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Message-Id: <1299619256-12661-6-git-send-email-teravest@google.com>
Date:	Tue,  8 Mar 2011 13:20:55 -0800
From:	Justin TerAvest <teravest@...gle.com>
To:	m-ikeda@...jp.nec.com, jaxboe@...ionio.com, vgoyal@...hat.com
Cc:	linux-kernel@...r.kernel.org, ryov@...inux.co.jp,
	taka@...inux.co.jp, kamezawa.hiroyu@...fujitsu.com,
	righi.andrea@...il.com, guijianfeng@...fujitsu.com,
	balbir@...ux.vnet.ibm.com, ctalbott@...gle.com, nauman@...gle.com,
	mrubin@...gle.com, Justin TerAvest <teravest@...gle.com>
Subject: [PATCH 5/6] Add stat for per cgroup writeout done by flusher.

Tracking for buffered writes can detect when traffic comes from a
flusher thread, as opposed to directly from an application. This adds a
statistic to track I/O traffic from flusher threads.

This helps determine whether a flusher thread is being unfair to a
particular cgroup, and if cgroup-based isolation of writeback behavior
is useful.

Signed-off-by: Justin TerAvest <teravest@...gle.com>
---
 block/blk-cgroup.c        |   18 ++++++++++++++++-
 block/blk-cgroup.h        |    9 ++++++-
 block/cfq-iosched.c       |   47 ++++++++++++++++++++++++++------------------
 block/cfq.h               |    6 +++-
 include/linux/blk_types.h |    2 +
 5 files changed, 58 insertions(+), 24 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 0f147aa..93d2a08 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -410,7 +410,8 @@ void blkiocg_update_dispatch_stats(struct blkio_group *blkg,
 EXPORT_SYMBOL_GPL(blkiocg_update_dispatch_stats);
 
 void blkiocg_update_completion_stats(struct blkio_group *blkg,
-	uint64_t start_time, uint64_t io_start_time, bool direction, bool sync)
+	uint64_t start_time, uint64_t io_start_time, bool direction, bool sync,
+	bool out_of_ctx)
 {
 	struct blkio_group_stats *stats;
 	unsigned long flags;
@@ -424,6 +425,8 @@ void blkiocg_update_completion_stats(struct blkio_group *blkg,
 	if (time_after64(io_start_time, start_time))
 		blkio_add_stat(stats->stat_arr[BLKIO_STAT_WAIT_TIME],
 				io_start_time - start_time, direction, sync);
+	if (out_of_ctx)
+		blkg->stats.oo_ctx_io_count++;
 	spin_unlock_irqrestore(&blkg->stats_lock, flags);
 }
 EXPORT_SYMBOL_GPL(blkiocg_update_completion_stats);
@@ -615,6 +618,9 @@ static uint64_t blkio_get_stat(struct blkio_group *blkg,
 		return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
 					blkg->stats.sectors, cb, dev);
 #ifdef CONFIG_DEBUG_BLK_CGROUP
+	if (type == BLKIO_STAT_OO_CTX_IO_COUNT)
+		return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
+					blkg->stats.oo_ctx_io_count, cb, dev);
 	if (type == BLKIO_STAT_AVG_QUEUE_SIZE) {
 		uint64_t sum = blkg->stats.avg_queue_size_sum;
 		uint64_t samples = blkg->stats.avg_queue_size_samples;
@@ -1151,6 +1157,10 @@ static int blkiocg_file_read_map(struct cgroup *cgrp, struct cftype *cft,
 		case BLKIO_PROP_empty_time:
 			return blkio_read_blkg_stats(blkcg, cft, cb,
 						BLKIO_STAT_EMPTY_TIME, 0);
+		case BLKIO_PROP_oo_ctx_io_count:
+			return blkio_read_blkg_stats(blkcg, cft, cb,
+						BLKIO_STAT_OO_CTX_IO_COUNT, 0);
+
 #endif
 		default:
 			BUG();
@@ -1405,6 +1415,12 @@ struct cftype blkio_files[] = {
 				BLKIO_PROP_dequeue),
 		.read_map = blkiocg_file_read_map,
 	},
+	{
+		.name = "oo_ctx_io_count",
+		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
+				BLKIO_PROP_oo_ctx_io_count),
+		.read_map = blkiocg_file_read_map,
+	},
 #endif
 };
 
