Yafang Shao <laoar.shao@xxxxxxxxx> writes:
> The document on MPOL_F_NUMA_BALANCING was missed in the initial commit
> The MPOL_F_NUMA_BALANCING document was inadvertently omitted from the
> initial commit bda420b98505 ("numa balancing: migrate on fault among
> multiple bound nodes")
>
> Let's ensure its inclusion.
>
> Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> Cc: "Huang, Ying" <ying.huang@xxxxxxxxx>
LGTM, Thanks!
Reviewed-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
> ---
> .../admin-guide/mm/numa_memory_policy.rst | 27 +++++++++++++++++++
> 1 file changed, 27 insertions(+)
>
> diff --git a/Documentation/admin-guide/mm/numa_memory_policy.rst b/Documentation/admin-guide/mm/numa_memory_policy.rst
> index eca38fa81e0f..19071b71979c 100644
> --- a/Documentation/admin-guide/mm/numa_memory_policy.rst
> +++ b/Documentation/admin-guide/mm/numa_memory_policy.rst
> @@ -332,6 +332,33 @@ MPOL_F_RELATIVE_NODES
> MPOL_PREFERRED policies that were created with an empty nodemask
> (local allocation).
>
> +MPOL_F_NUMA_BALANCING (since Linux 5.12)
> + When operating in MPOL_BIND mode, enables NUMA balancing for tasks,
> + contingent upon kernel support. This feature optimizes page
> + placement within the confines of the specified memory binding
> + policy. The addition of the MPOL_F_NUMA_BALANCING flag augments the
> + control mechanism for NUMA balancing:
> +
> + - The sysctl knob numa_balancing governs global activation or
> + deactivation of NUMA balancing.
> +
> + - Even if sysctl numa_balancing is enabled, NUMA balancing remains
> + disabled by default for memory areas or applications utilizing
> + explicit memory policies.
> +
> + - The MPOL_F_NUMA_BALANCING flag facilitates NUMA balancing
> + activation for applications employing explicit memory policies
> + (MPOL_BIND).
> +
> + This flags enables various optimizations for page placement through
> + NUMA balancing. For instance, when an application's memory is bound
> + to multiple nodes (MPOL_BIND), the hint page fault handler attempts
> + to migrate accessed pages to reduce cross-node access if the
> + accessing node aligns with the policy nodemask.
> +
> + If the flag isn't supported by the kernel, or is used with mode
> + other than MPOL_BIND, -1 is returned and errno is set to EINVAL.
> +
> Memory Policy Reference Counting
> ================================
--
Best Regards,
Huang, Ying
