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complicated, out-of-date, buggy TLB flushing")'.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.
Take this opprtunity to make this kconfig option a common option as it
touches the common vmstat code. Introduce another arch specific config
HAVE_ARCH_DEBUG_TLBFLUSH that can be selected to enable this config.
Signed-off-by: Atish Patra <[email protected]>
---
arch/x86/Kconfig | 1 +
arch/x86/Kconfig.debug | 19 -------------------
mm/Kconfig.debug | 13 +++++++++++++
3 files changed, 14 insertions(+), 19 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 62fc3fda1a05..4c59f59e9491 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -132,6 +132,7 @@ config X86
select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
select HAVE_ARCH_VMAP_STACK if X86_64
select HAVE_ARCH_WITHIN_STACK_FRAMES
+ select HAVE_ARCH_DEBUG_TLBFLUSH if DEBUG_KERNEL
select HAVE_CMPXCHG_DOUBLE
select HAVE_CMPXCHG_LOCAL
select HAVE_CONTEXT_TRACKING if X86_64
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 15d0fbe27872..0c8f9931e901 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -124,25 +124,6 @@ config DOUBLEFAULT
option saves about 4k and might cause you much additional grey
hair.
-config DEBUG_TLBFLUSH
- bool "Set upper limit of TLB entries to flush one-by-one"
- depends on DEBUG_KERNEL
- ---help---
-
- 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
-
- If in doubt, say "N".
-
config IOMMU_DEBUG
bool "Enable IOMMU debugging"
depends on GART_IOMMU && DEBUG_KERNEL
diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
index e3df921208c0..760c3fda8b57 100644
--- a/mm/Kconfig.debug
+++ b/mm/Kconfig.debug
@@ -111,3 +111,16 @@ config DEBUG_RODATA_TEST
depends on STRICT_KERNEL_RWX
---help---
This option enables a testcase for the setting rodata read-only.
+
+config HAVE_ARCH_DEBUG_TLBFLUSH
+ bool
+ depends on DEBUG_KERNEL
+
+config DEBUG_TLBFLUSH
+ bool "Save tlb flush statstics to vmstat"
+ depends on HAVE_ARCH_DEBUG_TLBFLUSH
+ help
+
+ Add tlbflush statstics to vmstat. It is really helpful understand tlbflush
+ performance and behavior. It should be enabled only for debugging purpose
+ by individual architectures explicitly by selecting HAVE_ARCH_DEBUG_TLBFLUSH.
--
2.21.0
* Atish Patra <[email protected]> wrote:
> 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.
Please, when you mention several commits, put them into new lines to make
it readable, i.e.:
3df3212f9722 ("x86/tlb: add tlb_flushall_shift knob into debugfs")
etc.
> Update the Kconfig option description as per its current usage.
>
> Take this opprtunity to make this kconfig option a common option as it
> touches the common vmstat code. Introduce another arch specific config
> HAVE_ARCH_DEBUG_TLBFLUSH that can be selected to enable this config.
"opprtunity"?
> +config HAVE_ARCH_DEBUG_TLBFLUSH
> + bool
> + depends on DEBUG_KERNEL
> +
> +config DEBUG_TLBFLUSH
> + bool "Save tlb flush statstics to vmstat"
> + depends on HAVE_ARCH_DEBUG_TLBFLUSH
> + help
> +
> + Add tlbflush statstics to vmstat. It is really helpful understand tlbflush
> + performance and behavior. It should be enabled only for debugging purpose
> + by individual architectures explicitly by selecting HAVE_ARCH_DEBUG_TLBFLUSH.
"statstics"??
Please put a spell checker into your workflow or read what you are
writing ...
Thanks,
Ingo
On 4/29/19 1:06 PM, Ingo Molnar wrote:
>
> * Atish Patra <[email protected]> wrote:
>
>> 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.
>
> Please, when you mention several commits, put them into new lines to make
> it readable, i.e.:
>
> 3df3212f9722 ("x86/tlb: add tlb_flushall_shift knob into debugfs")
>
> etc.
>
Done.
>> Update the Kconfig option description as per its current usage.
>>
>> Take this opprtunity to make this kconfig option a common option as it
>> touches the common vmstat code. Introduce another arch specific config
>> HAVE_ARCH_DEBUG_TLBFLUSH that can be selected to enable this config.
>
> "opprtunity"?
>
>> +config HAVE_ARCH_DEBUG_TLBFLUSH
>> + bool
>> + depends on DEBUG_KERNEL
>> +
>> +config DEBUG_TLBFLUSH
>> + bool "Save tlb flush statstics to vmstat"
>> + depends on HAVE_ARCH_DEBUG_TLBFLUSH
>> + help
>> +
>> + Add tlbflush statstics to vmstat. It is really helpful understand tlbflush
>> + performance and behavior. It should be enabled only for debugging purpose
>> + by individual architectures explicitly by selecting HAVE_ARCH_DEBUG_TLBFLUSH.
>
> "statstics"??
>
> Please put a spell checker into your workflow or read what you are
> writing ...
>
Apologies for the typos. Fixed them.
Regards,
Atish
> Thanks,
>
> Ingo
>