[PATCH v2] man2: add MPOL_WEIGHTED_INTERLEAVE documentation

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---
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@xxxxxxxxxxxx/

Which was upstreamed to 6.9 here:
https://lore.kernel.org/linux-mm/20240313200532.34e4cff216acd3db8def4637@xxxxxxxxxxxxxxxxxxxx/

To: alx@xxxxxxxxxx
Cc: linux-man@xxxxxxxxxxxxxxx
Cc: gregory.price@xxxxxxxxxxxx
Cc: ying.huang@xxxxxxxxx
Signed-off-by: Svetly Todorov <svetly.todorov@xxxxxxxxxxxx>

Changes in v2:
- make flag documentation implementation-agnostic
- Link to v1: https://lore.kernel.org/r/20240314-weighted_interleave-v1-1-ce85d64db0d4@xxxxxxxxxxxx
---
 man2/get_mempolicy.2 |  8 ++++++--
 man2/mbind.2         | 12 ++++++++++++
 man2/set_mempolicy.2 | 12 ++++++++++++
 3 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/man2/get_mempolicy.2 b/man2/get_mempolicy.2
index 5248f04ba..03550331d 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 ,
+.BR 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 .
+.BR MPOL_INTERLEAVE
+or
+.BR MPOL_WEIGHTED_INTERLEAVE .
 Or,
 .I flags
 specified
diff --git a/man2/mbind.2 b/man2/mbind.2
index b0e961f9c..4673f077e 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 +244,17 @@ 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 /sys/kernel/mm/mempolicy/weighted_interleave.
+For example, if bits 0, 2, and 5 are raised in
+.IR nodemask ,
+and the contents of /sys/kernel/mm/mempolicy/weighted_interleave/node0,
+/sys/.../node2, and /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..e2f5e5bf8 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 +200,17 @@ 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 /sys/kernel/mm/mempolicy/weighted_interleave.
+For example, if bits 0, 2, and 5 are raised in
+.IR nodemask ,
+and the contents of /sys/kernel/mm/mempolicy/weighted_interleave/node0,
+/sys/.../node2, and /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@xxxxxxxxxxxx>





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