Re: [PATCH 18/19] io-controller: Debug hierarchical IO scheduling

Gui Jianfeng
2009-06-19T01:42:49Z

Vivek Goyal wrote:
> o Littile debugging aid for hierarchical IO scheduling.
>
> o Enabled under CONFIG_DEBUG_GROUP_IOSCHED
>
> o Currently it outputs more debug messages in blktrace output which helps
> a great deal in debugging in hierarchical setup. It also creates additional
> cgroup interfaces io.disk_queue and io.disk_dequeue to output some more
> debugging data.
>
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
> ---
> block/Kconfig.iosched | 10 ++-
> block/as-iosched.c | 50 ++++++---
> block/elevator-fq.c | 285 ++++++++++++++++++++++++++++++++++++++++++++++++-
> block/elevator-fq.h | 26 +++++
> 4 files changed, 347 insertions(+), 24 deletions(-)
>
> diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
> index 0677099..79f188c 100644
> --- a/block/Kconfig.iosched
> +++ b/block/Kconfig.iosched
> @@ -140,6 +140,14 @@ config TRACK_ASYNC_CONTEXT
> request, original owner of the bio is decided by using io tracking
> patches otherwise we continue to attribute the request to the
> submitting thread.
> -endmenu
>
> +config DEBUG_GROUP_IOSCHED
> + bool "Debug Hierarchical Scheduling support"
> + depends on CGROUPS && GROUP_IOSCHED
> + default n
> + ---help---
> + Enable some debugging hooks for hierarchical scheduling support.
> + Currently it just outputs more information in blktrace output.
> +
> +endmenu
> endif
> diff --git a/block/as-iosched.c b/block/as-iosched.c
> index b0c66e4..735d055 100644
> --- a/block/as-iosched.c
> +++ b/block/as-iosched.c
> @@ -78,6 +78,7 @@ enum anticipation_status {
> };
>
> struct as_queue {
> + struct io_queue *ioq;
> /*
> * requests (as_rq s) are present on both sort_list and fifo_list
> */
> @@ -162,6 +163,17 @@ enum arq_state {
> #define RQ_STATE(rq) ((enum arq_state)(rq)->elevator_private2)
> #define RQ_SET_STATE(rq, state) ((rq)->elevator_private2 = (void *) state)
>
> +#ifdef CONFIG_DEBUG_GROUP_IOSCHED
> +#define as_log_asq(ad, asq, fmt, args...) \
> +{ \
> + blk_add_trace_msg((ad)->q, "as %s " fmt, \
> + ioq_to_io_group((asq)->ioq)->path, ##args); \
> +}
> +#else
> +#define as_log_asq(ad, asq, fmt, args...) \
> + blk_add_trace_msg((ad)->q, "as " fmt, ##args)
> +#endif
> +
> #define as_log(ad, fmt, args...) \
> blk_add_trace_msg((ad)->q, "as " fmt, ##args)
>
> @@ -225,7 +237,7 @@ static void as_save_batch_context(struct as_data *ad, struct as_queue *asq)
> }
>
> out:
> - as_log(ad, "save batch: dir=%c time_left=%d changed_batch=%d"
> + as_log_asq(ad, asq, "save batch: dir=%c time_left=%d changed_batch=%d"
> " new_batch=%d, antic_status=%d",
> ad->batch_data_dir ? 'R' : 'W',
> asq->current_batch_time_left,
> @@ -247,8 +259,8 @@ static void as_restore_batch_context(struct as_data *ad, struct as_queue *asq)
> asq->current_batch_time_left;
> /* restore asq batch_data_dir info */
> ad->batch_data_dir = asq->saved_batch_data_dir;
> - as_log(ad, "restore batch: dir=%c time=%d reads_q=%d writes_q=%d"
> - " ad->antic_status=%d",
> + as_log_asq(ad, asq, "restore batch: dir=%c time=%d reads_q=%d"
> + " writes_q=%d ad->antic_status=%d",
> ad->batch_data_dir ? 'R' : 'W',
