[PATCH v5 7/9] memcg: add dirty limits to mem_cgroup
Greg Thelen
gthelen at google.com
Fri Feb 25 13:35:58 PST 2011
Extend mem_cgroup to contain dirty page limits. Also add routines
allowing the kernel to query the dirty usage of a memcg.
These interfaces not used by the kernel yet. A subsequent commit
will add kernel calls to utilize these new routines.
Signed-off-by: Greg Thelen <gthelen at google.com>
Signed-off-by: Andrea Righi <arighi at develer.com>
Signed-off-by: Johannes Weiner <hannes at cmpxchg.org>
---
Changelog since v4:
- Added support for hierarchical dirty limits.
- Simplified __mem_cgroup_dirty_param().
- Simplified mem_cgroup_page_stat().
- Deleted mem_cgroup_nr_pages_item enum, which was added little value.
Instead the mem_cgroup_page_stat_item enum values are used to identify
memcg dirty statistics exported to kernel.
- Fixed overflow issues in mem_cgroup_hierarchical_free_pages().
Changelog since v3:
- Previously memcontrol.c used struct vm_dirty_param and vm_dirty_param() to
advertise dirty memory limits. Now struct dirty_info and
mem_cgroup_dirty_info() is used to share dirty limits between memcontrol and
the rest of the kernel.
- __mem_cgroup_has_dirty_limit() now returns false if use_hierarchy is set.
- memcg_hierarchical_free_pages() now uses parent_mem_cgroup() and is simpler.
- created internal routine, __mem_cgroup_has_dirty_limit(), to consolidate the
logic.
Changelog since v1:
- Rename (for clarity):
- mem_cgroup_write_page_stat_item -> mem_cgroup_page_stat_item
- mem_cgroup_read_page_stat_item -> mem_cgroup_nr_pages_item
- Removed unnecessary get_ prefix from get_xxx() functions.
- Avoid lockdep warnings by using rcu_read_[un]lock() in
mem_cgroup_has_dirty_limit().
include/linux/memcontrol.h | 28 +++++
mm/memcontrol.c | 269 +++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 296 insertions(+), 1 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index e1f70a9..8c00c06 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -19,6 +19,7 @@
#ifndef _LINUX_MEMCONTROL_H
#define _LINUX_MEMCONTROL_H
+#include <linux/writeback.h>
#include <linux/cgroup.h>
struct mem_cgroup;
struct page_cgroup;
@@ -31,6 +32,7 @@ enum mem_cgroup_page_stat_item {
MEMCG_NR_FILE_DIRTY, /* # of dirty pages in page cache */
MEMCG_NR_FILE_WRITEBACK, /* # of pages under writeback */
MEMCG_NR_FILE_UNSTABLE_NFS, /* # of NFS unstable pages */
+ MEMCG_NR_DIRTYABLE_PAGES, /* # of pages that could be dirty */
};
extern unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
@@ -145,6 +147,13 @@ static inline void mem_cgroup_dec_page_stat(struct page *page,
mem_cgroup_update_page_stat(page, idx, -1);
}
+bool mem_cgroup_has_dirty_limit(void);
+bool mem_cgroup_hierarchical_dirty_info(unsigned long sys_available_mem,
+ struct mem_cgroup *memcg,
+ struct dirty_info *info);
+unsigned long mem_cgroup_page_stat(struct mem_cgroup *mem,
+ enum mem_cgroup_page_stat_item item);
+
unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
gfp_t gfp_mask);
u64 mem_cgroup_get_limit(struct mem_cgroup *mem);
@@ -333,6 +342,25 @@ static inline void mem_cgroup_dec_page_stat(struct page *page,
{
}
+static inline bool mem_cgroup_has_dirty_limit(void)
+{
+ return false;
+}
+
+static inline bool
+mem_cgroup_hierarchical_dirty_info(unsigned long sys_available_mem,
+ struct mem_cgroup *memcg,
+ struct dirty_info *info)
+{
+ return false;
+}
+
+static inline unsigned long mem_cgroup_page_stat(struct mem_cgroup *mem,
+ enum mem_cgroup_page_stat_item item)
+{
+ return -ENOSYS;
+}
+
static inline
unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
gfp_t gfp_mask)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 38f786b..bc86329 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -198,6 +198,14 @@ struct mem_cgroup_eventfd_list {
static void mem_cgroup_threshold(struct mem_cgroup *mem);
static void mem_cgroup_oom_notify(struct mem_cgroup *mem);
+/* Dirty memory parameters */
+struct vm_dirty_param {
+ int dirty_ratio;
+ int dirty_background_ratio;
+ unsigned long dirty_bytes;
+ unsigned long dirty_background_bytes;
+};
+
/*
* The memory controller data structure. The memory controller controls both
* page cache and RSS per cgroup. We would eventually like to provide
@@ -237,6 +245,10 @@ struct mem_cgroup {
atomic_t refcnt;
unsigned int swappiness;
+
+ /* control memory cgroup dirty pages */
+ struct vm_dirty_param dirty_param;
+
/* OOM-Killer disable */
int oom_kill_disable;
@@ -1128,6 +1140,254 @@ static unsigned int get_swappiness(struct mem_cgroup *memcg)
return memcg->swappiness;
}
+/*
+ * Return true if the current memory cgroup has local dirty memory settings.
