@@ -245,6 +245,14 @@ MPOL_INTERLEAVED
address range or file. During system boot up, the temporary
interleaved system default policy works in this mode.
+MPOL_PREFERRED_MANY
+ This mode specifies that the allocation should be attempted from the
+ nodemask specified in the policy. If that allocation fails, the kernel
+ will search other nodes, in order of increasing distance from the first
+ set bit in the nodemask based on information provided by the platform
+ firmware. It is similar to MPOL_PREFERRED with the main exception that
+ is is an error to have an empty nodemask.
+
NUMA memory policy supports the following optional mode flags:
MPOL_F_STATIC_NODES
@@ -253,10 +261,10 @@ MPOL_F_STATIC_NODES
nodes changes after the memory policy has been defined.
Without this flag, any time a mempolicy is rebound because of a
- change in the set of allowed nodes, the node (Preferred) or
- nodemask (Bind, Interleave) is remapped to the new set of
- allowed nodes. This may result in nodes being used that were
- previously undesired.
+ change in the set of allowed nodes, the preferred nodemask (Preferred
+ Many), preferred node (Preferred) or nodemask (Bind, Interleave) is
+ remapped to the new set of allowed nodes. This may result in nodes
+ being used that were previously undesired.
With this flag, if the user-specified nodes overlap with the
nodes allowed by the task's cpuset, then the memory policy is
@@ -16,13 +16,13 @@
*/
/* Policies */
-enum {
- MPOL_DEFAULT,
+enum { MPOL_DEFAULT,
MPOL_PREFERRED,
MPOL_BIND,
MPOL_INTERLEAVE,
MPOL_LOCAL,
- MPOL_MAX, /* always last member of enum */
+ MPOL_PREFERRED_MANY,
+ MPOL_MAX, /* always last member of enum */
};
/* Flags for set_mempolicy */
@@ -1115,7 +1115,7 @@ static struct page *dequeue_huge_page_vma(struct hstate *h,
gfp_mask = htlb_alloc_mask(h);
nid = huge_node(vma, address, gfp_mask, &mpol, &nodemask);
- if (mpol->mode != MPOL_BIND && nodemask) { /* AKA MPOL_PREFERRED_MANY */
+ if (mpol->mode == MPOL_PREFERRED_MANY) {
page = dequeue_huge_page_nodemask(h, gfp_mask | __GFP_RETRY_MAYFAIL,
nid, nodemask);
if (!page)
@@ -1984,7 +1984,7 @@ struct page *alloc_buddy_huge_page_with_mpol(struct hstate *h,
nodemask_t *nodemask;
nid = huge_node(vma, addr, gfp_mask, &mpol, &nodemask);
- if (mpol->mode != MPOL_BIND && nodemask) { /* AKA MPOL_PREFERRED_MANY */
+ if (mpol->mode != MPOL_PREFERRED_MANY) {
page = alloc_surplus_huge_page(h, gfp_mask | __GFP_RETRY_MAYFAIL,
nid, nodemask);
if (!page)
@@ -108,8 +108,6 @@
#include "internal.h"
-#define MPOL_PREFERRED_MANY MPOL_MAX
-
/* Internal flags */
#define MPOL_MF_DISCONTIG_OK (MPOL_MF_INTERNAL << 0) /* Skip checks for continuous vmas */
#define MPOL_MF_INVERT (MPOL_MF_INTERNAL << 1) /* Invert check for nodemask */
@@ -180,7 +178,7 @@ struct mempolicy *get_task_policy(struct task_struct *p)
static const struct mempolicy_operations {
int (*create)(struct mempolicy *pol, const nodemask_t *nodes);
void (*rebind)(struct mempolicy *pol, const nodemask_t *nodes);
-} mpol_ops[MPOL_MAX + 1];
+} mpol_ops[MPOL_MAX];
static inline int mpol_store_user_nodemask(const struct mempolicy *pol)
{
@@ -385,8 +383,8 @@ static void mpol_rebind_preferred_common(struct mempolicy *pol,
}
/* MPOL_PREFERRED_MANY allows multiple nodes to be set in 'nodes' */
-static void __maybe_unused mpol_rebind_preferred_many(struct mempolicy *pol,
- const nodemask_t *nodes)
+static void mpol_rebind_preferred_many(struct mempolicy *pol,
+ const nodemask_t *nodes)
{
mpol_rebind_preferred_common(pol, nodes, nodes);
}
@@ -448,7 +446,7 @@ void mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new)
mmap_write_unlock(mm);
}
-static const struct mempolicy_operations mpol_ops[MPOL_MAX + 1] = {
+static const struct mempolicy_operations mpol_ops[MPOL_MAX] = {
[MPOL_DEFAULT] = {
.rebind = mpol_rebind_default,
},
@@ -466,8 +464,8 @@ static const struct mempolicy_operations mpol_ops[MPOL_MAX + 1] = {
},
/* [MPOL_LOCAL] - see mpol_new() */
[MPOL_PREFERRED_MANY] = {
- .create = NULL,
- .rebind = NULL,
+ .create = mpol_new_preferred_many,
+ .rebind = mpol_rebind_preferred_many,
},
};
Adds a new mode to the existing mempolicy modes, MPOL_PREFERRED_MANY. MPOL_PREFERRED_MANY will be adequately documented in the internal admin-guide with this patch. Eventually, the man pages for mbind(2), get_mempolicy(2), set_mempolicy(2) and numactl(8) will also have text about this mode. Those shall contain the canonical reference. NUMA systems continue to become more prevalent. New technologies like PMEM make finer grain control over memory access patterns increasingly desirable. MPOL_PREFERRED_MANY allows userspace to specify a set of nodes that will be tried first when performing allocations. If those allocations fail, all remaining nodes will be tried. It's a straight forward API which solves many of the presumptive needs of system administrators wanting to optimize workloads on such machines. The mode will work either per VMA, or per thread. Generally speaking, this is similar to the way MPOL_BIND works, except the user will only get a SIGSEGV if all nodes in the system are unable to satisfy the allocation request. Link: https://lore.kernel.org/r/20200630212517.308045-13-ben.widawsky@intel.com Signed-off-by: Ben Widawsky <ben.widawsky@intel.com> --- .../admin-guide/mm/numa_memory_policy.rst | 16 ++++++++++++---- include/uapi/linux/mempolicy.h | 6 +++--- mm/hugetlb.c | 4 ++-- mm/mempolicy.c | 14 ++++++-------- 4 files changed, 23 insertions(+), 17 deletions(-)