Browsing a header file in the kernel source and saw the memory policy enum used
for mbind() and set_mempolicy() using an entry that I didn't recognize. I man 2'd
both system calls and didn't see an entry for MPOL_PREFERRED_MANY. The commit on
the enum entry:
Commit b27abaccf8e8 ("mm/mempolicy: added MPOL_PREFERRED_MANY for multiple
preferred nodes")
The commit message gives the rationale as to why the MPOL_PREFERRED_MANY mode
would be beneficial. Giving the ability to set the memory policy to target
different tiers of memory over different NUMA nodes.
Signed-off-by: Matthew Cassell <mcassell411@xxxxxxxxx>
---
man/man2/mbind.2 | 11 +++++++++++
man/man2/set_mempolicy.2 | 11 +++++++++++
2 files changed, 22 insertions(+)
diff --git a/man/man2/mbind.2 b/man/man2/mbind.2
index fd1aca4ad..a5a7f4bdc 100644
--- a/man/man2/mbind.2
+++ b/man/man2/mbind.2
@@ -107,6 +107,7 @@ argument must specify one of
.BR MPOL_INTERLEAVE ,
.BR MPOL_WEIGHTED_INTERLEAVE ,
.BR MPOL_PREFERRED ,
+.BR MPOL_PREFERRED_MANY ,
or
.B MPOL_LOCAL
(which are described in detail below).
@@ -277,6 +278,16 @@ and
arguments specify the empty set, then the memory is allocated on
the node of the CPU that triggered the allocation.
.TP
+.BR MPOL_PREFERRED_MANY " (since Linux 5.15)"
+.\" commit b27abaccf8e8b012f126da0c2a1ab32723ec8b9f
+This mode specifies a preference for nodes from which the kernel will
+try to allocate from. This differs from
+.BR MPOL_PREFERRED
+in that it accepts a set of nodes versus a single node. This policy
+is intended to benefit page allocations where specific memory types
+(i.e. non-volatile, high-bandwidth, or accelerator memory) are of
+greater importance than node location.
+.TP
.BR MPOL_LOCAL " (since Linux 3.8)"
.\" commit 479e2802d09f1e18a97262c4c6f8f17ae5884bd8
.\" commit f2a07f40dbc603c15f8b06e6ec7f768af67b424f
diff --git a/man/man2/set_mempolicy.2 b/man/man2/set_mempolicy.2
index 2d0b1da19..f4651ccd3 100644
--- a/man/man2/set_mempolicy.2
+++ b/man/man2/set_mempolicy.2
@@ -65,6 +65,7 @@ argument must specify one of
.BR MPOL_INTERLEAVE ,
.BR MPOL_WEIGHTED_INTERLEAVE ,
.BR MPOL_PREFERRED ,
+.BR MPOL_PREFERRED_MANY ,
or
.B MPOL_LOCAL
(which are described in detail below).
@@ -234,6 +235,16 @@ arguments specify the empty set, then the policy
specifies "local allocation"
(like the system default policy discussed above).
.TP
+.BR MPOL_PREFERRED_MANY " (since Linux 5.15)"
+.\" commit b27abaccf8e8b012f126da0c2a1ab32723ec8b9f
+This mode specifies a preference for nodes from which the kernel will
+try to allocate from. This differs from
+.BR MPOL_PREFERRED
+in that it accepts a set of nodes versus a single node. This policy
+is intended to benefit page allocations where specific memory types
+(i.e. non-volatile, high-bandwidth, or accelerator memory) are of
+greater importance than node location.
+.TP
.BR MPOL_LOCAL " (since Linux 3.8)"
.\" commit 479e2802d09f1e18a97262c4c6f8f17ae5884bd8
.\" commit f2a07f40dbc603c15f8b06e6ec7f768af67b424f
--
2.39.5 (Apple Git-154)