> asq->current_batch_time_left,
> asq->nr_queued[1], asq->nr_queued[0],
> @@ -277,8 +289,8 @@ static int as_expire_ioq(struct request_queue *q, void *sched_queue,
> int status = ad->antic_status;
> struct as_queue *asq = sched_queue;
>
> - as_log(ad, "as_expire_ioq slice_expired=%d, force=%d", slice_expired,
> - force);
> + as_log_asq(ad, asq, "as_expire_ioq slice_expired=%d, force=%d",
> + slice_expired, force);
>
> /* Forced expiry. We don't have a choice */
> if (force) {
> @@ -1019,9 +1031,10 @@ static void update_write_batch(struct as_data *ad, struct request *rq)
> if (write_time < 0)
> write_time = 0;
>
> - as_log(ad, "upd write: write_time=%d batch=%d write_batch_idled=%d"
> - " current_write_count=%d", write_time, batch,
> - asq->write_batch_idled, asq->current_write_count);
> + as_log_asq(ad, asq, "upd write: write_time=%d batch=%d"
> + " write_batch_idled=%d current_write_count=%d",
> + write_time, batch, asq->write_batch_idled,
> + asq->current_write_count);
>
> if (write_time > batch && !asq->write_batch_idled) {
> if (write_time > batch * 3)
> @@ -1038,7 +1051,7 @@ static void update_write_batch(struct as_data *ad, struct request *rq)
> if (asq->write_batch_count < 1)
> asq->write_batch_count = 1;
>
> - as_log(ad, "upd write count=%d", asq->write_batch_count);
> + as_log_asq(ad, asq, "upd write count=%d", asq->write_batch_count);
> }
>
> /*
> @@ -1057,7 +1070,7 @@ static void as_completed_request(struct request_queue *q, struct request *rq)
> goto out;
> }
>
> - as_log(ad, "complete: reads_q=%d writes_q=%d changed_batch=%d"
> + as_log_asq(ad, asq, "complete: reads_q=%d writes_q=%d changed_batch=%d"
> " new_batch=%d switch_queue=%d, dir=%c",
> asq->nr_queued[1], asq->nr_queued[0], ad->changed_batch,
> ad->new_batch, ad->switch_queue,
> @@ -1251,7 +1264,7 @@ static void as_move_to_dispatch(struct as_data *ad, struct request *rq)
> if (RQ_IOC(rq) && RQ_IOC(rq)->aic)
> atomic_inc(&RQ_IOC(rq)->aic->nr_dispatched);
> ad->nr_dispatched++;
> - as_log(ad, "dispatch req dir=%c nr_dispatched = %d",
> + as_log_asq(ad, asq, "dispatch req dir=%c nr_dispatched = %d",
> data_dir ? 'R' : 'W', ad->nr_dispatched);
> }
>
> @@ -1300,7 +1313,7 @@ static int as_dispatch_request(struct request_queue *q, int force)
> }
> asq->last_check_fifo[BLK_RW_ASYNC] = jiffies;
>
> - as_log(ad, "forced dispatch");
> + as_log_asq(ad, asq, "forced dispatch");
> return dispatched;
> }
>
> @@ -1314,7 +1327,7 @@ static int as_dispatch_request(struct request_queue *q, int force)
> || ad->antic_status == ANTIC_WAIT_REQ
> || ad->antic_status == ANTIC_WAIT_NEXT
> || ad->changed_batch) {
> - as_log(ad, "no dispatch. read_q=%d, writes_q=%d"
> + as_log_asq(ad, asq, "no dispatch. read_q=%d, writes_q=%d"
> " ad->antic_status=%d, changed_batch=%d,"
> " switch_queue=%d new_batch=%d", asq->nr_queued[1],
> asq->nr_queued[0], ad->antic_status, ad->changed_batch,
> @@ -1333,7 +1346,7 @@ static int as_dispatch_request(struct request_queue *q, int force)
> goto fifo_expired;
>
> if (as_can_anticipate(ad, rq)) {
> - as_log(ad, "can_anticipate = 1");
> + as_log_asq(ad, asq, "can_anticipate = 1");
> as_antic_waitreq(ad);
> return 0;
> }
