[PATCH][v3.1] blkio: Add io controller stats like

From: Divyesh Shah
Date: Tue Apr 06 2010 - 19:28:55 EST

- io_service_time (the total time between request dispatch and completion for
all IOs in the cgroup)
- io_wait_time (the total time spent waiting by all IOs in this cgroup in the IO
scheduler queues before getting serviced)
- io_serviced (number of IOs serviced from this blkio_group)
- io_service_bytes (Number of bytes served for this cgroup)

These stats are accumulated per operation type helping us to distinguish between
read and write, and sync and async IO. This patch does not increment any of
these stats.

Changelog from v3:
o renamed blkiocg_reset_write to blkiocg_reset_stats
o more clarification in the documentation on io_service_time and io_wait_time.

Signed-off-by: Divyesh Shah<dpshah@xxxxxxxxxx>
---

Documentation/cgroups/blkio-controller.txt | 48 ++++++++
block/blk-cgroup.c | 166 +++++++++++++++++++++++++---
block/blk-cgroup.h | 60 ++++++++--
block/cfq-iosched.c | 3 -
4 files changed, 247 insertions(+), 30 deletions(-)

diff --git a/Documentation/cgroups/blkio-controller.txt b/Documentation/cgroups/blkio-controller.txt
index 630879c..ed04fe9 100644
--- a/Documentation/cgroups/blkio-controller.txt
+++ b/Documentation/cgroups/blkio-controller.txt
@@ -77,7 +77,6 @@ Details of cgroup files
=======================
- blkio.weight
- Specifies per cgroup weight.
-
Currently allowed range of weights is from 100 to 1000.

- blkio.time
@@ -92,6 +91,49 @@ Details of cgroup files
third field specifies the number of sectors transferred by the
group to/from the device.

+- blkio.io_service_bytes
+ - Number of bytes transferred to/from the disk by the group. These
+ are further divided by the type of operation - read or write, sync
+ or async. First two fields specify the major and minor number of the
+ device, third field specifies the operation type and the fourth field
+ specifies the number of bytes.
+
+- blkio.io_serviced
+ - Number of IOs completed to/from the disk by the group. These
+ are further divided by the type of operation - read or write, sync
+ or async. First two fields specify the major and minor number of the
+ device, third field specifies the operation type and the fourth field
+ specifies the number of IOs.
+
+- blkio.io_service_time
+ - Total amount of time between request dispatch and request completion
+ for the IOs done by this cgroup. This is in nanoseconds to make it
+ meaningful for flash devices too. For devices with queue depth of 1,
+ this time represents the actual service time. When queue_depth > 1,
+ that is no longer true as requests may be served out of order. This
+ may cause the service time for a given IO to include the service time
+ of multiple IOs when served out of order which may result in total
+ io_service_time > actual time elapsed. This time is further divided by
+ the type of operation - read or write, sync or async. First two fields
+ specify the major and minor number of the device, third field
+ specifies the operation type and the fourth field specifies the
+ io_service_time in ns.
+
+- blkio.io_wait_time
+ - Total amount of time the IOs for this cgroup spent waiting in the
+ scheduler queues for service. This can be greater than the total time
+ elapsed since it is cumulative io_wait_time for all IOs. It is not a
+ measure of total time the cgroup spent waiting but rather a measure of
+ the wait_time for its individual IOs. For devices with queue_depth > 1
+ this metric does not include the time spent waiting for service once
+ the IO is dispatched to the device but till it actually gets serviced
+ (there might be a time lag here due to re-ordering of requests by the
+ device). This is in nanoseconds to make it meaningful for flash
+ devices too. This time is further divided by the type of operation -
+ read or write, sync or async. First two fields specify the major and
+ minor number of the device, third field specifies the operation type
+ and the fourth field specifies the io_wait_time in ns.
+
- blkio.dequeue
- Debugging aid only enabled if CONFIG_DEBUG_CFQ_IOSCHED=y. This
gives the statistics about how many a times a group was dequeued
@@ -99,6 +141,10 @@ Details of cgroup files
and minor number of the device and third field specifies the number
of times a group was dequeued from a particular device.

