5 files changed, 53 insertions, 1 deletions

diff --git a/block/Kconfig b/block/Kconfig
index 6ba1a8e3388b..e20fbde0875c 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -90,6 +90,15 @@ config BLK_CGROUP
         control disk bandwidth allocation (proportional time slice allocation)
         to such task groups.
 
+config DEBUG_BLK_CGROUP
+        bool
+        depends on BLK_CGROUP
+        default n
+        ---help---
+        Enable some debugging help. Currently it stores the cgroup path
+        in the blk group which can be used by cfq for tracing various
+        group related activity.
+
 endif # BLOCK
 
 config BLOCK_COMPAT
diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
index fa95fa770570..b71abfb0d726 100644
--- a/block/Kconfig.iosched
+++ b/block/Kconfig.iosched
@@ -40,6 +40,15 @@ config CFQ_GROUP_IOSCHED
         ---help---
           Enable group IO scheduling in CFQ.
 
+config DEBUG_CFQ_IOSCHED
+        bool "Debug CFQ Scheduling"
+        depends on CFQ_GROUP_IOSCHED
+        select DEBUG_BLK_CGROUP
+        default n
+        ---help---
+          Enable CFQ IO scheduling debugging in CFQ. Currently it makes
+          blktrace output more verbose.
+
 choice
         prompt "Default I/O scheduler"
         default DEFAULT_CFQ
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 0426ab692fd5..6bc99a3865b0 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -33,6 +33,10 @@ void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
         blkg->blkcg_id = css_id(&blkcg->css);
         hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
         spin_unlock_irqrestore(&blkcg->lock, flags);
+#ifdef CONFIG_DEBUG_BLK_CGROUP
+        /* Need to take css reference ? */
+        cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path));
+#endif
 }
 
 static void __blkiocg_del_blkio_group(struct blkio_group *blkg)
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index cd50a2f8733e..3573199b298b 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -27,12 +27,25 @@ struct blkio_group {
         void *key;
         struct hlist_node blkcg_node;
         unsigned short blkcg_id;
+#ifdef CONFIG_DEBUG_BLK_CGROUP
+        /* Store cgroup path */
+        char path[128];
+#endif
 };
 
 #define BLKIO_WEIGHT_MIN        100
 #define BLKIO_WEIGHT_MAX        1000
 #define BLKIO_WEIGHT_DEFAULT    500
 
+#ifdef CONFIG_DEBUG_BLK_CGROUP
+static inline char *blkg_path(struct blkio_group *blkg)
+{
+        return blkg->path;
+}
+#else
+static inline char *blkg_path(struct blkio_group *blkg) { return NULL; }
+#endif
+
 #ifdef CONFIG_BLK_CGROUP
 extern struct blkio_cgroup blkio_root_cgroup;
 extern struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup);
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 8bc31a50a57f..662d4e55b3c2 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -341,8 +341,21 @@ CFQ_CFQQ_FNS(coop);
 CFQ_CFQQ_FNS(deep);
 #undef CFQ_CFQQ_FNS
 
+#ifdef CONFIG_DEBUG_CFQ_IOSCHED
+#define cfq_log_cfqq(cfqd, cfqq, fmt, args...)  \
+        blk_add_trace_msg((cfqd)->queue, "cfq%d%c %s " fmt, (cfqq)->pid, \
+                        cfq_cfqq_sync((cfqq)) ? 'S' : 'A', \
+                        blkg_path(&(cfqq)->cfqg->blkg), ##args);
+
+#define cfq_log_cfqg(cfqd, cfqg, fmt, args...)                          \
+        blk_add_trace_msg((cfqd)->queue, "%s " fmt,                     \
+                                blkg_path(&(cfqg)->blkg), ##args);      \
+
+#else
 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...)  \
         blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
+#define cfq_log_cfqg(cfqd, cfqg, fmt, args...)          do {} while (0);
+#endif
 #define cfq_log(cfqd, fmt, args...)     \
         blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
 
@@ -832,6 +845,7 @@ cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
         if (cfqg->nr_cfqq)
                 return;
 
+        cfq_log_cfqg(cfqd, cfqg, "del_from_rr group");
         cfqg->on_st = false;
         cfqd->nr_groups--;
         st->total_weight -= cfqg->weight;
@@ -889,6 +903,9 @@ static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
                 cfqg->saved_serving_prio = cfqd->serving_prio;
         } else
                 cfqg->saved_workload_slice = 0;
+
+        cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
+                                        st->min_vdisktime);
 }
 
 #ifdef CONFIG_CFQ_GROUP_IOSCHED
@@ -3102,7 +3119,7 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
         unsigned long now;
 
         now = jiffies;
-        cfq_log_cfqq(cfqd, cfqq, "complete");
+        cfq_log_cfqq(cfqd, cfqq, "complete rqnoidle %d", !!rq_noidle(rq));
 
         cfq_update_hw_tag(cfqd);