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index ea4861b..bdb1b73 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -50,6 +50,7 @@ enum stat_type {
 	BLKIO_STAT_TIME,
 	BLKIO_STAT_SECTORS,
 #ifdef CONFIG_DEBUG_BLK_CGROUP
+	BLKIO_STAT_OO_CTX_IO_COUNT,
 	BLKIO_STAT_AVG_QUEUE_SIZE,
 	BLKIO_STAT_IDLE_TIME,
 	BLKIO_STAT_EMPTY_TIME,
@@ -90,6 +91,7 @@ enum blkcg_file_name_prop {
 	BLKIO_PROP_idle_time,
 	BLKIO_PROP_empty_time,
 	BLKIO_PROP_dequeue,
+	BLKIO_PROP_oo_ctx_io_count,
 };
 
 /* cgroup files owned by throttle policy */
@@ -114,6 +116,8 @@ struct blkio_group_stats {
 	/* total disk time and nr sectors dispatched by this group */
 	uint64_t time;
 	uint64_t sectors;
+	/* Number of IOs sumbitted out of process context */
+	uint64_t oo_ctx_io_count;
 	uint64_t stat_arr[BLKIO_STAT_QUEUED + 1][BLKIO_STAT_TOTAL];
 #ifdef CONFIG_DEBUG_BLK_CGROUP
 	/* Sum of number of IOs queued across all samples */
@@ -297,7 +301,8 @@ void blkiocg_update_timeslice_used(struct blkio_group *blkg,
 void blkiocg_update_dispatch_stats(struct blkio_group *blkg, uint64_t bytes,
 						bool direction, bool sync);
 void blkiocg_update_completion_stats(struct blkio_group *blkg,
-	uint64_t start_time, uint64_t io_start_time, bool direction, bool sync);
+	uint64_t start_time, uint64_t io_start_time, bool direction, bool sync,
+	bool out_of_ctx);
 void blkiocg_update_io_merged_stats(struct blkio_group *blkg, bool direction,
 					bool sync);
 void blkiocg_update_io_add_stats(struct blkio_group *blkg,
@@ -324,7 +329,7 @@ static inline void blkiocg_update_dispatch_stats(struct blkio_group *blkg,
 				uint64_t bytes, bool direction, bool sync) {}
 static inline void blkiocg_update_completion_stats(struct blkio_group *blkg,
 		uint64_t start_time, uint64_t io_start_time, bool direction,
-		bool sync) {}
+						bool sync, bool out_of_ctx) {}
 static inline void blkiocg_update_io_merged_stats(struct blkio_group *blkg,
 						bool direction, bool sync) {}
 static inline void blkiocg_update_io_add_stats(struct blkio_group *blkg,
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index ef01dd8..fa5a34d 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -305,7 +305,7 @@ struct cfq_data {
 
 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);
 static struct cfq_group *cfq_get_cfqg_bio(struct cfq_data *cfqd,
-				   struct bio *bio, int create);
+			struct bio *bio, int *is_oo_ctx, int create);
 static struct cfq_queue **
 cfq_async_queue_prio(struct cfq_group *cfqg, int ioprio_class, int ioprio);
 
