2023-04-28 17:42:36

by Suren Baghdasaryan

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

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 <[email protected]>
Signed-off-by: Suren Baghdasaryan <[email protected]>
---
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

2023-04-28 17:47:47

by Lorenzo Stoakes

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

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 <[email protected]>
> Signed-off-by: Suren Baghdasaryan <[email protected]>
> ---
> 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 <[email protected]>

2023-05-02 10:05:39

by Vlastimil Babka

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

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 <[email protected]>
> Signed-off-by: Suren Baghdasaryan <[email protected]>

Acked-by: Vlastimil Babka <[email protected]>

> ---
> 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.

2023-05-02 11:31:14

by David Hildenbrand

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

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 <[email protected]>
> Signed-off-by: Suren Baghdasaryan <[email protected]>
> ---
> 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 <[email protected]>

--
Thanks,

David / dhildenb