Re: [PATCH 11/20] blkio: Some CFQ debugging Aid

[Divyesh Shah <dpshah@google.com>]

In the previous patchset when merged with the bio tracking patches we
had a very convenient
 biocg_id we could use for debugging. If the eventual plan is to merge
the biotrack patches, do you think it makes sense to introduce the
per-blkio cgroup id here when DEBUG_BLK_CGROUP=y and use that for all
traces? The cgroup path name seems ugly to me.

-Divyesh

On Tue, Nov 3, 2009 at 3:43 PM, Vivek Goyal <vgoyal@redhat.com> wrote:
> o Some CFQ debugging Aid.
>
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
> ---
>  block/Kconfig         |    9 +++++++++
>  block/Kconfig.iosched |    9 +++++++++
>  block/blk-cgroup.c    |    4 ++++
>  block/blk-cgroup.h    |   13 +++++++++++++
>  block/cfq-iosched.c   |   33 +++++++++++++++++++++++++++++++++
>  5 files changed, 68 insertions(+), 0 deletions(-)
>
> diff --git a/block/Kconfig b/block/Kconfig
> index 6ba1a8e..e20fbde 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 a521c69..9c5f0b5 100644
> --- a/block/Kconfig.iosched
> +++ b/block/Kconfig.iosched
> @@ -48,6 +48,15 @@ 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 a62b8a3..4c68682 100644
> --- a/block/blk-cgroup.c
> +++ b/block/blk-cgroup.c
> @@ -39,6 +39,10 @@ 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 2bf736b..cb72c35 100644
> --- a/block/blk-cgroup.h
> +++ b/block/blk-cgroup.h
> @@ -26,12 +26,25 @@ 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
> +
>  extern struct blkio_cgroup blkio_root_cgroup;
>  struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup);
>  void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
> diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
> index b9a052b..2fde3c4 100644
> --- a/block/cfq-iosched.c
> +++ b/block/cfq-iosched.c
> @@ -258,8 +258,29 @@ CFQ_CFQQ_FNS(sync);
>  CFQ_CFQQ_FNS(coop);
>  #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_to_cfqg((cfqq))->blkg), ##args);
> +
> +#define cfq_log_cfqe(cfqd, cfqe, fmt, args...)                 \
> +       if (cfqq_of(cfqe)) {                                            \
> +               struct cfq_queue *cfqq = cfqq_of(cfqe);                 \
> +               blk_add_trace_msg((cfqd)->queue, "cfq%d%c %s " fmt,     \
> +                       (cfqq)->pid, cfq_cfqq_sync((cfqq)) ? 'S' : 'A', \
> +                       blkg_path(&cfqq_to_cfqg((cfqq))->blkg), ##args);\
> +       } else {                                                        \
> +               struct cfq_group *cfqg = cfqg_of(cfqe);                 \
> +               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_cfqe(cfqd, cfqe, fmt, args...)
> +#endif
> +
>  #define cfq_log(cfqd, fmt, args...)    \
>        blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
>
> @@ -400,6 +421,8 @@ cfq_init_cfqe_parent(struct cfq_entity *cfqe, struct cfq_entity *p_cfqe)
>  #define for_each_entity(entity)        \
>        for (; entity && entity->parent; entity = entity->parent)
>
> +#define cfqe_is_cfqq(cfqe)     (!(cfqe)->my_sd)
> +
>  static inline struct cfq_group *cfqg_of_blkg(struct blkio_group *blkg)
>  {
>        if (blkg)
> @@ -588,6 +611,8 @@ void cfq_delink_blkio_group(void *key, struct blkio_group *blkg)
>  #define for_each_entity(entity)        \
>        for (; entity != NULL; entity = NULL)
>
> +#define cfqe_is_cfqq(cfqe)     1
> +
>  static void cfq_release_cfq_groups(struct cfq_data *cfqd) {}
>  static inline void cfq_get_cfqg_ref(struct cfq_group *cfqg) {}
>  static inline void cfq_put_cfqg(struct cfq_group *cfqg) {}
> @@ -885,6 +910,10 @@ static void dequeue_cfqq(struct cfq_queue *cfqq)
>                struct cfq_sched_data *sd = cfq_entity_sched_data(cfqe);
>
>                dequeue_cfqe(cfqe);
> +               if (!cfqe_is_cfqq(cfqe)) {
> +                       cfq_log_cfqe(cfqq->cfqd, cfqe, "del_from_rr group");
> +               }
> +
>                /* Do not dequeue parent if it has other entities under it */
>                if (sd->nr_active)
>                        break;
> @@ -970,6 +999,8 @@ static void requeue_cfqq(struct cfq_queue *cfqq, int add_front)
>
>  static void cfqe_served(struct cfq_entity *cfqe, unsigned long served)
>  {
> +       struct cfq_data *cfqd = cfqq_of(cfqe)->cfqd;
> +
>        for_each_entity(cfqe) {
>                /*
>                 * Can't update entity disk time while it is on sorted rb-tree
> @@ -979,6 +1010,8 @@ static void cfqe_served(struct cfq_entity *cfqe, unsigned long served)
>                cfqe->vdisktime += cfq_delta_fair(served, cfqe);
>                update_min_vdisktime(cfqe->st);
>                __enqueue_cfqe(cfqe->st, cfqe, 0);
> +               cfq_log_cfqe(cfqd, cfqe, "served: vt=%llx min_vt=%llx",
> +                               cfqe->vdisktime, cfqe->st->min_vdisktime);
>
>                /* If entity prio class has changed, take that into account */
>                if (unlikely(cfqe->ioprio_class_changed)) {
> --
> 1.6.2.5
>
>