+- blkio.reset_stats
+ - Writing an int to this file will result in resetting all the stats
+ for that cgroup.
+
CFQ sysfs tunable
=================
/sys/block/<disk>/queue/iosched/group_isolation
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 5be3981..5849a63 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -17,6 +17,8 @@
#include <linux/err.h>
#include "blk-cgroup.h"

+#define MAX_KEY_LEN 100
+
static DEFINE_SPINLOCK(blkio_list_lock);
static LIST_HEAD(blkio_list);

@@ -55,12 +57,21 @@ struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
}
EXPORT_SYMBOL_GPL(cgroup_to_blkio_cgroup);

-void blkiocg_update_blkio_group_stats(struct blkio_group *blkg,
- unsigned long time)
+void blkio_group_init(struct blkio_group *blkg)
+{
+ spin_lock_init(&blkg->stats_lock);
+}
+EXPORT_SYMBOL_GPL(blkio_group_init);
+
+void blkiocg_update_timeslice_used(struct blkio_group *blkg, unsigned long time)
{
- blkg->time += time;
+ unsigned long flags;
+
+ spin_lock_irqsave(&blkg->stats_lock, flags);
+ blkg->stats.time += time;
+ spin_unlock_irqrestore(&blkg->stats_lock, flags);
}
-EXPORT_SYMBOL_GPL(blkiocg_update_blkio_group_stats);
+EXPORT_SYMBOL_GPL(blkiocg_update_timeslice_used);

void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
struct blkio_group *blkg, void *key, dev_t dev)
@@ -170,13 +181,107 @@ blkiocg_weight_write(struct cgroup *cgroup, struct cftype *cftype, u64 val)
return 0;
}

-#define SHOW_FUNCTION_PER_GROUP(__VAR) \
+static int
+blkiocg_reset_stats(struct cgroup *cgroup, struct cftype *cftype, u64 val)
+{
+ struct blkio_cgroup *blkcg;
+ struct blkio_group *blkg;
+ struct hlist_node *n;
+ struct blkio_group_stats *stats;
+
+ blkcg = cgroup_to_blkio_cgroup(cgroup);
+ spin_lock_irq(&blkcg->lock);
+ hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
+ spin_lock(&blkg->stats_lock);
+ stats = &blkg->stats;
+ memset(stats, 0, sizeof(struct blkio_group_stats));
+ spin_unlock(&blkg->stats_lock);
+ }
+ spin_unlock_irq(&blkcg->lock);
+ return 0;
+}
+
+static void blkio_get_key_name(enum stat_sub_type type, dev_t dev, char *str,
+ int chars_left, bool diskname_only)
+{
+ snprintf(str, chars_left, "%d:%d", MAJOR(dev), MINOR(dev));
+ chars_left -= strlen(str);
+ if (chars_left <= 0) {
+ printk(KERN_WARNING
+ "Possibly incorrect cgroup stat display format");
+ return;
+ }
+ if (diskname_only)
+ return;
+ switch (type) {
+ case BLKIO_STAT_READ:
+ strlcat(str, " Read", chars_left);
+ break;
+ case BLKIO_STAT_WRITE:
+ strlcat(str, " Write", chars_left);
+ break;
+ case BLKIO_STAT_SYNC:
+ strlcat(str, " Sync", chars_left);
+ break;
+ case BLKIO_STAT_ASYNC:
+ strlcat(str, " Async", chars_left);
+ break;
+ case BLKIO_STAT_TOTAL:
+ strlcat(str, " Total", chars_left);
+ break;
+ default:
+ strlcat(str, " Invalid", chars_left);
+ }
+}
+
+static uint64_t blkio_fill_stat(char *str, int chars_left, uint64_t val,
+ struct cgroup_map_cb *cb, dev_t dev)
+{
+ blkio_get_key_name(0, dev, str, chars_left, true);
+ cb->fill(cb, str, val);
+ return val;
+}
+
+/* This should be called with blkg->stats_lock held */
+static uint64_t blkio_get_stat(struct blkio_group *blkg,
+ struct cgroup_map_cb *cb, dev_t dev, enum stat_type type)
+{
+ uint64_t disk_total;
+ char key_str[MAX_KEY_LEN];
+ enum stat_sub_type sub_type;
+
+ if (type == BLKIO_STAT_TIME)
+ return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
+ blkg->stats.time, cb, dev);
+ if (type == BLKIO_STAT_SECTORS)
+ return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
+ blkg->stats.sectors, cb, dev);
+#ifdef CONFIG_DEBUG_BLK_CGROUP
+ if (type == BLKIO_STAT_DEQUEUE)
+ return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
+ blkg->stats.dequeue, cb, dev);
+#endif
+
+ for (sub_type = BLKIO_STAT_READ; sub_type < BLKIO_STAT_TOTAL;
+ sub_type++) {
+ blkio_get_key_name(sub_type, dev, key_str, MAX_KEY_LEN, false);
+ cb->fill(cb, key_str, blkg->stats.stat_arr[type][sub_type]);
+ }
+ disk_total = blkg->stats.stat_arr[type][BLKIO_STAT_READ] +
+ blkg->stats.stat_arr[type][BLKIO_STAT_WRITE];
+ blkio_get_key_name(BLKIO_STAT_TOTAL, dev, key_str, MAX_KEY_LEN, false);
+ cb->fill(cb, key_str, disk_total);
+ return disk_total;
+}
+
+#define SHOW_FUNCTION_PER_GROUP(__VAR, type, show_total) \
static int blkiocg_##__VAR##_read(struct cgroup *cgroup, \
- struct cftype *cftype, struct seq_file *m) \
+ struct cftype *cftype, struct cgroup_map_cb *cb) \
{ \
struct blkio_cgroup *blkcg; \
struct blkio_group *blkg; \
struct hlist_node *n; \
+ uint64_t cgroup_total = 0; \
\
if (!cgroup_lock_live_group(cgroup)) \
return -ENODEV; \
@@ -184,19 +289,28 @@ static int blkiocg_##__VAR##_read(struct cgroup *cgroup, \
blkcg = cgroup_to_blkio_cgroup(cgroup); \
rcu_read_lock(); \
hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {\
- if (blkg->dev) \
- seq_printf(m, "%u:%u %lu\n", MAJOR(blkg->dev), \
- MINOR(blkg->dev), blkg->__VAR); \
+ if (blkg->dev) { \
+ spin_lock_irq(&blkg->stats_lock); \
+ cgroup_total += blkio_get_stat(blkg, cb, \
+ blkg->dev, type); \
+ spin_unlock_irq(&blkg->stats_lock); \
+ } \
} \
+ if (show_total) \
+ cb->fill(cb, "Total", cgroup_total); \
rcu_read_unlock(); \
cgroup_unlock(); \
return 0; \
}