@@ -443,8 +443,8 @@ static inline int cfq_group_busy_queues_wl(enum wl_prio_t wl,
 }
 
 static void cfq_dispatch_insert(struct request_queue *, struct request *);
-static struct cfq_queue *cfq_get_queue(struct cfq_data *, struct bio*, bool,
-				       struct io_context *, gfp_t);
+static struct cfq_queue *cfq_get_queue(struct cfq_data *, struct bio*,
+		int *is_oo_ctx, bool, struct io_context *, gfp_t);
 static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
 						struct io_context *);
 static void cfq_put_async_queues(struct cfq_group *cfqg);
@@ -478,7 +478,7 @@ static struct cfq_queue *cic_bio_to_cfqq(struct cfq_data *cfqd,
 		 * async bio tracking is enabled and we are not caching
 		 * async queue pointer in cic.
 		 */
-		cfqg = cfq_get_cfqg_bio(cfqd, bio, 0);
+		cfqg = cfq_get_cfqg_bio(cfqd, bio, NULL, 0);
 		if (!cfqg) {
 			/*
 			 * May be this is first rq/bio and io group has not
@@ -1146,17 +1146,21 @@ done:
  * create the cfq group if it does not exist. request_queue lock must be held.
  */
 static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, struct page *page,
-				      int create)
+				      int *is_oo_ctx, int create)
 {
-	struct cgroup *cgroup;
+	struct cgroup *cgroup, *tracked_cgroup;
 	struct cfq_group *cfqg = NULL;
 
 	rcu_read_lock();
 
-	if (!page)
-		cgroup = task_cgroup(current, blkio_subsys_id);
-	else
-		cgroup = get_cgroup_from_page(page);
+	cgroup = task_cgroup(current, blkio_subsys_id);
+	if (page) {
+		tracked_cgroup = get_cgroup_from_page(page);
+		if (is_oo_ctx)
+			*is_oo_ctx = cgroup && tracked_cgroup &&
+				tracked_cgroup != cgroup;
+		cgroup = tracked_cgroup;
+	}
 
 	if (!cgroup) {
 		cfqg = &cfqd->root_group;
@@ -1177,8 +1181,8 @@ static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg)
 	return cfqg;
 }
 
-struct cfq_group *cfq_get_cfqg_bio(struct cfq_data *cfqd,
-					struct bio *bio, int create)
+struct cfq_group *cfq_get_cfqg_bio(struct cfq_data *cfqd, struct bio *bio,
+					int *is_oo_ctx, int create)
 {
 	struct page *page = NULL;
 
@@ -1200,7 +1204,7 @@ struct cfq_group *cfq_get_cfqg_bio(struct cfq_data *cfqd,
 #endif
 
 sync:
-	return cfq_get_cfqg(cfqd, page, create);
+	return cfq_get_cfqg(cfqd, page, is_oo_ctx, create);
 }
 
 static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
@@ -1281,7 +1285,7 @@ void cfq_unlink_blkio_group(void *key, struct blkio_group *blkg)
 
 #else /* GROUP_IOSCHED */
 static struct cfq_group *cfq_get_cfqg_bio(struct cfq_data *cfqd,
-					  struct bio *bio, int create)
+			struct bio *bio, int *is_oo_ctx, int create)
 {
 	return &cfqd->root_group;
 }
@@ -3095,14 +3099,14 @@ cfq_async_queue_prio(struct cfq_group *cfqg, int ioprio_class, int ioprio)
 }
 
 static struct cfq_queue *
-cfq_get_queue(struct cfq_data *cfqd, struct bio *bio, bool is_sync,
-	      struct io_context *ioc, gfp_t gfp_mask)
+cfq_get_queue(struct cfq_data *cfqd, struct bio *bio, int *is_oo_ctx,
+	      bool is_sync, struct io_context *ioc, gfp_t gfp_mask)
 {
 	const int ioprio = task_ioprio(ioc);
 	const int ioprio_class = task_ioprio_class(ioc);
 	struct cfq_queue **async_cfqq = NULL;
 	struct cfq_queue *cfqq = NULL;
-	struct cfq_group *cfqg = cfq_get_cfqg_bio(cfqd, bio, 1);
+	struct cfq_group *cfqg = cfq_get_cfqg_bio(cfqd, bio, is_oo_ctx, 1);
 