+ * There is an allowed race between the current task migrating in-to/out-of the
+ * root cgroup while this routine runs. So the return value may be incorrect if
+ * the current task is being simultaneously migrated.
+ */
+static bool __mem_cgroup_has_dirty_limit(struct mem_cgroup *mem)
+{
+ return mem && !mem_cgroup_is_root(mem);
+}
+
+bool mem_cgroup_has_dirty_limit(void)
+{
+ struct mem_cgroup *mem;
+ bool ret;
+
+ if (mem_cgroup_disabled())
+ return false;
+
+ rcu_read_lock();
+ mem = mem_cgroup_from_task(current);
+ ret = __mem_cgroup_has_dirty_limit(mem);
+ rcu_read_unlock();
+
+ return ret;
+}
+
+/*
+ * Returns a snapshot of the current dirty limits which is not synchronized with
+ * the routines that change the dirty limits. If this routine races with an
+ * update to the dirty bytes/ratio value, then the caller must handle the case
+ * where neither dirty_[background_]_ratio nor _bytes are set.
+ */
+static void __mem_cgroup_dirty_param(struct vm_dirty_param *param,
+ struct mem_cgroup *mem)
+{
+ if (__mem_cgroup_has_dirty_limit(mem)) {
+ *param = mem->dirty_param;
+ } else {
+ param->dirty_ratio = vm_dirty_ratio;
+ param->dirty_bytes = vm_dirty_bytes;
+ param->dirty_background_ratio = dirty_background_ratio;
+ param->dirty_background_bytes = dirty_background_bytes;
+ }
+}
+
+/* Return dirty thresholds and usage metrics for @memcg. */
+static void mem_cgroup_dirty_info(unsigned long sys_available_mem,
+ struct mem_cgroup *memcg,
+ struct dirty_info *info)
+{
+ unsigned long available_mem;
+ struct vm_dirty_param dirty_param;
+
+ __mem_cgroup_dirty_param(&dirty_param, memcg);
+
+ if (!dirty_param.dirty_bytes || !dirty_param.dirty_background_bytes)
+ available_mem = min(
+ sys_available_mem,
+ mem_cgroup_page_stat(memcg, MEMCG_NR_DIRTYABLE_PAGES));
+
+ if (dirty_param.dirty_bytes)
+ info->dirty_thresh =
+ DIV_ROUND_UP(dirty_param.dirty_bytes, PAGE_SIZE);
+ else
+ info->dirty_thresh =
+ (dirty_param.dirty_ratio * available_mem) / 100;
+
+ if (dirty_param.dirty_background_bytes)
+ info->background_thresh =
+ DIV_ROUND_UP(dirty_param.dirty_background_bytes,
+ PAGE_SIZE);
+ else
+ info->background_thresh =
+ (dirty_param.dirty_background_ratio *
+ available_mem) / 100;
+
+ info->nr_file_dirty = mem_cgroup_page_stat(memcg, MEMCG_NR_FILE_DIRTY);
+ info->nr_writeback = mem_cgroup_page_stat(memcg,
+ MEMCG_NR_FILE_WRITEBACK);
+ info->nr_unstable_nfs =
+ mem_cgroup_page_stat(memcg, MEMCG_NR_FILE_UNSTABLE_NFS);
+}
+
+/*
+ * Return the dirty thresholds and usage metrics for the memcg (within the
+ * ancestral chain of @memcg) closest to its limit. If @memcg is not set, then
+ * use the current task's memcg.
+ *
+ * The current task may be moved to another cgroup while this routine accesses
+ * the dirty limit. But a precise check is meaningless because the task can be
+ * moved after our access and writeback tends to take long time. At least,
+ * "memcg" will not be freed while holding rcu_read_lock().
+ */
+bool mem_cgroup_hierarchical_dirty_info(unsigned long sys_available_mem,
+ struct mem_cgroup *memcg,
+ struct dirty_info *info)
+{
+ unsigned long usage;
+ struct dirty_info uninitialized_var(cur_info);
+
+ if (mem_cgroup_disabled())
+ return false;
+
+ info->nr_writeback = ULONG_MAX; /* invalid initial value */
+
+ /*
+ * Routine within mem_cgroup_page_stat() need online cpus locked.
+ * get_online_cpus() can sleep so it must be called before
+ * rcu_read_lock().