-SHOW_FUNCTION_PER_GROUP(time);
-SHOW_FUNCTION_PER_GROUP(sectors);
+SHOW_FUNCTION_PER_GROUP(time, BLKIO_STAT_TIME, 0);
+SHOW_FUNCTION_PER_GROUP(sectors, BLKIO_STAT_SECTORS, 0);
+SHOW_FUNCTION_PER_GROUP(io_service_bytes, BLKIO_STAT_SERVICE_BYTES, 1);
+SHOW_FUNCTION_PER_GROUP(io_serviced, BLKIO_STAT_SERVICED, 1);
+SHOW_FUNCTION_PER_GROUP(io_service_time, BLKIO_STAT_SERVICE_TIME, 1);
+SHOW_FUNCTION_PER_GROUP(io_wait_time, BLKIO_STAT_WAIT_TIME, 1);
#ifdef CONFIG_DEBUG_BLK_CGROUP
-SHOW_FUNCTION_PER_GROUP(dequeue);
+SHOW_FUNCTION_PER_GROUP(dequeue, BLKIO_STAT_DEQUEUE, 0);
#endif
#undef SHOW_FUNCTION_PER_GROUP

@@ -204,7 +318,7 @@ SHOW_FUNCTION_PER_GROUP(dequeue);
void blkiocg_update_blkio_group_dequeue_stats(struct blkio_group *blkg,
unsigned long dequeue)
{
- blkg->dequeue += dequeue;
+ blkg->stats.dequeue += dequeue;
}
EXPORT_SYMBOL_GPL(blkiocg_update_blkio_group_dequeue_stats);
#endif
@@ -217,16 +331,36 @@ struct cftype blkio_files[] = {
},
{
.name = "time",
- .read_seq_string = blkiocg_time_read,
+ .read_map = blkiocg_time_read,
},
{
.name = "sectors",
- .read_seq_string = blkiocg_sectors_read,
+ .read_map = blkiocg_sectors_read,
+ },
+ {
+ .name = "io_service_bytes",
+ .read_map = blkiocg_io_service_bytes_read,
+ },
+ {
+ .name = "io_serviced",
+ .read_map = blkiocg_io_serviced_read,
+ },
+ {
+ .name = "io_service_time",
+ .read_map = blkiocg_io_service_time_read,
+ },
+ {
+ .name = "io_wait_time",
+ .read_map = blkiocg_io_wait_time_read,
+ },
+ {
+ .name = "reset_stats",
+ .write_u64 = blkiocg_reset_stats,
},
#ifdef CONFIG_DEBUG_BLK_CGROUP
{
.name = "dequeue",
- .read_seq_string = blkiocg_dequeue_read,
+ .read_map = blkiocg_dequeue_read,
},
#endif
};
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index fe44517..a4bc4bb 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -23,6 +23,33 @@ extern struct cgroup_subsys blkio_subsys;
#define blkio_subsys_id blkio_subsys.subsys_id
#endif

