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Subject[1/3] x86: Update DEBUG_TLBFLUSH options description.
CONFIG_DEBUG_TLBFLUSH was added in 'commit 3df3212f9722 ("x86/tlb: add
tlb_flushall_shift knob into debugfs")' to support tlb_flushall_shift
knob. The knob was removed in 'commit e9f4e0a9fe27 ("x86/mm: Rip out
complicated, out-of-date, buggy TLB flushing")'. However, the debug
option was never removed from Kconfig. It was reused in commit
'9824cf9753ec ("mm: vmstats: tlb flush counters")' but the commit text was
never updated accordingly.

Update the Kconfig option description as per its current usage.

Signed-off-by: Atish Patra <>
arch/x86/Kconfig.debug | 15 +++------------
1 file changed, 3 insertions(+), 12 deletions(-)

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 15d0fbe27872..c1a48d4ffebb 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -125,21 +125,12 @@ config DOUBLEFAULT

- bool "Set upper limit of TLB entries to flush one-by-one"
+ bool "Save tlb flush statstics to vmstat"
depends on DEBUG_KERNEL

- X86-only for now.
- This option allows the user to tune the amount of TLB entries the
- kernel flushes one-by-one instead of doing a full TLB flush. In
- certain situations, the former is cheaper. This is controlled by the
- tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it
- to -1, the code flushes the whole TLB unconditionally. Otherwise,
- for positive values of it, the kernel will use single TLB entry
- invalidating instructions according to the following formula:
- flush_entries <= active_tlb_entries / 2^tlb_flushall_shift
+ Add tlbflush statstics to vmstat. It is really helpful understand tlbflush
+ performance and behavior. It should be enabled only for debugging purpose.

If in doubt, say "N".

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