> @@ -1353,7 +1366,7 @@ static int as_dispatch_request(struct request_queue *q, int force)
> * data direction (read / write)
> */
>
> - as_log(ad, "select a fresh batch and request");
> + as_log_asq(ad, asq, "select a fresh batch and request");
>
> if (reads) {
> BUG_ON(RB_EMPTY_ROOT(&asq->sort_list[BLK_RW_SYNC]));
> @@ -1369,7 +1382,7 @@ static int as_dispatch_request(struct request_queue *q, int force)
> ad->changed_batch = 1;
> }
> ad->batch_data_dir = BLK_RW_SYNC;
> - as_log(ad, "new batch dir is sync");
> + as_log_asq(ad, asq, "new batch dir is sync");
> rq = rq_entry_fifo(asq->fifo_list[BLK_RW_SYNC].next);
> asq->last_check_fifo[ad->batch_data_dir] = jiffies;
> goto dispatch_request;
> @@ -1394,7 +1407,7 @@ dispatch_writes:
> ad->new_batch = 0;
> }
> ad->batch_data_dir = BLK_RW_ASYNC;
> - as_log(ad, "new batch dir is async");
> + as_log_asq(ad, asq, "new batch dir is async");
> asq->current_write_count = asq->write_batch_count;
> asq->write_batch_idled = 0;
> rq = rq_entry_fifo(asq->fifo_list[BLK_RW_ASYNC].next);
> @@ -1457,7 +1470,7 @@ static void as_add_request(struct request_queue *q, struct request *rq)
> rq->elevator_private = as_get_io_context(q->node);
>
> asq->nr_queued[data_dir]++;
> - as_log(ad, "add a %c request read_q=%d write_q=%d",
> + as_log_asq(ad, asq, "add a %c request read_q=%d write_q=%d",
> data_dir ? 'R' : 'W', asq->nr_queued[1],
> asq->nr_queued[0]);
>
> @@ -1616,6 +1629,7 @@ static void *as_alloc_as_queue(struct request_queue *q,
>
> if (asq->write_batch_count < 2)
> asq->write_batch_count = 2;
> + asq->ioq = ioq;
> out:
> return asq;
> }
> diff --git a/block/elevator-fq.c b/block/elevator-fq.c
> index 207664d..207bdf1 100644
> --- a/block/elevator-fq.c
> +++ b/block/elevator-fq.c
> @@ -117,6 +117,126 @@ static inline int iog_deleting(struct io_group *iog)
> return iog->deleting;
> }
>
> +static inline struct io_group *io_entity_to_iog(struct io_entity *entity)
> +{
> + struct io_group *iog = NULL;
> +
> + BUG_ON(entity == NULL);
> + if (entity->my_sched_data != NULL)
> + iog = container_of(entity, struct io_group, entity);
> + return iog;
> +}
> +
> +/* Returns parent group of io group */
> +static inline struct io_group *iog_parent(struct io_group *iog)
> +{
> + struct io_group *piog;
> +
> + if (!iog->entity.sched_data)
> + return NULL;
> +
> + /*
> + * Not following entity->parent pointer as for top level groups
> + * this pointer is NULL.
> + */
> + piog = container_of(iog->entity.sched_data, struct io_group,
> + sched_data);
> + return piog;
> +}
> +
> +#ifdef CONFIG_DEBUG_GROUP_IOSCHED
> +static void io_group_path(struct io_group *iog, char *buf, int buflen)
> +{
> + unsigned short id = iog->iocg_id;
> + struct cgroup_subsys_state *css;
> +
> + rcu_read_lock();
> +
> + if (!id)
> + goto out;
> +
> + css = css_lookup(&io_subsys, id);
> + if (!css)
> + goto out;
> +
> + if (!css_tryget(css))
> + goto out;
> +
> + cgroup_path(css->cgroup, buf, buflen);
> +
> + css_put(css);
> +
> + rcu_read_unlock();
> + return;
> +out:
> + rcu_read_unlock();
> + buf[0] = '\0';
> + return;
> +}
> +
> +/*
> + * An entity has been freshly added to active tree. Either it came from
> + * idle tree or it was not on any of the trees. Do the accounting.
