x86, generic: CPA add statistics about state of direct mapping v4

Add information about the mapping state of the direct mapping to
/proc/meminfo. I chose /proc/meminfo because that is where all the other
memory statistics are too and it is a generally useful metric even
outside debugging situations. A lot of split kernel pages means the
kernel will run slower.

This way we can see how many large pages are really used for it and how
many are split.

Useful for general insight into the kernel.

v2: Add hotplug locking to 64bit to plug a very obscure theoretical race.
    32bit doesn't need it because it doesn't support hotadd for lowmem.
    Fix some typos
v3: Rename dpages_cnt
    Add CONFIG ifdef for count update as requested by tglx
    Expand description
v4: Fix stupid bugs added in v3
    Move update_page_count to pageattr.c

Signed-off-by: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 35 insertions, 0 deletions

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 60bcb5b6a37e..668205bca15e 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -34,6 +34,19 @@ struct cpa_data {
         unsigned        force_split : 1;
 };
 
+static unsigned long direct_pages_count[PG_LEVEL_NUM];
+
+void __meminit update_page_count(int level, unsigned long pages)
+{
+#ifdef CONFIG_PROC_FS
+        unsigned long flags;
+        /* Protect against CPA */
+        spin_lock_irqsave(&pgd_lock, flags);
+        direct_pages_count[level] += pages;
+        spin_unlock_irqrestore(&pgd_lock, flags);
+#endif
+}
+
 #ifdef CONFIG_X86_64
 
 static inline unsigned long highmap_start_pfn(void)
@@ -500,6 +513,12 @@ static int split_large_page(pte_t *kpte, unsigned long address)
         for (i = 0; i < PTRS_PER_PTE; i++, pfn += pfninc)
                 set_pte(&pbase[i], pfn_pte(pfn, ref_prot));
 
+        if (address >= (unsigned long)__va(0) &&
+                address < (unsigned long)__va(max_pfn_mapped << PAGE_SHIFT)) {
+                direct_pages_count[level]--;
+                direct_pages_count[level - 1] += PTRS_PER_PTE;
+        }
+
         /*
          * Install the new, split up pagetable. Important details here:
          *
@@ -1029,6 +1048,22 @@ bool kernel_page_present(struct page *page)
 
 #endif /* CONFIG_DEBUG_PAGEALLOC */
 
+#ifdef CONFIG_PROC_FS
+int arch_report_meminfo(char *page)
+{
+        int n;
+        n = sprintf(page, "DirectMap4k:  %8lu\n"
+                          "DirectMap2M:  %8lu\n",
+                        direct_pages_count[PG_LEVEL_4K],
+                        direct_pages_count[PG_LEVEL_2M]);
+#ifdef CONFIG_X86_64
+        n += sprintf(page + n, "DirectMap1G:  %8lu\n",
+                        direct_pages_count[PG_LEVEL_1G]);
+#endif
+        return n;
+}
+#endif
+
 /*
  * The testcases use internal knowledge of the implementation that shouldn't
  * be exposed to the rest of the kernel. Include these directly here.