices/virtual/memory_tiering$ cat memory_tier4/abstract_distance
> 512 - 639
> 
> ...
>
> --- a/mm/memory-tiers.c
> +++ b/mm/memory-tiers.c
> @@ -19,6 +19,7 @@ struct memory_tier {
>  	 * adistance_start .. adistance_start + MEMTIER_CHUNK_SIZE
>  	 */
>  	int adistance_start;
> +	struct device dev;
>  	/* All the nodes that are part of all the lower memory tiers. */
>  	nodemask_t lower_tier_mask;
>  };
> @@ -36,6 +37,13 @@ static DEFINE_MUTEX(memory_tier_lock);
>  static LIST_HEAD(memory_tiers);
>  static struct node_memory_type_map node_memory_types[MAX_NUMNODES];
>  static struct memory_dev_type *default_dram_type;
> +
> +#define to_memory_tier(device) container_of(device, struct memory_tier, dev)

Please, only use a macro when a C function cannot be used.

--- a/mm/memory-tiers.c~mm-demotion-expose-memory-tier-details-via-sysfs-fix
+++ a/mm/memory-tiers.c
@@ -38,7 +38,11 @@ static LIST_HEAD(memory_tiers);
 static struct node_memory_type_map node_memory_types[MAX_NUMNODES];
 static struct memory_dev_type *default_dram_type;
 
-#define to_memory_tier(device) container_of(device, struct memory_tier, dev)
+static inline struct memory_tier *to_memory_tier(struct device *device)
+{
+	return container_of(device, struct memory_tier, dev);
+}
+
 static struct bus_type memory_tier_subsys = {
 	.name = "memory_tiering",
 	.dev_name = "memory_tier",

If only so it checks the type of `device'.