Add NR_BALLOON_PAGES counter to track memory used by balloon drivers and
expose it through /proc/meminfo and other memory reporting interfaces.

Signed-off-by: Nico Pache <npache@redhat.com>
---
 fs/proc/meminfo.c      | 2 ++
 include/linux/mmzone.h | 1 +
 mm/show_mem.c          | 4 +++-
 mm/vmstat.c            | 1 +
 4 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
index 8ba9b1472390..83be312159c9 100644
--- a/fs/proc/meminfo.c
+++ b/fs/proc/meminfo.c
@@ -162,6 +162,8 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
 	show_val_kb(m, "Unaccepted:     ",
 		    global_zone_page_state(NR_UNACCEPTED));
 #endif
+	show_val_kb(m, "Balloon:        ",
+		    global_node_page_state(NR_BALLOON_PAGES));
 
 	hugetlb_report_meminfo(m);
 
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 9540b41894da..71d3ff19267a 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -223,6 +223,7 @@ enum node_stat_item {
 #ifdef CONFIG_HUGETLB_PAGE
 	NR_HUGETLB,
 #endif
+	NR_BALLOON_PAGES,
 	NR_VM_NODE_STAT_ITEMS
 };
 
diff --git a/mm/show_mem.c b/mm/show_mem.c
index 43afb56abbd3..6af13bcd2ab3 100644
--- a/mm/show_mem.c
+++ b/mm/show_mem.c
@@ -260,6 +260,7 @@ static void show_free_areas(unsigned int filter, nodemask_t *nodemask, int max_z
 			" pagetables:%lukB"
 			" sec_pagetables:%lukB"
 			" all_unreclaimable? %s"
+			" Balloon:%lukB"
 			"\n",
 			pgdat->node_id,
 			K(node_page_state(pgdat, NR_ACTIVE_ANON)),
@@ -285,7 +286,8 @@ static void show_free_areas(unsigned int filter, nodemask_t *nodemask, int max_z
 #endif
 			K(node_page_state(pgdat, NR_PAGETABLE)),
 			K(node_page_state(pgdat, NR_SECONDARY_PAGETABLE)),
-			str_yes_no(pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES));
+			str_yes_no(pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES),
+			K(node_page_state(pgdat, NR_BALLOON_PAGES)));
 	}
 
 	for_each_populated_zone(zone) {
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 16bfe1c694dd..d3b11891a942 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1276,6 +1276,7 @@ const char * const vmstat_text[] = {
 #ifdef CONFIG_HUGETLB_PAGE
 	"nr_hugetlb",
 #endif
+	"nr_balloon_pages",
 	/* system-wide enum vm_stat_item counters */
 	"nr_dirty_threshold",
 	"nr_dirty_background_threshold",
-- 
2.48.1

On Fri, 14 Mar 2025 15:37:54 -0600 Nico Pache <npache@redhat.com> wrote:

> Add NR_BALLOON_PAGES counter to track memory used by balloon drivers and
> expose it through /proc/meminfo and other memory reporting interfaces.
> 
> ...
>
> --- a/fs/proc/meminfo.c
> +++ b/fs/proc/meminfo.c
> @@ -162,6 +162,8 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
>  	show_val_kb(m, "Unaccepted:     ",
>  		    global_zone_page_state(NR_UNACCEPTED));
>  #endif
> +	show_val_kb(m, "Balloon:        ",
> +		    global_node_page_state(NR_BALLOON_PAGES));

Please update Documentation/filesystems/proc.rst for this.

On 3/14/25 7:06 PM, Andrew Morton wrote:
> On Fri, 14 Mar 2025 15:37:54 -0600 Nico Pache <npache@redhat.com> wrote:
> 
>> Add NR_BALLOON_PAGES counter to track memory used by balloon drivers and
>> expose it through /proc/meminfo and other memory reporting interfaces.
>>
>> ...
>>
>> --- a/fs/proc/meminfo.c
>> +++ b/fs/proc/meminfo.c
>> @@ -162,6 +162,8 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
>>  	show_val_kb(m, "Unaccepted:     ",
>>  		    global_zone_page_state(NR_UNACCEPTED));
>>  #endif
>> +	show_val_kb(m, "Balloon:        ",
>> +		    global_node_page_state(NR_BALLOON_PAGES));
> 
> Please update Documentation/filesystems/proc.rst for this.

@Andrew

Can you please squash the following?

From b1b379a32752e64c60b5e3b6365c93db8e1daf9f Mon Sep 17 00:00:00 2001
From: Nico Pache <npache@redhat.com>
Date: Mon, 17 Mar 2025 16:07:18 -0600
Subject: [PATCH] Documentation: document Balloon Meminfo entry

Add a Balloon entry to the Meminfo documention.

Signed-off-by: Nico Pache <npache@redhat.com>
---
 Documentation/filesystems/proc.rst | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
index 09f0aed5a08b..2868bb74f76e 100644
--- a/Documentation/filesystems/proc.rst
+++ b/Documentation/filesystems/proc.rst
@@ -1060,6 +1060,7 @@ Example output. You may not have all of these fields.
     FilePmdMapped:         0 kB
     CmaTotal:              0 kB
     CmaFree:               0 kB
+    Balloon:               0 kB
     HugePages_Total:       0
     HugePages_Free:        0
     HugePages_Rsvd:        0
@@ -1228,6 +1229,8 @@ CmaTotal
               Memory reserved for the Contiguous Memory Allocator (CMA)
 CmaFree
               Free remaining memory in the CMA reserves
+Balloon
+              Memory returned to Host by VM Balloon Drivers
 HugePages_Total, HugePages_Free, HugePages_Rsvd, HugePages_Surp, Hugepagesize,
Hugetlb
               See Documentation/admin-guide/mm/hugetlbpage.rst.
 DirectMap4k, DirectMap2M, DirectMap1G
-- 
2.48.1
>