Re: [PATCH] man2/set_mempolicy.2: Add mode flag MPOL_F_NUMA_BALANCING

["Huang, Ying" <ying.huang@intel.com>]

Huang Ying <ying.huang@intel.com> writes:

> In Linux kernel 5.12, a new mode flag MPOL_F_NUMA_BALANCING is added
> to set_mempolicy() to optimize the page placement among the NUMA nodes
> with the NUMA balancing mechanism even if the memory of the
> applications are bound with MPOL_BIND.  This patch update the man page
> for the new mode flag.
>
> Related kernel commits:
> bda420b985054a3badafef23807c4b4fa38a3dff

Hi, Colomar,

Do you have time to take a look at this patch?  It has been reviewed in
the following thread,

https://lore.kernel.org/lkml/20210120061235.148637-3-ying.huang@intel.com/

Now the corresponding kernel change has been merged by upstream kernel.
Do you have further comments?

Best Regards,
Huang, Ying

> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
> Cc: "Alejandro Colomar" <alx.manpages@gmail.com>
> Cc: "Michael Kerrisk" <mtk.manpages@gmail.com>
> ---
>  man2/set_mempolicy.2 | 34 ++++++++++++++++++++++++++++------
>  1 file changed, 28 insertions(+), 6 deletions(-)
>
> diff --git a/man2/set_mempolicy.2 b/man2/set_mempolicy.2
> index 6e695fb13..cd543667f 100644
> --- a/man2/set_mempolicy.2
> +++ b/man2/set_mempolicy.2
> @@ -98,6 +98,28 @@ The supported
>  .I "mode flags"
>  are:
>  .TP
> +.BR MPOL_F_NUMA_BALANCING " (since Linux 5.12)"
> +When
> +.I mode
> +is
> +.BR MPOL_BIND ,
> +enable the kernel NUMA balancing for the task if it is supported by
> +the kernel.
> +If the flag isn't supported by the kernel, or is used with
> +.I mode
> +other than
> +.BR MPOL_BIND ,
> +\-1 is returned and
> +.I errno
> +is set to
> +.BR EINVAL .
> +.TP
> +.BR MPOL_F_RELATIVE_NODES " (since Linux 2.6.26)"
> +A nonempty
> +.I nodemask
> +specifies node IDs that are relative to the set of
> +node IDs allowed by the process's current cpuset.
> +.TP
>  .BR MPOL_F_STATIC_NODES " (since Linux 2.6.26)"
>  A nonempty
>  .I nodemask
> @@ -107,12 +129,6 @@ Linux will not remap the
>  when the process moves to a different cpuset context,
>  nor when the set of nodes allowed by the process's
>  current cpuset context changes.
> -.TP
> -.BR MPOL_F_RELATIVE_NODES " (since Linux 2.6.26)"
> -A nonempty
> -.I nodemask
> -specifies node IDs that are relative to the set of
> -node IDs allowed by the process's current cpuset.
>  .PP
>  .I nodemask
>  points to a bit mask of node IDs that contains up to
> @@ -293,6 +309,12 @@ argument specified both
>  .B MPOL_F_STATIC_NODES
>  and
>  .BR MPOL_F_RELATIVE_NODES .
> +Or, the
> +.B MPOL_F_NUMA_BALANCING
> +isn't supported by the kernel, or is used with
> +.I mode
> +other than
> +.BR MPOL_BIND .
>  .TP
>  .B ENOMEM
>  Insufficient kernel memory was available.