[PATCH v4] man2: add MPOL_WEIGHTED_INTERLEAVE documentation

Svetly Todorov
2024-03-16T19:50:59Z

---
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
+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>