+ */
+ get_online_cpus();
+ rcu_read_lock();
+ if (!memcg)
+ memcg = mem_cgroup_from_task(current);
+
+ while (__mem_cgroup_has_dirty_limit(memcg)) {
+ mem_cgroup_dirty_info(sys_available_mem, memcg, &cur_info);
+ usage = dirty_info_reclaimable(&cur_info) +
+ cur_info.nr_writeback;
+
+ if (!memcg->use_hierarchy || usage >= cur_info.dirty_thresh) {
+ *info = cur_info;
+ break;
+ }
+
+ /* save dirty stats for memcg closest to its limit */
+ if ((info->nr_writeback == ULONG_MAX) ||
+ (cur_info.dirty_thresh - usage <
+ info->dirty_thresh - dirty_info_reclaimable(info) -
+ info->nr_writeback))
+ *info = cur_info;
+
+ /* continue walking up hierarchy enabled parents */
+ memcg = parent_mem_cgroup(memcg);
+ if (!memcg || !memcg->use_hierarchy)
+ break;
+ }
+
+ rcu_read_unlock();
+ put_online_cpus();
+ return info->nr_writeback != ULONG_MAX;
+}
+
+static inline bool mem_cgroup_can_swap(struct mem_cgroup *memcg)
+{
+ if (!do_swap_account)
+ return nr_swap_pages > 0;
+ return !memcg->memsw_is_minimum &&
+ (res_counter_read_u64(&memcg->memsw, RES_LIMIT) > 0);
+}
+
+static s64 mem_cgroup_local_page_stat(struct mem_cgroup *mem,
+ enum mem_cgroup_page_stat_item item)
+{
+ s64 ret;
+
+ switch (item) {
+ case MEMCG_NR_FILE_DIRTY:
+ ret = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_FILE_DIRTY);
+ break;
+ case MEMCG_NR_FILE_WRITEBACK:
+ ret = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_FILE_WRITEBACK);
+ break;
+ case MEMCG_NR_FILE_UNSTABLE_NFS:
+ ret = mem_cgroup_read_stat(mem,
+ MEM_CGROUP_STAT_FILE_UNSTABLE_NFS);
+ break;
+ case MEMCG_NR_DIRTYABLE_PAGES:
+ ret = mem_cgroup_read_stat(mem, LRU_ACTIVE_FILE) +
+ mem_cgroup_read_stat(mem, LRU_INACTIVE_FILE);
+ if (mem_cgroup_can_swap(mem))
+ ret += mem_cgroup_read_stat(mem, LRU_ACTIVE_ANON) +
+ mem_cgroup_read_stat(mem, LRU_INACTIVE_ANON);
+ break;
+ default:
+ BUG();
+ break;
+ }
+ return ret;
+}
+
+/*
+ * Return the number of additional pages that the @mem cgroup could allocate.
+ * If use_hierarchy is set, then this involves checking parent mem cgroups to
+ * find the cgroup with the smallest free space.
+ */
+static unsigned long
+mem_cgroup_hierarchical_free_pages(struct mem_cgroup *mem)
+{
+ u64 free;
+ unsigned long min_free;
+
+ min_free = global_page_state(NR_FREE_PAGES);
+
+ while (mem) {
+ free = (res_counter_read_u64(&mem->res, RES_LIMIT) -
+ res_counter_read_u64(&mem->res, RES_USAGE)) >>
+ PAGE_SHIFT;
+ min_free = min((u64)min_free, free);
+ mem = parent_mem_cgroup(mem);
+ }
+
+ return min_free;
+}
+
+/*
+ * mem_cgroup_page_stat() - get memory cgroup file cache statistics
+ * @mem: memory cgroup to query
+ * @item: memory statistic item exported to the kernel
+ *
+ * Return the accounted statistic value.
+ */
+unsigned long mem_cgroup_page_stat(struct mem_cgroup *mem,
+ enum mem_cgroup_page_stat_item item)
+{
+ struct mem_cgroup *iter;
+ s64 value;
+
+ VM_BUG_ON(!mem);
+ VM_BUG_ON(mem_cgroup_is_root(mem));
+
+ /*
+ * If we're looking for dirtyable pages we need to evaluate free pages
+ * depending on the limit and usage of the parents first of all.
+ */
+ if (item == MEMCG_NR_DIRTYABLE_PAGES)
+ value = mem_cgroup_hierarchical_free_pages(mem);
+ else
+ value = 0;
+
+ /*
+ * Recursively evaluate page statistics against all cgroup under
+ * hierarchy tree
+ */
+ for_each_mem_cgroup_tree(iter, mem)
+ value += mem_cgroup_local_page_stat(iter, item);
+
+ /*
+ * Summing of unlocked per-cpu counters is racy and may yield a slightly
+ * negative value. Zero is the only sensible value in such cases.
+ */
+ if (unlikely(value < 0))
+ value = 0;
+
+ return value;
+}
+
static void mem_cgroup_start_move(struct mem_cgroup *mem)
{
int cpu;
@@ -4578,8 +4838,15 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
mem->last_scanned_child = 0;
INIT_LIST_HEAD(&mem->oom_notify);
- if (parent)
+ if (parent) {
mem->swappiness = get_swappiness(parent);
+ __mem_cgroup_dirty_param(&mem->dirty_param, parent);
+ } else {
+ /*
+ * The root cgroup dirty_param field is not used, instead,
+ * system-wide dirty limits are used.
+ */
+ }
atomic_set(&mem->refcnt, 1);
mem->move_charge_at_immigrate = 0;
mutex_init(&mem->thresholds_lock);
--
1.7.3.1
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