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s390/pgtable: add mapping statistics
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Add statistics that show how memory is mapped within the kernel
identity mapping. This is more or less the same like git
commit ce0c0e5 ("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>
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Heiko Carstens authored and Martin Schwidefsky committed Jun 13, 2016
1 parent bab247f commit 37cd944
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19 changes: 19 additions & 0 deletions arch/s390/include/asm/pgtable.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,7 @@
#include <linux/mm_types.h>
#include <linux/page-flags.h>
#include <linux/radix-tree.h>
#include <linux/atomic.h>
#include <asm/bug.h>
#include <asm/page.h>

Expand All @@ -37,6 +38,24 @@ extern void vmem_map_init(void);
pmd_t *vmem_pmd_alloc(void);
pte_t *vmem_pte_alloc(void);

enum {
PG_DIRECT_MAP_4K = 0,
PG_DIRECT_MAP_1M,
PG_DIRECT_MAP_2G,
PG_DIRECT_MAP_MAX
};

extern atomic_long_t direct_pages_count[PG_DIRECT_MAP_MAX];

static inline void update_page_count(int level, long count)
{
if (IS_ENABLED(CONFIG_PROC_FS))
atomic_long_add(count, &direct_pages_count[level]);
}

struct seq_file;
void arch_report_meminfo(struct seq_file *m);

/*
* The S390 doesn't have any external MMU info: the kernel page
* tables contain all the necessary information.
Expand Down
18 changes: 18 additions & 0 deletions arch/s390/mm/pageattr.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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)
{
Expand Down Expand Up @@ -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;
}

Expand Down Expand Up @@ -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;
}

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16 changes: 16 additions & 0 deletions arch/s390/mm/vmem.c
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Original file line number Diff line number Diff line change
Expand Up @@ -80,6 +80,7 @@ pte_t __ref *vmem_pte_alloc(void)
*/
static int vmem_add_mem(unsigned long start, unsigned long size)
{
unsigned long pages4k, pages1m, pages2g;
unsigned long end = start + size;
unsigned long address = start;
pgd_t *pg_dir;
Expand All @@ -88,6 +89,7 @@ static int vmem_add_mem(unsigned long start, unsigned long size)
pte_t *pt_dir;
int ret = -ENOMEM;

pages4k = pages1m = pages2g = 0;
while (address < end) {
pg_dir = pgd_offset_k(address);
if (pgd_none(*pg_dir)) {
Expand All @@ -102,6 +104,7 @@ static int vmem_add_mem(unsigned long start, unsigned long size)
!debug_pagealloc_enabled()) {
pud_val(*pu_dir) = address | pgprot_val(REGION3_KERNEL);
address += PUD_SIZE;
pages2g++;
continue;
}
if (pud_none(*pu_dir)) {
Expand All @@ -116,6 +119,7 @@ static int vmem_add_mem(unsigned long start, unsigned long size)
!debug_pagealloc_enabled()) {
pmd_val(*pm_dir) = address | pgprot_val(SEGMENT_KERNEL);
address += PMD_SIZE;
pages1m++;
continue;
}
if (pmd_none(*pm_dir)) {
Expand All @@ -128,9 +132,13 @@ static int vmem_add_mem(unsigned long start, unsigned long size)
pt_dir = pte_offset_kernel(pm_dir, address);
pte_val(*pt_dir) = address | pgprot_val(PAGE_KERNEL);
address += PAGE_SIZE;
pages4k++;
}
ret = 0;
out:
update_page_count(PG_DIRECT_MAP_4K, pages4k);
update_page_count(PG_DIRECT_MAP_1M, pages1m);
update_page_count(PG_DIRECT_MAP_2G, pages2g);
return ret;
}

Expand All @@ -140,13 +148,15 @@ static int vmem_add_mem(unsigned long start, unsigned long size)
*/
static void vmem_remove_range(unsigned long start, unsigned long size)
{
unsigned long pages4k, pages1m, pages2g;
unsigned long end = start + size;
unsigned long address = start;
pgd_t *pg_dir;
pud_t *pu_dir;
pmd_t *pm_dir;
pte_t *pt_dir;

pages4k = pages1m = pages2g = 0;
while (address < end) {
pg_dir = pgd_offset_k(address);
if (pgd_none(*pg_dir)) {
Expand All @@ -161,6 +171,7 @@ static void vmem_remove_range(unsigned long start, unsigned long size)
if (pud_large(*pu_dir)) {
pud_clear(pu_dir);
address += PUD_SIZE;
pages2g++;
continue;
}
pm_dir = pmd_offset(pu_dir, address);
Expand All @@ -171,13 +182,18 @@ static void vmem_remove_range(unsigned long start, unsigned long size)
if (pmd_large(*pm_dir)) {
pmd_clear(pm_dir);
address += PMD_SIZE;
pages1m++;
continue;
}
pt_dir = pte_offset_kernel(pm_dir, address);
pte_clear(&init_mm, address, pt_dir);
address += PAGE_SIZE;
pages4k++;
}
flush_tlb_kernel_range(start, end);
update_page_count(PG_DIRECT_MAP_4K, -pages4k);
update_page_count(PG_DIRECT_MAP_1M, -pages1m);
update_page_count(PG_DIRECT_MAP_2G, -pages2g);
}

/*
Expand Down

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