[PATCH v4 2/2] mm: show number of vmalloc pages in /proc/meminfo

[Roman Gushchin]

Vmalloc() is getting more and more used these days (kernel stacks,
bpf and percpu allocator are new top users), and the total %
of memory consumed by vmalloc() can be pretty significant
and changes dynamically.

/proc/meminfo is the best place to display this information:
its top goal is to show top consumers of the memory.

Since the VmallocUsed field in /proc/meminfo is not in use
for quite a long time (it has been defined to 0 by the
commit a5ad88ce8c7f ("mm: get rid of 'vmalloc_info' from
/proc/meminfo")), let's reuse it for showing the actual
physical memory consumption of vmalloc().

Signed-off-by: Roman Gushchin <g...@fb.com>
Acked-by: Johannes Weiner <han...@cmpxchg.org>
Acked-by: Vlastimil Babka <vba...@suse.cz>
---
 fs/proc/meminfo.c       |  2 +-
 include/linux/vmalloc.h |  2 ++
 mm/vmalloc.c            | 10 ++++++++++
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
index 568d90e17c17..465ea0153b2a 100644
--- a/fs/proc/meminfo.c
+++ b/fs/proc/meminfo.c
@@ -120,7 +120,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
        show_val_kb(m, "Committed_AS:   ", committed);
        seq_printf(m, "VmallocTotal:   %8lu kB\n",
                   (unsigned long)VMALLOC_TOTAL >> 10);
-       show_val_kb(m, "VmallocUsed:    ", 0ul);
+       show_val_kb(m, "VmallocUsed:    ", vmalloc_nr_pages());
        show_val_kb(m, "VmallocChunk:   ", 0ul);
        show_val_kb(m, "Percpu:         ", pcpu_nr_pages());
 
diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index ad483378fdd1..316efa31c8b8 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -67,10 +67,12 @@ extern void vm_unmap_aliases(void);
 
 #ifdef CONFIG_MMU
 extern void __init vmalloc_init(void);
+extern unsigned long vmalloc_nr_pages(void);
 #else
 static inline void vmalloc_init(void)
 {
 }
+static inline unsigned long vmalloc_nr_pages(void) { return 0; }
 #endif
 
 extern void *vmalloc(unsigned long size);
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 8ad8e8464e55..69a5673c4cd3 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -397,6 +397,13 @@ static void purge_vmap_area_lazy(void);
 static BLOCKING_NOTIFIER_HEAD(vmap_notify_list);
 static unsigned long lazy_max_pages(void);
 
+static atomic_long_t nr_vmalloc_pages;
+
+unsigned long vmalloc_nr_pages(void)
+{
+       return atomic_long_read(&nr_vmalloc_pages);
+}
+
 static struct vmap_area *__find_vmap_area(unsigned long addr)
 {
        struct rb_node *n = vmap_area_root.rb_node;
@@ -2141,6 +2148,7 @@ static void __vunmap(const void *addr, int 
deallocate_pages)
                        BUG_ON(!page);
                        __free_pages(page, 0);
                }
+               atomic_long_sub(area->nr_pages, &nr_vmalloc_pages);
 
                kvfree(area->pages);
        }
@@ -2317,12 +2325,14 @@ static void *__vmalloc_area_node(struct vm_struct 
*area, gfp_t gfp_mask,
                if (unlikely(!page)) {
                        /* Successfully allocated i pages, free them in 
__vunmap() */
                        area->nr_pages = i;
+                       atomic_long_add(area->nr_pages, &nr_vmalloc_pages);
                        goto fail;
                }
                area->pages[i] = page;
                if (gfpflags_allow_blocking(gfp_mask|highmem_mask))
                        cond_resched();
        }
+       atomic_long_add(area->nr_pages, &nr_vmalloc_pages);
 
        if (map_vm_area(area, prot, pages))
                goto fail;
-- 
2.20.1