[PATCH 1/1] mm: change per-VMA lock statistics to be disabled by default

[PATCH 1/1] mm: change per-VMA lock statistics to be disabled by default

[Suren Baghdasaryan]

Change CONFIG_PER_VMA_LOCK_STATS to be disabled by default, as most
users don't need it. Add configuration help to clarify its usage.

Fixes: 52f238653e45 ("mm: introduce per-VMA lock statistics")
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
 mm/Kconfig.debug | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
index 6dae63b46368..a925415b4d10 100644
--- a/mm/Kconfig.debug
+++ b/mm/Kconfig.debug
@@ -274,6 +274,12 @@ config DEBUG_KMEMLEAK_AUTO_SCAN
 config PER_VMA_LOCK_STATS
 	bool "Statistics for per-vma locks"
 	depends on PER_VMA_LOCK
-	default y
 	help
-	  Statistics for per-vma locks.
+	  Say Y here to enable success, retry and failure counters of page
+	  faults handled under protection of per-vma locks. When enabled, the
+	  counters are exposed in /proc/vmstat. This information is useful for
+	  kernel developers to evaluate effectiveness of per-vma locks and to
+	  identify pathological cases. Counting these events introduces a small
+	  overhead in the page fault path.
+
+	  If in doubt, say N.
-- 
2.40.1.495.gc816e09b53d-goog

Re: [PATCH 1/1] mm: change per-VMA lock statistics to be disabled by default

[Lorenzo Stoakes]

On Fri, Apr 28, 2023 at 10:35:33AM -0700, Suren Baghdasaryan wrote:
> Change CONFIG_PER_VMA_LOCK_STATS to be disabled by default, as most
> users don't need it. Add configuration help to clarify its usage.
>
> Fixes: 52f238653e45 ("mm: introduce per-VMA lock statistics")
> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> ---
>  mm/Kconfig.debug | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
> index 6dae63b46368..a925415b4d10 100644
> --- a/mm/Kconfig.debug
> +++ b/mm/Kconfig.debug
> @@ -274,6 +274,12 @@ config DEBUG_KMEMLEAK_AUTO_SCAN
>  config PER_VMA_LOCK_STATS
>  	bool "Statistics for per-vma locks"
>  	depends on PER_VMA_LOCK
> -	default y
>  	help
> -	  Statistics for per-vma locks.
> +	  Say Y here to enable success, retry and failure counters of page
> +	  faults handled under protection of per-vma locks. When enabled, the
> +	  counters are exposed in /proc/vmstat. This information is useful for
> +	  kernel developers to evaluate effectiveness of per-vma locks and to
> +	  identify pathological cases. Counting these events introduces a small
> +	  overhead in the page fault path.
> +
> +	  If in doubt, say N.
> --
> 2.40.1.495.gc816e09b53d-goog
>

Reviewed-by: Lorenzo Stoakes <lstoakes@gmail.com>

Re: [PATCH 1/1] mm: change per-VMA lock statistics to be disabled by default

[Vlastimil Babka]

On 4/28/23 19:35, Suren Baghdasaryan wrote:
> Change CONFIG_PER_VMA_LOCK_STATS to be disabled by default, as most
> users don't need it. Add configuration help to clarify its usage.
> 
> Fixes: 52f238653e45 ("mm: introduce per-VMA lock statistics")
> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Suren Baghdasaryan <surenb@google.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
>  mm/Kconfig.debug | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
> index 6dae63b46368..a925415b4d10 100644
> --- a/mm/Kconfig.debug
> +++ b/mm/Kconfig.debug
> @@ -274,6 +274,12 @@ config DEBUG_KMEMLEAK_AUTO_SCAN
>  config PER_VMA_LOCK_STATS
>  	bool "Statistics for per-vma locks"
>  	depends on PER_VMA_LOCK
> -	default y
>  	help
> -	  Statistics for per-vma locks.
> +	  Say Y here to enable success, retry and failure counters of page
> +	  faults handled under protection of per-vma locks. When enabled, the
> +	  counters are exposed in /proc/vmstat. This information is useful for
> +	  kernel developers to evaluate effectiveness of per-vma locks and to
> +	  identify pathological cases. Counting these events introduces a small
> +	  overhead in the page fault path.
> +
> +	  If in doubt, say N.

Re: [PATCH 1/1] mm: change per-VMA lock statistics to be disabled by default

[David Hildenbrand]

On 28.04.23 19:35, Suren Baghdasaryan wrote:
> Change CONFIG_PER_VMA_LOCK_STATS to be disabled by default, as most
> users don't need it. Add configuration help to clarify its usage.
> 
> Fixes: 52f238653e45 ("mm: introduce per-VMA lock statistics")
> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> ---
>   mm/Kconfig.debug | 10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
> index 6dae63b46368..a925415b4d10 100644
> --- a/mm/Kconfig.debug
> +++ b/mm/Kconfig.debug
> @@ -274,6 +274,12 @@ config DEBUG_KMEMLEAK_AUTO_SCAN
>   config PER_VMA_LOCK_STATS
>   	bool "Statistics for per-vma locks"
>   	depends on PER_VMA_LOCK
> -	default y
>   	help
> -	  Statistics for per-vma locks.
> +	  Say Y here to enable success, retry and failure counters of page
> +	  faults handled under protection of per-vma locks. When enabled, the
> +	  counters are exposed in /proc/vmstat. This information is useful for
> +	  kernel developers to evaluate effectiveness of per-vma locks and to
> +	  identify pathological cases. Counting these events introduces a small
> +	  overhead in the page fault path.
> +
> +	  If in doubt, say N.

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb