The patch titled
cpusets: randomize node rotor used in cpuset_mem_spread_node()
has been added to the -mm tree. Its filename is
cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node.patch
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------------------------------------------------------
Subject: cpusets: randomize node rotor used in cpuset_mem_spread_node()
From: Michal Hocko <mhocko@xxxxxxx>
[This patch has already been accepted as 0ac0c0d but later reverted
(35926ff) because it itroduced arch specific __node_random which was
defined only for x86 code so it broke other archs. This is a followup
without any arch specific code. Other than that there are no functional
changes.]
Some workloads that create a large number of small files tend to assign
too many pages to node 0 (multi-node systems). Part of the reason is that
the rotor (in cpuset_mem_spread_node()) used to assign nodes starts at
node 0 for newly created tasks.
This patch changes the rotor to be initialized to a random node number of
the cpuset.
[akpm@xxxxxxxxxxxxxxxxxxxx: fix layout]
[Lee.Schermerhorn@xxxxxx: Define stub numa_random() for !NUMA configuration]
[mhocko@xxxxxxx: Make it arch independent]
Signed-off-by: Jack Steiner <steiner@xxxxxxx>
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@xxxxxx>
Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
Cc: Paul Menage <menage@xxxxxxxxxx>
Cc: Jack Steiner <steiner@xxxxxxx>
Cc: Robin Holt <holt@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/bitmap.h | 1 +
include/linux/nodemask.h | 7 +++++++
kernel/fork.c | 4 ++++
lib/bitmap.c | 2 +-
mm/mempolicy.c | 16 ++++++++++++++++
5 files changed, 29 insertions(+), 1 deletion(-)
diff -puN include/linux/bitmap.h~cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node include/linux/bitmap.h
--- a/include/linux/bitmap.h~cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node
+++ a/include/linux/bitmap.h
@@ -144,6 +144,7 @@ extern int bitmap_find_free_region(unsig
extern void bitmap_release_region(unsigned long *bitmap, int pos, int order);
extern int bitmap_allocate_region(unsigned long *bitmap, int pos, int order);
extern void bitmap_copy_le(void *dst, const unsigned long *src, int nbits);
+extern int bitmap_ord_to_pos(const unsigned long *bitmap, int n, int bits);
#define BITMAP_LAST_WORD_MASK(nbits) \
( \
diff -puN include/linux/nodemask.h~cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node include/linux/nodemask.h
--- a/include/linux/nodemask.h~cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node
+++ a/include/linux/nodemask.h
@@ -66,6 +66,8 @@
* int num_online_nodes() Number of online Nodes
* int num_possible_nodes() Number of all possible Nodes
*
+ * int node_random(mask) Random node with set bit in mask
+ *
* int node_online(node) Is some node online?
* int node_possible(node) Is some node possible?
*
@@ -430,6 +432,9 @@ static inline void node_set_offline(int
node_clear_state(nid, N_ONLINE);
nr_online_nodes = num_node_state(N_ONLINE);
}
+
+extern int node_random(const nodemask_t *maskp);
+
#else
static inline int node_state(int node, enum node_states state)
@@ -460,6 +465,8 @@ static inline int num_node_state(enum no
#define node_set_online(node) node_set_state((node), N_ONLINE)
#define node_set_offline(node) node_clear_state((node), N_ONLINE)
+
+static inline int node_random(const nodemask_t *mask) { return 0; }
#endif
#define node_online_map node_states[N_ONLINE]
diff -puN kernel/fork.c~cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node kernel/fork.c
--- a/kernel/fork.c~cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node
+++ a/kernel/fork.c
@@ -1125,6 +1125,10 @@ static struct task_struct *copy_process(
}
mpol_fix_fork_child_flag(p);
#endif
+#ifdef CONFIG_CPUSETS
+ p->cpuset_mem_spread_rotor = node_random(&p->mems_allowed);
+ p->cpuset_slab_spread_rotor = node_random(&p->mems_allowed);
+#endif
#ifdef CONFIG_TRACE_IRQFLAGS
p->irq_events = 0;
#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
diff -puN lib/bitmap.c~cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node lib/bitmap.c
--- a/lib/bitmap.c~cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node
+++ a/lib/bitmap.c
@@ -756,7 +756,7 @@ static int bitmap_pos_to_ord(const unsig
*
* The bit positions 0 through @bits are valid positions in @buf.
*/
-static int bitmap_ord_to_pos(const unsigned long *buf, int ord, int bits)
+int bitmap_ord_to_pos(const unsigned long *buf, int ord, int bits)
{
int pos = 0;
diff -puN mm/mempolicy.c~cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node mm/mempolicy.c
--- a/mm/mempolicy.c~cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node
+++ a/mm/mempolicy.c
@@ -93,6 +93,7 @@
#include <asm/tlbflush.h>
#include <asm/uaccess.h>
+#include <linux/random.h>
#include "internal.h"
@@ -1649,6 +1650,21 @@ static inline unsigned interleave_nid(st
return interleave_nodes(pol);
}
+/*
+ * Return the bit number of a random bit set in the nodemask.
+ * (returns -1 if nodemask is empty)
+ */
+int node_random(const nodemask_t *maskp)
+{
+ int w, bit = -1;
+
+ w = nodes_weight(*maskp);
+ if (w)
+ bit = bitmap_ord_to_pos(maskp->bits,
+ get_random_int() % w, MAX_NUMNODES);
+ return bit;
+}
+
#ifdef CONFIG_HUGETLBFS
/*
* huge_zonelist(@vma, @addr, @gfp_flags, @mpol)
_
Patches currently in -mm which might be from mhocko@xxxxxxx are
memsw-remove-noswapaccount-kernel-parameter.patch
memcg-remove-pointless-next_mz-nullification-in-mem_cgroup_soft_limit_reclaim.patch
memcg-mark-init_section_page_cgroup-properly.patch
memcg-fix-off-by-one-when-calculating-swap-cgroup-map-length.patch
memcg-move-page-freeing-code-out-of-lock.patch
maintainers-add-mm-page_cgroupc-into-memcg-subsystem.patch
cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node.patch
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