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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
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@@ -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