[PATCH v1] docs: sysctl: timer_migration is for hrtimer only

[PATCH v1] docs: sysctl: timer_migration is for hrtimer only

[Costa Shulyupin]

Since commit b2cf7507e1864 ("timers: Always queue timers on the local
CPU") __mod_timer() no longer depends on timers_migration_enabled.  Only
high-resolution timer migration from isolated to housekeeping CPUs
depends on it.

Update and clarify the documentation accordingly.

Signed-off-by: Costa Shulyupin <costa.shul@redhat.com>
---
 Documentation/admin-guide/sysctl/kernel.rst | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index b6328cd0f43e..fb38d654846d 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -1609,8 +1609,10 @@ If a value outside of this range is written to ``threads-max`` an
 timer_migration
 ===============
 
-When set to a non-zero value, attempt to migrate timers away from idle cpus to
-allow them to remain in low power states longer.
+When set to a non-zero value, attempt to migrate high-resolution timers from
+nohz isolated (nohz_full) to housekeeping CPUs.
+See Documentation/admin-guide/cpu-isolation.rst
+and Documentation/admin-guide/kernel-parameters.rst.
 
 Default is set (1).
 
-- 
2.55.0

Re: [PATCH v1] docs: sysctl: timer_migration is for hrtimer only

[Bradley Morgan]

On 26 August 2026 14:29:19 BST, Costa Shulyupin <costa.shul@redhat.com>
wrote:

+ CC joel.granados@kernel.org (sysctl folk)

+CC  akpm@linux-foundation.org

>Since commit b2cf7507e1864 ("timers: Always queue timers on the local
>CPU") __mod_timer() no longer depends on timers_migration_enabled.  Only
>high-resolution timer migration from isolated to housekeeping CPUs
>depends on it.
>
>Update and clarify the documentation accordingly.
>
>Signed-off-by: Costa Shulyupin <costa.shul@redhat.com>
>---
> Documentation/admin-guide/sysctl/kernel.rst | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
>diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
>index b6328cd0f43e..fb38d654846d 100644
>--- a/Documentation/admin-guide/sysctl/kernel.rst
>+++ b/Documentation/admin-guide/sysctl/kernel.rst
>@@ -1609,8 +1609,10 @@ If a value outside of this range is written to ``threads-max`` an
> timer_migration
> ===============
> 
>-When set to a non-zero value, attempt to migrate timers away from idle cpus to
>-allow them to remain in low power states longer.
>+When set to a non-zero value, attempt to migrate high-resolution timers from
>+nohz isolated (nohz_full) to housekeeping CPUs.
>+See Documentation/admin-guide/cpu-isolation.rst
>+and Documentation/admin-guide/kernel-parameters.rst.
> 

Hmm, ok!

Reviewed-by: Bradley Morgan <brads@mainlining.org>


> Default is set (1).
> 
>

--- Thanks!
https://lore.kernel.org/all/EE579805-42F2-4C58-B752-F28779EEB717@grrlz.net/