Commit 839195352d82 ("mm/shuffle: remove dynamic reconfiguration")
removed the dynamic reconfiguration capabilities from the shuffle page
allocator. This means that, now, we don't have any perspective of an
"autodetection of memory-side-cache" that triggers the enablement of the
shuffle page allocator.
Therefore, let the documentation reflect that the only way to enable
the shuffle page allocator is by setting `page_alloc.shuffle=1`.
Signed-off-by: Maíra Canal <[email protected]>
---
Documentation/admin-guide/kernel-parameters.txt | 10 ++++------
mm/Kconfig | 7 +++----
2 files changed, 7 insertions(+), 10 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 902ecd92a29f..924bb8ddd8a8 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4170,13 +4170,11 @@
page_alloc.shuffle=
[KNL] Boolean flag to control whether the page allocator
- should randomize its free lists. The randomization may
- be automatically enabled if the kernel detects it is
- running on a platform with a direct-mapped memory-side
- cache, and this parameter can be used to
- override/disable that behavior. The state of the flag
- can be read from sysfs at:
+ should randomize its free lists. This parameter can be
+ used to enable/disable page randomization. The state of
+ the flag can be read from sysfs at:
/sys/module/page_alloc/parameters/shuffle.
+ This parameter is only available if CONFIG_SHUFFLE_PAGE_ALLOCATOR=y.
page_owner= [KNL,EARLY] Boot-time page_owner enabling option.
Storage of the information about who allocated
diff --git a/mm/Kconfig b/mm/Kconfig
index b1448aa81e15..f30a18a0e37d 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -333,10 +333,9 @@ config SHUFFLE_PAGE_ALLOCATOR
While the randomization improves cache utilization it may
negatively impact workloads on platforms without a cache. For
- this reason, by default, the randomization is enabled only
- after runtime detection of a direct-mapped memory-side-cache.
- Otherwise, the randomization may be force enabled with the
- 'page_alloc.shuffle' kernel command line parameter.
+ this reason, by default, the randomization is not enabled even
+ if SHUFFLE_PAGE_ALLOCATOR=y. The randomization may be force enabled
+ with the 'page_alloc.shuffle' kernel command line parameter.
Say Y if unsure.
--
2.44.0
On 22.04.24 16:18, Maíra Canal wrote:
> Commit 839195352d82 ("mm/shuffle: remove dynamic reconfiguration")
> removed the dynamic reconfiguration capabilities from the shuffle page
> allocator. This means that, now, we don't have any perspective of an
> "autodetection of memory-side-cache" that triggers the enablement of the
> shuffle page allocator.
IIRC (it's been a while), we never had that autodetection upstream; we
only had the code in place that would never get called. 839195352d82
removed that (dead) code.
>
> Therefore, let the documentation reflect that the only way to enable
> the shuffle page allocator is by setting `page_alloc.shuffle=1`.
>
> Signed-off-by: Maíra Canal <[email protected]>
> ---
> Documentation/admin-guide/kernel-parameters.txt | 10 ++++------
> mm/Kconfig | 7 +++----
> 2 files changed, 7 insertions(+), 10 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 902ecd92a29f..924bb8ddd8a8 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -4170,13 +4170,11 @@
>
> page_alloc.shuffle=
> [KNL] Boolean flag to control whether the page allocator
> - should randomize its free lists. The randomization may
> - be automatically enabled if the kernel detects it is
> - running on a platform with a direct-mapped memory-side
> - cache, and this parameter can be used to
> - override/disable that behavior. The state of the flag
> - can be read from sysfs at:
> + should randomize its free lists. This parameter can be
> + used to enable/disable page randomization. The state of
> + the flag can be read from sysfs at:
> /sys/module/page_alloc/parameters/shuffle.
> + This parameter is only available if CONFIG_SHUFFLE_PAGE_ALLOCATOR=y.
>
> page_owner= [KNL,EARLY] Boot-time page_owner enabling option.
> Storage of the information about who allocated
> diff --git a/mm/Kconfig b/mm/Kconfig
> index b1448aa81e15..f30a18a0e37d 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -333,10 +333,9 @@ config SHUFFLE_PAGE_ALLOCATOR
>
> While the randomization improves cache utilization it may
> negatively impact workloads on platforms without a cache. For
> - this reason, by default, the randomization is enabled only
> - after runtime detection of a direct-mapped memory-side-cache.
> - Otherwise, the randomization may be force enabled with the
> - 'page_alloc.shuffle' kernel command line parameter.
> + this reason, by default, the randomization is not enabled even
> + if SHUFFLE_PAGE_ALLOCATOR=y. The randomization may be force enabled
> + with the 'page_alloc.shuffle' kernel command line parameter.
>
> Say Y if unsure.
>
Reviewed-by: David Hildenbrand <[email protected]>
--
Cheers,
David / dhildenb
Maíra Canal <[email protected]> writes:
> Commit 839195352d82 ("mm/shuffle: remove dynamic reconfiguration")
> removed the dynamic reconfiguration capabilities from the shuffle page
> allocator. This means that, now, we don't have any perspective of an
> "autodetection of memory-side-cache" that triggers the enablement of the
> shuffle page allocator.
>
> Therefore, let the documentation reflect that the only way to enable
> the shuffle page allocator is by setting `page_alloc.shuffle=1`.
>
> Signed-off-by: Maíra Canal <[email protected]>
> ---
> Documentation/admin-guide/kernel-parameters.txt | 10 ++++------
> mm/Kconfig | 7 +++----
> 2 files changed, 7 insertions(+), 10 deletions(-)
Applied, thanks.
jon