> + */
> +static inline void bfq_account_for_entity_addition(struct io_entity *entity)
> +{
> + struct io_group *iog = io_entity_to_iog(entity);
> +
> + if (iog) {
> + struct elv_fq_data *efqd;
> + char path[128];
> +
> + /*
> + * Keep track of how many times a group has been removed
> + * from active tree because it did not have any active
> + * backlogged ioq under it
> + */

Hi Vivek,

Should the comment here be "added to" rather than "removed from"?

> + iog->queue++;
> + iog->queue_start = jiffies;
> +
> + /* Log group addition event */
> + rcu_read_lock();
> + efqd = rcu_dereference(iog->key);
> + if (efqd) {
> + io_group_path(iog, path, sizeof(path));
> + elv_log(efqd, "add group=%s weight=%ld", path,
> + iog->entity.weight);
> + }
> + rcu_read_unlock();
> + }
> +}
> +
> +/*
> + * An entity got removed from active tree and either went to idle tree or
> + * not is on any of the tree. Do the accouting
> + */
> +static inline void bfq_account_for_entity_deletion(struct io_entity *entity)
> +{
> + struct io_group *iog = io_entity_to_iog(entity);
> +
> + if (iog) {
> + struct elv_fq_data *efqd;
> + char path[128];
> +
> + iog->dequeue++;
> + /* Keep a track of how long group was on active tree */
> + iog->queue_duration += jiffies_to_msecs(jiffies -
> + iog->queue_start);
> + iog->queue_start = 0;
> +
> + /* Log group deletion event */
> + rcu_read_lock();
> + efqd = rcu_dereference(iog->key);
> + if (efqd) {
> + io_group_path(iog, path, sizeof(path));
> + elv_log(efqd, "del group=%s weight=%ld", path,
> + iog->entity.weight);
> + }
> + rcu_read_unlock();
> + }
> +}
> +#endif
> +
> #else /* GROUP_IOSCHED */
> #define for_each_entity(entity) \
> for (; entity != NULL; entity = NULL)
> @@ -139,6 +259,12 @@ static inline int iog_deleting(struct io_group *iog)
> /* In flat mode, root cgroup can't be deleted. */
> return 0;
> }
> +
> +static inline struct io_group *io_entity_to_iog(struct io_entity *entity)
> +{
> + return NULL;
> +}
> +
> #endif
>
> /*
> @@ -572,6 +698,7 @@ static void __bfq_activate_entity(struct io_entity *entity, int add_front)
> {
> struct io_sched_data *sd = entity->sched_data;
> struct io_service_tree *st = io_entity_service_tree(entity);
> + int newly_added = 0;
>
> if (entity == sd->active_entity) {
> BUG_ON(entity->tree != NULL);
> @@ -598,6 +725,7 @@ static void __bfq_activate_entity(struct io_entity *entity, int add_front)
> bfq_idle_extract(st, entity);
> entity->start = bfq_gt(st->vtime, entity->finish) ?
