[Devel] [RFC] [PATCH] memcg: cleanup memory thresholds
Kirill A. Shutemov
kirill at shutemov.name
Sat May 8 17:11:12 PDT 2010
Introduce struct mem_cgroup_thresholds. It helps to reduce number of
checks of thresholds type (memory or mem+swap).
Signed-off-by: Kirill A. Shutemov <kirill at shutemov.name>
---
mm/memcontrol.c | 151 ++++++++++++++++++++++++-------------------------------
1 files changed, 66 insertions(+), 85 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a6d2a4c..a6c6268 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -158,6 +158,18 @@ struct mem_cgroup_threshold_ary {
/* Array of thresholds */
struct mem_cgroup_threshold entries[0];
};
+
+struct mem_cgroup_thresholds {
+ /* Primary thresholds array */
+ struct mem_cgroup_threshold_ary *primary;
+ /*
+ * Spare threshold array.
+ * It needed to make mem_cgroup_unregister_event() "never fail".
+ * It must be able to store at least primary->size - 1 entires.
+ */
+ struct mem_cgroup_threshold_ary *spare;
+};
+
/* for OOM */
struct mem_cgroup_eventfd_list {
struct list_head list;
@@ -224,20 +236,10 @@ struct mem_cgroup {
struct mutex thresholds_lock;
/* thresholds for memory usage. RCU-protected */
- struct mem_cgroup_threshold_ary *thresholds;
-
- /*
- * Preallocated buffer to be used in mem_cgroup_unregister_event()
- * to make it "never fail".
- * It must be able to store at least thresholds->size - 1 entries.
- */
- struct mem_cgroup_threshold_ary *__thresholds;
+ struct mem_cgroup_thresholds thresholds;
/* thresholds for mem+swap usage. RCU-protected */
- struct mem_cgroup_threshold_ary *memsw_thresholds;
-
- /* the same as __thresholds, but for memsw_thresholds */
- struct mem_cgroup_threshold_ary *__memsw_thresholds;
+ struct mem_cgroup_thresholds memsw_thresholds;
/* For oom notifier event fd */
struct list_head oom_notify;
@@ -3438,9 +3440,9 @@ static void __mem_cgroup_threshold(struct mem_cgroup *memcg, bool swap)
rcu_read_lock();
if (!swap)
- t = rcu_dereference(memcg->thresholds);
+ t = rcu_dereference(memcg->thresholds.primary);
else
- t = rcu_dereference(memcg->memsw_thresholds);
+ t = rcu_dereference(memcg->memsw_thresholds.primary);
if (!t)
goto unlock;
@@ -3514,91 +3516,78 @@ static int mem_cgroup_usage_register_event(struct cgroup *cgrp,
struct cftype *cft, struct eventfd_ctx *eventfd, const char *args)
{
struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
- struct mem_cgroup_threshold_ary *thresholds, *thresholds_new;
+ struct mem_cgroup_thresholds *thresholds;
+ struct mem_cgroup_threshold_ary *new;
int type = MEMFILE_TYPE(cft->private);
u64 threshold, usage;
- int size;
- int i, ret;
+ int i, size, ret;
ret = res_counter_memparse_write_strategy(args, &threshold);
if (ret)
return ret;
mutex_lock(&memcg->thresholds_lock);
+
if (type == _MEM)
- thresholds = memcg->thresholds;
+ thresholds = &memcg->thresholds;
else if (type == _MEMSWAP)
- thresholds = memcg->memsw_thresholds;
+ thresholds = &memcg->memsw_thresholds;
else
BUG();
usage = mem_cgroup_usage(memcg, type == _MEMSWAP);
/* Check if a threshold crossed before adding a new one */
- if (thresholds)
+ if (thresholds->primary)
__mem_cgroup_threshold(memcg, type == _MEMSWAP);
- if (thresholds)
- size = thresholds->size + 1;
- else
- size = 1;
+ size = thresholds->primary ? thresholds->primary->size + 1 : 1;
/* Allocate memory for new array of thresholds */
- thresholds_new = kmalloc(sizeof(*thresholds_new) +
- size * sizeof(struct mem_cgroup_threshold),
+ new = kmalloc(sizeof(*new) + size * sizeof(struct mem_cgroup_threshold),
GFP_KERNEL);
- if (!thresholds_new) {
+ if (!new) {
ret = -ENOMEM;
goto unlock;
}
- thresholds_new->size = size;
+ new->size = size;
/* Copy thresholds (if any) to new array */
- if (thresholds)
- memcpy(thresholds_new->entries, thresholds->entries,
- thresholds->size *
+ if (thresholds->primary) {
+ memcpy(new->entries, thresholds->primary->entries, (size - 1) *
sizeof(struct mem_cgroup_threshold));
+ }
+
/* Add new threshold */
- thresholds_new->entries[size - 1].eventfd = eventfd;
- thresholds_new->entries[size - 1].threshold = threshold;
+ new->entries[size - 1].eventfd = eventfd;
+ new->entries[size - 1].threshold = threshold;
/* Sort thresholds. Registering of new threshold isn't time-critical */
- sort(thresholds_new->entries, size,
- sizeof(struct mem_cgroup_threshold),
+ sort(new->entries, size, sizeof(struct mem_cgroup_threshold),
compare_thresholds, NULL);
/* Find current threshold */
- thresholds_new->current_threshold = -1;
+ new->current_threshold = -1;
for (i = 0; i < size; i++) {
- if (thresholds_new->entries[i].threshold < usage) {
+ if (new->entries[i].threshold < usage) {
/*
- * thresholds_new->current_threshold will not be used
- * until rcu_assign_pointer(), so it's safe to increment
+ * new->current_threshold will not be used until
+ * rcu_assign_pointer(), so it's safe to increment
* it here.
