s390/pgtable: add mapping statistics

Add statistics that show how memory is mapped within the kernel
identity mapping. This is more or less the same like git
commit ce0c0e50f94e ("x86, generic: CPA add statistics about state
of direct mapping v4") for x86.

I also intentionally copied the lower case "k" within DirectMap4k vs
the upper case "M" and "G" within the two other lines. Let's have
consistent inconsistencies across architectures.

The output of /proc/meminfo now contains these additional lines:

DirectMap4k:        2048 kB
DirectMap1M:     3991552 kB
DirectMap2G:     4194304 kB

The implementation on s390 is lockless unlike the x86 version, since I
assume changes to the kernel mapping are a very rare event. Therefore
it really doesn't matter if these statistics could potentially be
inconsistent if read while kernel pages tables are being changed.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/arch/s390/mm/pageattr.c b/arch/s390/mm/pageattr.c
index 91e5e29c1f5c..ba124d9c96ba 100644
--- a/arch/s390/mm/pageattr.c
+++ b/arch/s390/mm/pageattr.c
@@ -40,6 +40,20 @@ void __storage_key_init_range(unsigned long start, unsigned long end)
 }
 #endif
 
+#ifdef CONFIG_PROC_FS
+atomic_long_t direct_pages_count[PG_DIRECT_MAP_MAX];
+
+void arch_report_meminfo(struct seq_file *m)
+{
+	seq_printf(m, "DirectMap4k:    %8lu kB\n",
+		   atomic_long_read(&direct_pages_count[PG_DIRECT_MAP_4K]) << 2);
+	seq_printf(m, "DirectMap1M:    %8lu kB\n",
+		   atomic_long_read(&direct_pages_count[PG_DIRECT_MAP_1M]) << 10);
+	seq_printf(m, "DirectMap2G:    %8lu kB\n",
+		   atomic_long_read(&direct_pages_count[PG_DIRECT_MAP_2G]) << 21);
+}
+#endif /* CONFIG_PROC_FS */
+
 static void pgt_set(unsigned long *old, unsigned long new, unsigned long addr,
 		    unsigned long dtt)
 {
@@ -114,6 +128,8 @@ static int split_pmd_page(pmd_t *pmdp, unsigned long addr)
 	}
 	pmd_val(new) = __pa(pt_dir) | _SEGMENT_ENTRY;
 	pgt_set((unsigned long *)pmdp, pmd_val(new), addr, CRDTE_DTT_SEGMENT);
+	update_page_count(PG_DIRECT_MAP_4K, PTRS_PER_PTE);
+	update_page_count(PG_DIRECT_MAP_1M, -1);
 	return 0;
 }
 
@@ -181,6 +197,8 @@ static int split_pud_page(pud_t *pudp, unsigned long addr)
 	}
 	pud_val(new) = __pa(pm_dir) | _REGION3_ENTRY;
 	pgt_set((unsigned long *)pudp, pud_val(new), addr, CRDTE_DTT_REGION3);
+	update_page_count(PG_DIRECT_MAP_1M, PTRS_PER_PMD);
+	update_page_count(PG_DIRECT_MAP_2G, -1);
 	return 0;
 }