> st->vtime : entity->finish;
> + newly_added = 1;
> } else {
> /*
> * The finish time of the entity may be invalid, and
> @@ -610,6 +738,7 @@ static void __bfq_activate_entity(struct io_entity *entity, int add_front)
>
> BUG_ON(entity->on_st);
> entity->on_st = 1;
> + newly_added = 1;
> }
>
> st = __bfq_entity_update_prio(st, entity);
> @@ -647,6 +776,10 @@ static void __bfq_activate_entity(struct io_entity *entity, int add_front)
> bfq_calc_finish(entity, entity->budget);
> }
> bfq_active_insert(st, entity);
> +#ifdef CONFIG_DEBUG_GROUP_IOSCHED
> + if (newly_added)
> + bfq_account_for_entity_addition(entity);
> +#endif
> }
>
> /**
> @@ -717,6 +850,9 @@ int __bfq_deactivate_entity(struct io_entity *entity, int requeue)
> BUG_ON(sd->active_entity == entity);
> BUG_ON(sd->next_active == entity);
>
> +#ifdef CONFIG_DEBUG_GROUP_IOSCHED
> + bfq_account_for_entity_deletion(entity);
> +#endif
> return ret;
> }
>
> @@ -1209,6 +1345,67 @@ static int io_cgroup_disk_sectors_read(struct cgroup *cgroup,
> return 0;
> }
>
> +#ifdef CONFIG_DEBUG_GROUP_IOSCHED
> +static int io_cgroup_disk_queue_read(struct cgroup *cgroup,
> + struct cftype *cftype, struct seq_file *m)
> +{
> + struct io_cgroup *iocg = NULL;
> + struct io_group *iog = NULL;
> + struct hlist_node *n;
> +
> + if (!cgroup_lock_live_group(cgroup))
> + return -ENODEV;
> +
> + iocg = cgroup_to_io_cgroup(cgroup);
> + spin_lock_irq(&iocg->lock);
> + /* Loop through all the io groups and print statistics */
> + hlist_for_each_entry_rcu(iog, n, &iocg->group_data, group_node) {
> + /*
> + * There might be groups which are not functional and
> + * waiting to be reclaimed upon cgoup deletion.
> + */
> + if (iog->key) {
> + seq_printf(m, "%u %u %lu %lu\n", MAJOR(iog->dev),
> + MINOR(iog->dev), iog->queue,
> + iog->queue_duration);
> + }
> + }
> + spin_unlock_irq(&iocg->lock);
> + cgroup_unlock();
> +
> + return 0;
> +}
> +
> +static int io_cgroup_disk_dequeue_read(struct cgroup *cgroup,
> + struct cftype *cftype, struct seq_file *m)
> +{
> + struct io_cgroup *iocg = NULL;
> + struct io_group *iog = NULL;
> + struct hlist_node *n;
> +
> + if (!cgroup_lock_live_group(cgroup))
> + return -ENODEV;
> +
> + iocg = cgroup_to_io_cgroup(cgroup);
> + spin_lock_irq(&iocg->lock);
> + /* Loop through all the io groups and print statistics */
> + hlist_for_each_entry_rcu(iog, n, &iocg->group_data, group_node) {
> + /*
> + * There might be groups which are not functional and
> + * waiting to be reclaimed upon cgoup deletion.
> + */
> + if (iog->key) {
> + seq_printf(m, "%u %u %lu\n", MAJOR(iog->dev),
> + MINOR(iog->dev), iog->dequeue);
> + }
> + }
> + spin_unlock_irq(&iocg->lock);
> + cgroup_unlock();
> +
> + return 0;
> +}
> +#endif
> +
> /**
> * bfq_group_chain_alloc - allocate a chain of groups.
> * @bfqd: queue descriptor.
