Re: [PATCH v4] man2: add MPOL_WEIGHTED_INTERLEAVE documentation

Alejandro Colomar
2024-03-16T21:06:55Z

[-- Attachment #1: Type: text/plain, Size: 5006 bytes --]

Hi Svetly,

On Sat, Mar 16, 2024 at 12:50:47PM -0700, Svetly Todorov wrote:
>
>
> ---
> Adding documentation for the new MPOL_WEIGHTED_INTERLEAVE mode in the same
> manpages that mention MPOL_INTERLEAVE; namely, mbind(2), set_mempolicy(2),
> and get_mempolicy(2).
>
> Descriptions were based on the changes introduced in this patch:
> https://lore.kernel.org/all/20240202170238.90004-4-gregory.price@memverge.com/
>
> Which was upstreamed to 6.9 here:
> https://lore.kernel.org/linux-mm/20240313200532.34e4cff216acd3db8def4637@linux-foundation.org/
>
> To: alx@kernel.org
> Cc: linux-man@vger.kernel.org
> Cc: gregory.price@memverge.com
> Cc: ying.huang@intel.com
> Signed-off-by: Svetly Todorov <svetly.todorov@memverge.com>
>
> Changes in v4:
> - BR -> B in get_mempolicy
> - use roman for ellipses; format using \|
> - Link to v3: https://lore.kernel.org/r/20240315-weighted_interleave-v3-1-416a1ab01524@memverge.com
>
> Changes in v3:
> - italicize paths
> - Link to v2: https://lore.kernel.org/r/20240315-weighted_interleave-v2-1-b742a48750b0@memverge.com
>
> Changes in v2:
> - make flag documentation implementation-agnostic
> - Link to v1: https://lore.kernel.org/r/20240314-weighted_interleave-v1-1-ce85d64db0d4@memverge.com
> ---
> man2/get_mempolicy.2 | 8 ++++++--
> man2/mbind.2 | 17 +++++++++++++++++
> man2/set_mempolicy.2 | 17 +++++++++++++++++
> 3 files changed, 40 insertions(+), 2 deletions(-)
>
> diff --git a/man2/get_mempolicy.2 b/man2/get_mempolicy.2
> index 5248f04ba..a81b84a00 100644
> --- a/man2/get_mempolicy.2
> +++ b/man2/get_mempolicy.2
> @@ -137,7 +137,9 @@ specifies
> but not
> .BR MPOL_F_ADDR ,
> and the thread's current policy is
> -.BR MPOL_INTERLEAVE ,
> +.B MPOL_INTERLEAVE
> +or
> +.BR MPOL_WEIGHTED_INTERLEAVE ,
> then
> .BR get_mempolicy ()
> will return in the location pointed to by a non-NULL
> @@ -206,7 +208,9 @@ specified
> but not
> .B MPOL_F_ADDR
> and the current thread policy is not
> -.BR MPOL_INTERLEAVE .
> +.B MPOL_INTERLEAVE
> +or
> +.BR MPOL_WEIGHTED_INTERLEAVE .
> Or,
> .I flags
> specified
> diff --git a/man2/mbind.2 b/man2/mbind.2
> index b0e961f9c..cd4e6f4a4 100644
> --- a/man2/mbind.2
> +++ b/man2/mbind.2
> @@ -105,6 +105,7 @@ argument must specify one of
> .BR MPOL_DEFAULT ,
> .BR MPOL_BIND ,
> .BR MPOL_INTERLEAVE ,
> +.BR MPOL_WEIGHTED_INTERLEAVE ,
> .BR MPOL_PREFERRED ,
> or
> .B MPOL_LOCAL
> @@ -243,6 +244,22 @@ at least 1\ MB or bigger with a fairly uniform access pattern.
> Accesses to a single page of the area will still be limited to
> the memory bandwidth of a single node.
> .TP
> +.B MPOL_WEIGHTED_INTERLEAVE

We should document the kernel version that added this.
Please look for other (since ...) in the same page.

Have a lovely night!
Alex

> +This mode interleaves page allocations across the nodes specified in
> +.I nodemask
> +according to the weights in
> +.IR /sys/kernel/mm/mempolicy/weighted_interleave .
> +For example, if bits 0, 2, and 5 are raised in
> +.IR nodemask ,
> +and the contents of
> +.IR /sys/kernel/mm/mempolicy/weighted_interleave/node0 ,
> +.IR /sys/ .\|.\|. /node2 ,
> +and
> +.IR /sys/ .\|.\|. /node5
> +are 4, 7, and 9, respectively,
> +then pages in this region will be allocated on nodes 0, 2, and 5
> +in a 4:7:9 ratio.
> +.TP
> .B MPOL_PREFERRED
> This mode sets the preferred node for allocation.
> The kernel will try to allocate pages from this
> diff --git a/man2/set_mempolicy.2 b/man2/set_mempolicy.2
> index fc3ad9df8..f9837d918 100644
> --- a/man2/set_mempolicy.2
> +++ b/man2/set_mempolicy.2
> @@ -63,6 +63,7 @@ argument must specify one of
> .BR MPOL_DEFAULT ,
> .BR MPOL_BIND ,
> .BR MPOL_INTERLEAVE ,
> +.BR MPOL_WEIGHTED_INTERLEAVE ,
> .BR MPOL_PREFERRED ,
> or
> .B MPOL_LOCAL
> @@ -199,6 +200,22 @@ the memory bandwidth of a single node.
> .\" To be effective the memory area should be fairly large,
> .\" at least 1 MB or bigger.
> .TP
> +.B MPOL_WEIGHTED_INTERLEAVE
> +This mode interleaves page allocations across the nodes specified in
> +.I nodemask
> +according to the weights in
> +.IR /sys/kernel/mm/mempolicy/weighted_interleave .
> +For example, if bits 0, 2, and 5 are raised in
> +.IR nodemask ,
> +and the contents of
> +.IR /sys/kernel/mm/mempolicy/weighted_interleave/node0 ,
> +.IR /sys/ .\|.\|. /node2 ,
> +and
> +.IR /sys/ .\|.\|. /node5
> +are 4, 7, and 9, respectively,
> +then pages in this region will be allocated on nodes 0, 2, and 5
> +in a 4:7:9 ratio.
> +.TP
> .B MPOL_PREFERRED
> This mode sets the preferred node for allocation.
> The kernel will try to allocate pages from this node first
>
> ---
> base-commit: a4ea5f76215dcf1d8d017eb65ab12919ccf09f3f
> change-id: 20240313-weighted_interleave-e8141ed754f9
>
> Best regards,
> --
> Svetly Todorov <svetly.todorov@memverge.com>