[PATCH v2 2/6] mm, mempolicy: stop adjusting current->il_next in mpol_rebind_nodemask()
From: Vlastimil Babka <hidden>
Date: 2017-05-17 08:12:57
Also in:
cgroups, linux-mm, lkml
Subsystem:
memory management, memory management - memory policy and migration, scheduler, the rest · Maintainers:
Andrew Morton, David Hildenbrand, Ingo Molnar, Peter Zijlstra, Juri Lelli, Vincent Guittot, Linus Torvalds
The task->il_next variable stores the next allocation node id for task's MPOL_INTERLEAVE policy. mpol_rebind_nodemask() updates interleave and bind mempolicies due to changing cpuset mems. Currently it also tries to make sure that current->il_next is valid within the updated nodemask. This is bogus, because 1) we are updating potentially any task's mempolicy, not just current, and 2) we might be updating a per-vma mempolicy, not task one. The interleave_nodes() function that uses il_next can cope fine with the value not being within the currently allowed nodes, so this hasn't manifested as an actual issue. We can remove the need for updating il_next completely by changing it to il_prev and store the node id of the previous interleave allocation instead of the next id. Then interleave_nodes() can calculate the next id using the current nodemask and also store it as il_prev, except when querying the next node via do_get_mempolicy(). Signed-off-by: Vlastimil Babka <redacted> --- include/linux/sched.h | 2 +- mm/mempolicy.c | 22 +++++++--------------- 2 files changed, 8 insertions(+), 16 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6a97386c785e..b72bbfec01f9 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h@@ -884,7 +884,7 @@ struct task_struct { #ifdef CONFIG_NUMA /* Protected by alloc_lock: */ struct mempolicy *mempolicy; - short il_next; + short il_prev; short pref_node_fork; #endif #ifdef CONFIG_NUMA_BALANCING
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 37d0b334bfe9..d77177c7283b 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c@@ -349,12 +349,6 @@ static void mpol_rebind_nodemask(struct mempolicy *pol, const nodemask_t *nodes, pol->v.nodes = tmp; else BUG(); - - if (!node_isset(current->il_next, tmp)) { - current->il_next = next_node_in(current->il_next, tmp); - if (current->il_next >= MAX_NUMNODES) - current->il_next = numa_node_id(); - } } static void mpol_rebind_preferred(struct mempolicy *pol,
@@ -812,9 +806,8 @@ static long do_set_mempolicy(unsigned short mode, unsigned short flags, } old = current->mempolicy; current->mempolicy = new; - if (new && new->mode == MPOL_INTERLEAVE && - nodes_weight(new->v.nodes)) - current->il_next = first_node(new->v.nodes); + if (new && new->mode == MPOL_INTERLEAVE) + current->il_prev = MAX_NUMNODES-1; task_unlock(current); mpol_put(old); ret = 0;
@@ -916,7 +909,7 @@ static long do_get_mempolicy(int *policy, nodemask_t *nmask, *policy = err; } else if (pol == current->mempolicy && pol->mode == MPOL_INTERLEAVE) { - *policy = current->il_next; + *policy = next_node_in(current->il_prev, pol->v.nodes); } else { err = -EINVAL; goto out;
@@ -1697,14 +1690,13 @@ static struct zonelist *policy_zonelist(gfp_t gfp, struct mempolicy *policy, /* Do dynamic interleaving for a process */ static unsigned interleave_nodes(struct mempolicy *policy) { - unsigned nid, next; + unsigned next; struct task_struct *me = current; - nid = me->il_next; - next = next_node_in(nid, policy->v.nodes); + next = next_node_in(me->il_prev, policy->v.nodes); if (next < MAX_NUMNODES) - me->il_next = next; - return nid; + me->il_prev = next; + return next; } /*
--
2.12.2
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