> @@ -1263,7 +1460,9 @@ struct io_group *io_group_chain_alloc(struct request_queue *q, void *key,
> }
>
> blk_init_request_list(&iog->rl);
> -
> +#ifdef CONFIG_DEBUG_GROUP_IOSCHED
> + io_group_path(iog, iog->path, sizeof(iog->path));
> +#endif
> if (leaf == NULL) {
> leaf = iog;
> prev = leaf;
> @@ -1766,6 +1965,16 @@ struct cftype bfqio_files[] = {
> .name = "disk_sectors",
> .read_seq_string = io_cgroup_disk_sectors_read,
> },
> +#ifdef CONFIG_DEBUG_GROUP_IOSCHED
> + {
> + .name = "disk_queue",
> + .read_seq_string = io_cgroup_disk_queue_read,
> + },
> + {
> + .name = "disk_dequeue",
> + .read_seq_string = io_cgroup_disk_dequeue_read,
> + },
> +#endif
> };
>
> int iocg_populate(struct cgroup_subsys *subsys, struct cgroup *cgroup)
> @@ -2090,6 +2299,7 @@ struct cgroup_subsys io_subsys = {
> .destroy = iocg_destroy,
> .populate = iocg_populate,
> .subsys_id = io_subsys_id,
> + .use_id = 1,
> };
>
> /*
> @@ -2380,6 +2590,22 @@ EXPORT_SYMBOL(elv_get_slice_idle);
> void elv_ioq_served(struct io_queue *ioq, bfq_service_t served)
> {
> entity_served(&ioq->entity, served, ioq->nr_sectors);
> +
> +#ifdef CONFIG_DEBUG_GROUP_IOSCHED
> + {
> + struct elv_fq_data *efqd = ioq->efqd;
> + struct io_group *iog = ioq_to_io_group(ioq);
> + elv_log_ioq(efqd, ioq, "ioq served: QSt=0x%lx QSs=0x%lx"
> + " QTt=0x%lx QTs=0x%lx GTt=0x%lx "
> + " GTs=0x%lx rq_queued=%d",
> + served, ioq->nr_sectors,
> + ioq->entity.total_service,
> + ioq->entity.total_sector_service,
> + iog->entity.total_service,
> + iog->entity.total_sector_service,
> + ioq->nr_queued);
> + }
> +#endif
> }
>
> /* Tells whether ioq is queued in root group or not */
> @@ -2847,10 +3073,30 @@ static void __elv_set_active_ioq(struct elv_fq_data *efqd, struct io_queue *ioq,
> if (ioq) {
> struct io_group *iog = ioq_to_io_group(ioq);
> elv_log_ioq(efqd, ioq, "set_active, busy=%d ioprio=%d"
> - " weight=%ld group_weight=%ld",
> + " weight=%ld rq_queued=%d group_weight=%ld",
> efqd->busy_queues,
> ioq->entity.ioprio, ioq->entity.weight,
> - iog_weight(iog));
> + ioq->nr_queued, iog_weight(iog));
> +
> +#ifdef CONFIG_DEBUG_GROUP_IOSCHED
> + {
> + int nr_active = 0;
> + struct io_group *parent = NULL;
> +
> + parent = iog_parent(iog);
> + if (parent)
> + nr_active = elv_iog_nr_active(parent);
> +
> + elv_log_ioq(efqd, ioq, "set_active, ioq"
> + " nrgrps=%d QTt=0x%lx QTs=0x%lx GTt=0x%lx "
> + " GTs=0x%lx rq_queued=%d", nr_active,
> + ioq->entity.total_service,
> + ioq->entity.total_sector_service,
> + iog->entity.total_service,
> + iog->entity.total_sector_service,
> + ioq->nr_queued);
> + }
> +#endif
> ioq->slice_end = 0;
>
> elv_clear_ioq_wait_request(ioq);
> @@ -2927,12 +3173,26 @@ void elv_add_ioq_busy(struct elv_fq_data *efqd, struct io_queue *ioq)
> {
> BUG_ON(elv_ioq_busy(ioq));
> BUG_ON(ioq == efqd->active_queue);
> - elv_log_ioq(efqd, ioq, "add to busy");
> elv_activate_ioq(ioq, 0);
> elv_mark_ioq_busy(ioq);
> efqd->busy_queues++;
> if (elv_ioq_class_rt(ioq))
> efqd->busy_rt_queues++;
> +
> +#ifdef CONFIG_DEBUG_GROUP_IOSCHED
> + {
> + struct io_group *iog = ioq_to_io_group(ioq);