+enum stat_type {
+ /* Total time spent (in ns) between request dispatch to the driver and
+ * request completion for IOs doen by this cgroup. This may not be
+ * accurate when NCQ is turned on. */
+ BLKIO_STAT_SERVICE_TIME = 0,
+ /* Total bytes transferred */
+ BLKIO_STAT_SERVICE_BYTES,
+ /* Total IOs serviced, post merge */
+ BLKIO_STAT_SERVICED,
+ /* Total time spent waiting in scheduler queue in ns */
+ BLKIO_STAT_WAIT_TIME,
+ /* All the single valued stats go below this */
+ BLKIO_STAT_TIME,
+ BLKIO_STAT_SECTORS,
+#ifdef CONFIG_DEBUG_BLK_CGROUP
+ BLKIO_STAT_DEQUEUE
+#endif
+};
+
+enum stat_sub_type {
+ BLKIO_STAT_READ = 0,
+ BLKIO_STAT_WRITE,
+ BLKIO_STAT_SYNC,
+ BLKIO_STAT_ASYNC,
+ BLKIO_STAT_TOTAL
+};
+
struct blkio_cgroup {
struct cgroup_subsys_state css;
unsigned int weight;
@@ -30,6 +57,17 @@ struct blkio_cgroup {
struct hlist_head blkg_list;
};

+struct blkio_group_stats {
+ /* total disk time and nr sectors dispatched by this group */
+ uint64_t time;
+ uint64_t sectors;
+ uint64_t stat_arr[BLKIO_STAT_WAIT_TIME + 1][BLKIO_STAT_TOTAL];
+#ifdef CONFIG_DEBUG_BLK_CGROUP
+ /* How many times this group has been removed from service tree */
+ unsigned long dequeue;
+#endif
+};
+
struct blkio_group {
/* An rcu protected unique identifier for the group */
void *key;
@@ -38,15 +76,13 @@ struct blkio_group {
#ifdef CONFIG_DEBUG_BLK_CGROUP
/* Store cgroup path */
char path[128];
- /* How many times this group has been removed from service tree */
- unsigned long dequeue;
#endif
/* The device MKDEV(major, minor), this group has been created for */
- dev_t dev;
+ dev_t dev;

- /* total disk time and nr sectors dispatched by this group */
- unsigned long time;
- unsigned long sectors;
+ /* Need to serialize the stats in the case of reset/update */
+ spinlock_t stats_lock;
+ struct blkio_group_stats stats;
};

typedef void (blkio_unlink_group_fn) (void *key, struct blkio_group *blkg);
@@ -105,24 +141,24 @@ extern void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
extern int blkiocg_del_blkio_group(struct blkio_group *blkg);
extern struct blkio_group *blkiocg_lookup_group(struct blkio_cgroup *blkcg,
void *key);
-void blkiocg_update_blkio_group_stats(struct blkio_group *blkg,
- unsigned long time);
+void blkio_group_init(struct blkio_group *blkg);
+void blkiocg_update_timeslice_used(struct blkio_group *blkg,
+ unsigned long time);
#else
struct cgroup;
static inline struct blkio_cgroup *
cgroup_to_blkio_cgroup(struct cgroup *cgroup) { return NULL; }

+static inline void blkio_group_init(struct blkio_group *blkg) {}
static inline void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
- struct blkio_group *blkg, void *key, dev_t dev)
-{
-}
+ struct blkio_group *blkg, void *key, dev_t dev) {}

static inline int
blkiocg_del_blkio_group(struct blkio_group *blkg) { return 0; }

static inline struct blkio_group *
blkiocg_lookup_group(struct blkio_cgroup *blkcg, void *key) { return NULL; }
-static inline void blkiocg_update_blkio_group_stats(struct blkio_group *blkg,
+static inline void blkiocg_update_timeslice_used(struct blkio_group *blkg,
unsigned long time) {}
#endif
#endif /* _BLK_CGROUP_H */
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index c18e348..cf11548 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -914,7 +914,7 @@ static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,

cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
st->min_vdisktime);
- blkiocg_update_blkio_group_stats(&cfqg->blkg, used_sl);
+ blkiocg_update_timeslice_used(&cfqg->blkg, used_sl);
}

#ifdef CONFIG_CFQ_GROUP_IOSCHED
@@ -954,6 +954,7 @@ cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
for_each_cfqg_st(cfqg, i, j, st)
*st = CFQ_RB_ROOT;
RB_CLEAR_NODE(&cfqg->rb_node);
+ blkio_group_init(&cfqg->blkg);

/*
* Take the initial reference that will be released on destroy

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