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Subject[PATCH v9 08/13] memcg: dirty page accounting support routines
Date
Added memcg dirty page accounting support routines.  These routines are
used by later changes to provide memcg aware writeback and dirty page
limiting. A mem_cgroup_dirty_info() tracepoint is is also included to
allow for easier understanding of memcg writeback operation.

Signed-off-by: Greg Thelen <gthelen@google.com>
---
Changelog since v8:
- Use 'memcg' rather than 'mem' for local variables and parameters.
This is consistent with other memory controller code.
include/linux/memcontrol.h | 9 ++
include/trace/events/memcontrol.h | 34 +++++++++
mm/memcontrol.c | 147 +++++++++++++++++++++++++++++++++++++
3 files changed, 190 insertions(+), 0 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 630d3fa..9cc8841 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -36,6 +36,15 @@ 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 */
+};
+
+struct dirty_info {
+ unsigned long dirty_thresh;
+ unsigned long background_thresh;
+ unsigned long nr_file_dirty;
+ unsigned long nr_writeback;
+ unsigned long nr_unstable_nfs;
};

extern unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
diff --git a/include/trace/events/memcontrol.h b/include/trace/events/memcontrol.h
index 781ef9fc..abf1306 100644
--- a/include/trace/events/memcontrol.h
+++ b/include/trace/events/memcontrol.h
@@ -26,6 +26,40 @@ TRACE_EVENT(mem_cgroup_mark_inode_dirty,
TP_printk("ino=%ld css_id=%d", __entry->ino, __entry->css_id)
)

+TRACE_EVENT(mem_cgroup_dirty_info,
+ TP_PROTO(unsigned short css_id,
+ struct dirty_info *dirty_info),
+
+ TP_ARGS(css_id, dirty_info),
+
+ TP_STRUCT__entry(
+ __field(unsigned short, css_id)
+ __field(unsigned long, dirty_thresh)
+ __field(unsigned long, background_thresh)
+ __field(unsigned long, nr_file_dirty)
+ __field(unsigned long, nr_writeback)
+ __field(unsigned long, nr_unstable_nfs)
+ ),
+
+ TP_fast_assign(
+ __entry->css_id = css_id;
+ __entry->dirty_thresh = dirty_info->dirty_thresh;
+ __entry->background_thresh = dirty_info->background_thresh;
+ __entry->nr_file_dirty = dirty_info->nr_file_dirty;
+ __entry->nr_writeback = dirty_info->nr_writeback;
+ __entry->nr_unstable_nfs = dirty_info->nr_unstable_nfs;
+ ),
+
+ TP_printk("css_id=%d thresh=%ld bg_thresh=%ld dirty=%ld wb=%ld "
+ "unstable_nfs=%ld",
+ __entry->css_id,
+ __entry->dirty_thresh,
+ __entry->background_thresh,
+ __entry->nr_file_dirty,
+ __entry->nr_writeback,
+ __entry->nr_unstable_nfs)
+)
+
#endif /* _TRACE_MEMCONTROL_H */

/* This part must be outside protection */
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 4e01699..d54adf4 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1366,6 +1366,11 @@ int mem_cgroup_swappiness(struct mem_cgroup *memcg)
return memcg->swappiness;
}

+static unsigned long dirty_info_reclaimable(struct dirty_info *info)
+{
+ return info->nr_file_dirty + info->nr_unstable_nfs;
+}
+
/*
* 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
@@ -1396,6 +1401,148 @@ static void mem_cgroup_dirty_param(struct vm_dirty_param *param,
}
}

+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 *memcg,
+ enum mem_cgroup_page_stat_item item)
+{
+ s64 ret;
+
+ switch (item) {
+ case MEMCG_NR_FILE_DIRTY:
+ ret = mem_cgroup_read_stat(memcg, MEM_CGROUP_STAT_FILE_DIRTY);
+ break;
+ case MEMCG_NR_FILE_WRITEBACK:
+ ret = mem_cgroup_read_stat(memcg,
+ MEM_CGROUP_STAT_FILE_WRITEBACK);
+ break;
+ case MEMCG_NR_FILE_UNSTABLE_NFS:
+ ret = mem_cgroup_read_stat(memcg,
+ MEM_CGROUP_STAT_FILE_UNSTABLE_NFS);
+ break;
+ case MEMCG_NR_DIRTYABLE_PAGES:
+ ret = mem_cgroup_read_stat(memcg, LRU_ACTIVE_FILE) +
+ mem_cgroup_read_stat(memcg, LRU_INACTIVE_FILE);
+ if (mem_cgroup_can_swap(memcg))
+ ret += mem_cgroup_read_stat(memcg, LRU_ACTIVE_ANON) +
+ mem_cgroup_read_stat(memcg, LRU_INACTIVE_ANON);
+ break;
+ default:
+ BUG();
+ break;
+ }
+ return ret;
+}
+
+/*
+ * Return the number of additional pages that the @memcg 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 *memcg)
+{
+ u64 free;
+ unsigned long min_free;
+
+ min_free = global_page_state(NR_FREE_PAGES);
+
+ while (memcg) {
+ free = (res_counter_read_u64(&memcg->res, RES_LIMIT) -
+ res_counter_read_u64(&memcg->res, RES_USAGE)) >>
+ PAGE_SHIFT;
+ min_free = min_t(u64, min_free, free);
+ memcg = parent_mem_cgroup(memcg);
+ }
+
+ return min_free;
+}
+
+/*
+ * mem_cgroup_page_stat() - get memory cgroup file cache statistics
+ * @memcg: memory cgroup to query
+ * @item: memory statistic item exported to the kernel
+ *
+ * Return the accounted statistic value.
+ */
+static unsigned long mem_cgroup_page_stat(struct mem_cgroup *memcg,
+ enum mem_cgroup_page_stat_item item)
+{
+ struct mem_cgroup *iter;
+ s64 value;
+
+ /*
+ * 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(memcg);
+ else
+ value = 0;
+
+ /*
+ * Recursively evaluate page statistics against all cgroup under
+ * hierarchy tree
+ */
+ for_each_mem_cgroup_tree(iter, memcg)
+ 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;
+}
+
+/* Return dirty thresholds and usage for @memcg. */
+static void mem_cgroup_dirty_info(unsigned long sys_available_mem,
+ struct mem_cgroup *memcg,
+ struct dirty_info *info)
+{
+ unsigned long uninitialized_var(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);
+
+ trace_mem_cgroup_dirty_info(css_id(&memcg->css), info);
+}
+
static void mem_cgroup_start_move(struct mem_cgroup *mem)
{
int cpu;
--
1.7.3.1


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