> + elv_log_ioq(efqd, ioq, "add to busy: QTt=0x%lx QTs=0x%lx"
> + " ioq grp=%s GTt=0x%lx GTs=0x%lx rq_queued=%d",
> + ioq->entity.total_service,
> + ioq->entity.total_sector_service,
> + iog->entity.total_service,
> + iog->entity.total_sector_service,
> + ioq->nr_queued);
> + }
> +#else
> + elv_log_ioq(efqd, ioq, "add to busy");
> +#endif
> }
>
> void elv_del_ioq_busy(struct elevator_queue *e, struct io_queue *ioq,
> @@ -2942,7 +3202,21 @@ void elv_del_ioq_busy(struct elevator_queue *e, struct io_queue *ioq,
>
> BUG_ON(!elv_ioq_busy(ioq));
> BUG_ON(ioq->nr_queued);
> +#ifdef CONFIG_DEBUG_GROUP_IOSCHED
> + {
> + struct io_group *iog = ioq_to_io_group(ioq);
> + elv_log_ioq(efqd, ioq, "del from busy: QTt=0x%lx "
> + "QTs=0x%lx ioq GTt=0x%lx GTs=0x%lx "
> + "rq_queued=%d",
> + ioq->entity.total_service,
> + ioq->entity.total_sector_service,
> + iog->entity.total_service,
> + iog->entity.total_sector_service,
> + ioq->nr_queued);
> + }
> +#else
> elv_log_ioq(efqd, ioq, "del from busy");
> +#endif
> elv_clear_ioq_busy(ioq);
> BUG_ON(efqd->busy_queues == 0);
> efqd->busy_queues--;
> @@ -3179,6 +3453,7 @@ void elv_ioq_request_add(struct request_queue *q, struct request *rq)
>
> elv_ioq_update_io_thinktime(ioq);
> elv_ioq_update_idle_window(q->elevator, ioq, rq);
> + elv_log_ioq(efqd, ioq, "add rq: rq_queued=%d", ioq->nr_queued);
>
> if (ioq == elv_active_ioq(q->elevator)) {
> /*
> @@ -3412,7 +3687,7 @@ void *elv_fq_select_ioq(struct request_queue *q, int force)
> }
>
> /* We are waiting for this queue to become busy before it expires.*/
> - if (efqd->fairness && elv_ioq_wait_busy(ioq)) {
> + if (elv_ioq_wait_busy(ioq)) {
> ioq = NULL;
> goto keep_queue;
> }
> diff --git a/block/elevator-fq.h b/block/elevator-fq.h
> index ff409ec..b5cff90 100644
> --- a/block/elevator-fq.h
> +++ b/block/elevator-fq.h
> @@ -251,6 +251,23 @@ struct io_group {
>
> /* request list associated with the group */
> struct request_list rl;
> +
> +#ifdef CONFIG_DEBUG_GROUP_IOSCHED
> + /* How many times this group has been added to active tree */
> + unsigned long queue;
> +
> + /* How long this group remained on active tree, in ms */
> + unsigned long queue_duration;
> +
> + /* When was this group added to active tree */
> + unsigned long queue_start;
> +
> + /* How many times this group has been removed from active tree */
> + unsigned long dequeue;
> +
> + /* Store cgroup path */
> + char path[128];
> +#endif
> };
>
> struct io_policy_node {
> @@ -353,9 +370,18 @@ extern int elv_slice_idle;
> extern int elv_slice_async;
>
> /* Logging facilities. */
> +#ifdef CONFIG_DEBUG_GROUP_IOSCHED
> +#define elv_log_ioq(efqd, ioq, fmt, args...) \
> +{ \
> + blk_add_trace_msg((efqd)->queue, "elv%d%c %s " fmt, (ioq)->pid, \
> + elv_ioq_sync(ioq) ? 'S' : 'A', \
> + ioq_to_io_group(ioq)->path, ##args); \
> +}
> +#else
> #define elv_log_ioq(efqd, ioq, fmt, args...) \
> blk_add_trace_msg((efqd)->queue, "elv%d%c " fmt, (ioq)->pid, \
> elv_ioq_sync(ioq) ? 'S' : 'A', ##args)
> +#endif
>
> #define elv_log(efqd, fmt, args...) \
> blk_add_trace_msg((efqd)->queue, "elv " fmt, ##args)

--
Regards
Gui Jianfeng