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: linux.git b27abaccf8e8 (2021-09-02; "mm/mempolicy: add 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 various NUMA nodes. v0 -> v1 - changed text width from 80 to 72 characters - added Cc tag for commit author - improved source readability with semantic newlines - changed mbind() to refer to set_mempolicy() to avoid unnecessary duplication Cc: "Dave Hansen" <dave.hansen@xxxxxxxxxxxxxxx> Signed-off-by: Matthew Cassell <mcassell411@xxxxxxxxx> --- man/man2/mbind.2 | 6 ++++++ man/man2/set_mempolicy.2 | 14 ++++++++++++++ 2 files changed, 20 insertions(+) diff --git a/man/man2/mbind.2 b/man/man2/mbind.2 index fd1aca4ad..a060e1401 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 +278,11 @@ 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 +Specifies a set of nodes for allocation; see +.BR set_mempolicy(2) +.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..32c360f22 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 +235,19 @@ 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)