 	if (!is_sync) {
 		async_cfqq = cfq_async_queue_prio(cfqg, ioprio_class,
@@ -3625,7 +3629,8 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
 	(RQ_CFQG(rq))->dispatched--;
 	cfq_blkiocg_update_completion_stats(&cfqq->cfqg->blkg,
 			rq_start_time_ns(rq), rq_io_start_time_ns(rq),
-			rq_data_dir(rq), rq_is_sync(rq));
+			rq_data_dir(rq), rq_is_sync(rq),
+			rq->cmd_flags & REQ_OUT_OF_CTX);
 
 	cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]--;
 
@@ -3813,6 +3818,7 @@ cfq_set_request(struct request_queue *q, struct request *rq, struct bio *bio,
 	const bool is_sync = rq_is_sync(rq);
 	struct cfq_queue *cfqq;
 	unsigned long flags;
+	int is_oo_ctx = 0;
 
 	might_sleep_if(gfp_mask & __GFP_WAIT);
 
@@ -3826,8 +3832,11 @@ cfq_set_request(struct request_queue *q, struct request *rq, struct bio *bio,
 new_queue:
 	cfqq = cic_to_cfqq(cic, is_sync);
 	if (!cfqq || cfqq == &cfqd->oom_cfqq) {
-		cfqq = cfq_get_queue(cfqd, bio, is_sync, cic->ioc, gfp_mask);
+		cfqq = cfq_get_queue(cfqd, bio, &is_oo_ctx, is_sync, cic->ioc,
+					gfp_mask);
 		cic_set_cfqq(cic, cfqq, is_sync);
+		if (is_oo_ctx)
+			rq->cmd_flags |= REQ_OUT_OF_CTX;
 	} else {
 		/*
 		 * If the queue was seeky for too long, break it apart.
diff --git a/block/cfq.h b/block/cfq.h
index 54a6d90..23410eb 100644
--- a/block/cfq.h
+++ b/block/cfq.h
@@ -61,10 +61,12 @@ static inline void cfq_blkiocg_update_dispatch_stats(struct blkio_group *blkg,
 	blkiocg_update_dispatch_stats(blkg, bytes, direction, sync);
 }
 
-static inline void cfq_blkiocg_update_completion_stats(struct blkio_group *blkg, uint64_t start_time, uint64_t io_start_time, bool direction, bool sync)
+static inline void cfq_blkiocg_update_completion_stats(struct blkio_group *blkg,
+				uint64_t start_time, uint64_t io_start_time,
+				bool direction, bool sync, bool out_of_ctx)
 {
 	blkiocg_update_completion_stats(blkg, start_time, io_start_time,
-				direction, sync);
+				direction, sync, out_of_ctx);
 }
 
 static inline void cfq_blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 46ad519..eb25b06 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -151,6 +151,7 @@ enum rq_flag_bits {
 	__REQ_IO_STAT,		/* account I/O stat */
 	__REQ_MIXED_MERGE,	/* merge of different types, fail separately */
 	__REQ_SECURE,		/* secure discard (used with __REQ_DISCARD) */
+	__REQ_OUT_OF_CTX,	/* request submitted out of process context */
 	__REQ_NR_BITS,		/* stops here */
 };
 
@@ -191,5 +192,6 @@ enum rq_flag_bits {
 #define REQ_IO_STAT		(1 << __REQ_IO_STAT)
 #define REQ_MIXED_MERGE		(1 << __REQ_MIXED_MERGE)
 #define REQ_SECURE		(1 << __REQ_SECURE)
+#define REQ_OUT_OF_CTX		(1 << __REQ_OUT_OF_CTX)
 
 #endif /* __LINUX_BLK_TYPES_H */
-- 
1.7.3.1

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