*/
- ++thresholds_new->current_threshold;
+ ++new->current_threshold;
}
}
- if (type == _MEM)
- rcu_assign_pointer(memcg->thresholds, thresholds_new);
- else
- rcu_assign_pointer(memcg->memsw_thresholds, thresholds_new);
+ /* Free old spare buffer and save old primary buffer as spare */
+ kfree(thresholds->spare);
+ thresholds->spare = thresholds->primary;
+
+ rcu_assign_pointer(thresholds->primary, new);
/* To be sure that nobody uses thresholds */
synchronize_rcu();
- /*
- * Free old preallocated buffer and use thresholds as new
- * preallocated buffer.
- */
- if (type == _MEM) {
- kfree(memcg->__thresholds);
- memcg->__thresholds = thresholds;
- } else {
- kfree(memcg->__memsw_thresholds);
- memcg->__memsw_thresholds = thresholds;
- }
unlock:
mutex_unlock(&memcg->thresholds_lock);
@@ -3609,17 +3598,17 @@ static void mem_cgroup_usage_unregister_event(struct cgroup *cgrp,
struct cftype *cft, struct eventfd_ctx *eventfd)
{
struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
- struct mem_cgroup_threshold_ary *thresholds, *thresholds_new;
+ struct mem_cgroup_thresholds *thresholds;
+ struct mem_cgroup_threshold_ary *new;
int type = MEMFILE_TYPE(cft->private);
u64 usage;
- int size = 0;
- int i, j;
+ int i, j, size;
mutex_lock(&memcg->thresholds_lock);
if (type == _MEM)
- thresholds = memcg->thresholds;
+ thresholds = &memcg->thresholds;
else if (type == _MEMSWAP)
- thresholds = memcg->memsw_thresholds;
+ thresholds = &memcg->memsw_thresholds;
else
BUG();
@@ -3635,53 +3624,45 @@ static void mem_cgroup_usage_unregister_event(struct cgroup *cgrp,
__mem_cgroup_threshold(memcg, type == _MEMSWAP);
/* Calculate new number of threshold */
- for (i = 0; i < thresholds->size; i++) {
- if (thresholds->entries[i].eventfd != eventfd)
+ size = 0;
+ for (i = 0; i < thresholds->primary->size; i++) {
+ if (thresholds->primary->entries[i].eventfd != eventfd)
size++;
}
- /* Use preallocated buffer for new array of thresholds */
- if (type == _MEM)
- thresholds_new = memcg->__thresholds;
- else
- thresholds_new = memcg->__memsw_thresholds;
+ new = thresholds->spare;
/* Set thresholds array to NULL if we don't have thresholds */
if (!size) {
- kfree(thresholds_new);
- thresholds_new = NULL;
+ kfree(new);
+ new = NULL;
goto swap_buffers;
}
- thresholds_new->size = size;
+ new->size = size;
/* Copy thresholds and find current threshold */
- thresholds_new->current_threshold = -1;
- for (i = 0, j = 0; i < thresholds->size; i++) {
- if (thresholds->entries[i].eventfd == eventfd)
+ new->current_threshold = -1;
+ for (i = 0, j = 0; i < thresholds->primary->size; i++) {
+ if (thresholds->primary->entries[i].eventfd == eventfd)
continue;
- thresholds_new->entries[j] = thresholds->entries[i];
- if (thresholds_new->entries[j].threshold < usage) {
+ new->entries[j] = thresholds->primary->entries[i];
+ if (new->entries[j].threshold < usage) {
/*
- * thresholds_new->current_threshold will not be used
+ * new->current_threshold will not be used
* until rcu_assign_pointer(), so it's safe to increment
* it here.
*/
- ++thresholds_new->current_threshold;
+ ++new->current_threshold;
}
j++;
}
swap_buffers:
- /* Swap thresholds array and preallocated buffer */
- if (type == _MEM) {
- memcg->__thresholds = thresholds;
- rcu_assign_pointer(memcg->thresholds, thresholds_new);
- } else {
- memcg->__memsw_thresholds = thresholds;
- rcu_assign_pointer(memcg->memsw_thresholds, thresholds_new);
- }
+ /* Swap primary and spare array */
+ thresholds->spare = thresholds->primary;
+ rcu_assign_pointer(thresholds->primary, new);
/* To be sure that nobody uses thresholds */
synchronize_rcu();
--
1.7.0.4
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