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x86/mm/cpa: Add large page preservation statistics

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The large page preservation mechanism is just magic and provides no
information at all. Add optional statistic output in debugfs so the magic can
be evaluated. Defaults is off.

Output:

 1G pages checked:                    2
 1G pages sameprot:                   0
 1G pages preserved:                  0
 2M pages checked:                  540
 2M pages sameprot:                 466
 2M pages preserved:                 47
 4K pages checked:               800770
 4K pages set-checked:             7668

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Bin Yang <bin.yang@intel.com>
Cc: Mark Gross <mark.gross@intel.com>
Link: https://lkml.kernel.org/r/20180917143546.160867778@linutronix.de
This commit is contained in:
Thomas Gleixner 2018-09-17 16:29:12 +02:00
parent 4046460b86
commit 5c280cf608
2 changed files with 105 additions and 2 deletions
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8
arch/x86/Kconfig
View File

@ -1491,6 +1491,14 @@ config X86_DIRECT_GBPAGES
supports them), so don't confuse the user by printing
that we have them enabled.
config X86_CPA_STATISTICS
bool "Enable statistic for Change Page Attribute"
depends on DEBUG_FS
---help---
Expose statistics about the Change Page Attribute mechanims, which
helps to determine the effectivness of preserving large and huge
page mappings when mapping protections are changed.
config ARCH_HAS_MEM_ENCRYPT
def_bool y

99
arch/x86/mm/pageattr.c
View File

@ -101,6 +101,95 @@ void arch_report_meminfo(struct seq_file *m)
static inline void split_page_count(int level) { }
#endif
#ifdef CONFIG_X86_CPA_STATISTICS
static unsigned long cpa_1g_checked;
static unsigned long cpa_1g_sameprot;
static unsigned long cpa_1g_preserved;
static unsigned long cpa_2m_checked;
static unsigned long cpa_2m_sameprot;
static unsigned long cpa_2m_preserved;
static unsigned long cpa_4k_checked;
static unsigned long cpa_4k_install;
static inline void cpa_inc_1g_checked(void)
{
cpa_1g_checked++;
}
static inline void cpa_inc_2m_checked(void)
{
cpa_2m_checked++;
}
static inline void cpa_inc_4k_checked(void)
{
cpa_4k_checked++;
}
static inline void cpa_inc_4k_install(void)
{
cpa_4k_install++;
}
static inline void cpa_inc_lp_sameprot(int level)
{
if (level == PG_LEVEL_1G)
cpa_1g_sameprot++;
else
cpa_2m_sameprot++;
}
static inline void cpa_inc_lp_preserved(int level)
{
if (level == PG_LEVEL_1G)
cpa_1g_preserved++;
else
cpa_2m_preserved++;
}
static int cpastats_show(struct seq_file *m, void *p)
{
seq_printf(m, "1G pages checked: %16lu\n", cpa_1g_checked);
seq_printf(m, "1G pages sameprot: %16lu\n", cpa_1g_sameprot);
seq_printf(m, "1G pages preserved: %16lu\n", cpa_1g_preserved);
seq_printf(m, "2M pages checked: %16lu\n", cpa_2m_checked);
seq_printf(m, "2M pages sameprot: %16lu\n", cpa_2m_sameprot);
seq_printf(m, "2M pages preserved: %16lu\n", cpa_2m_preserved);
seq_printf(m, "4K pages checked: %16lu\n", cpa_4k_checked);
seq_printf(m, "4K pages set-checked: %16lu\n", cpa_4k_install);
return 0;
}
static int cpastats_open(struct inode *inode, struct file *file)
{
return single_open(file, cpastats_show, NULL);
}
static const struct file_operations cpastats_fops = {
.open = cpastats_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
static int __init cpa_stats_init(void)
{
debugfs_create_file("cpa_stats", S_IRUSR, arch_debugfs_dir, NULL,
&cpastats_fops);
return 0;
}
late_initcall(cpa_stats_init);
#else
static inline void cpa_inc_1g_checked(void) { }
static inline void cpa_inc_2m_checked(void) { }
static inline void cpa_inc_4k_checked(void) { }
static inline void cpa_inc_4k_install(void) { }
static inline void cpa_inc_lp_sameprot(int level) { }
static inline void cpa_inc_lp_preserved(int level) { }
#endif
static inline int
within(unsigned long addr, unsigned long start, unsigned long end)
{
@ -664,10 +753,12 @@ static int __should_split_large_page(pte_t *kpte, unsigned long address,
case PG_LEVEL_2M:
old_prot = pmd_pgprot(*(pmd_t *)kpte);
old_pfn = pmd_pfn(*(pmd_t *)kpte);
cpa_inc_2m_checked();
break;
case PG_LEVEL_1G:
old_prot = pud_pgprot(*(pud_t *)kpte);
old_pfn = pud_pfn(*(pud_t *)kpte);
cpa_inc_1g_checked();
break;
default:
return -EINVAL;
@ -732,14 +823,16 @@ static int __should_split_large_page(pte_t *kpte, unsigned long address,
for (i = 0, addr = lpaddr; i < numpages; i++, addr += PAGE_SIZE, pfn++) {
pgprot_t chk_prot = static_protections(req_prot, addr, pfn, 1,
CPA_DETECT);
cpa_inc_4k_checked();
if (pgprot_val(chk_prot) != pgprot_val(new_prot))
return 1;
}
/* If there are no changes, return. */
if (pgprot_val(new_prot) == pgprot_val(old_prot))
if (pgprot_val(new_prot) == pgprot_val(old_prot)) {
cpa_inc_lp_sameprot(level);
return 0;
}
/*
* Verify that the address is aligned and the number of pages
@ -752,6 +845,7 @@ static int __should_split_large_page(pte_t *kpte, unsigned long address,
new_pte = pfn_pte(old_pfn, new_prot);
__set_pmd_pte(kpte, address, new_pte);
cpa->flags |= CPA_FLUSHTLB;
cpa_inc_lp_preserved(level);
return 0;
}
@ -1341,6 +1435,7 @@ static int __change_page_attr(struct cpa_data *cpa, int primary)
pgprot_val(new_prot) &= ~pgprot_val(cpa->mask_clr);
pgprot_val(new_prot) |= pgprot_val(cpa->mask_set);
cpa_inc_4k_install();
new_prot = static_protections(new_prot, address, pfn, 1,
CPA_PROTECT);