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Date: Tue, 1 Dec 2009 05:25:36 +0530
From: Divyesh Shah <dpshah@...gle.com>
To: Vivek Goyal <vgoyal@...hat.com>
Cc: linux-kernel@...r.kernel.org, jens.axboe@...cle.com,
nauman@...gle.com, lizf@...fujitsu.com, ryov@...inux.co.jp,
fernando@....ntt.co.jp, s-uchida@...jp.nec.com, taka@...inux.co.jp,
guijianfeng@...fujitsu.com, jmoyer@...hat.com,
righi.andrea@...il.com, m-ikeda@...jp.nec.com, czoccolo@...il.com,
Alan.Brunelle@...com
Subject: Re: [PATCH 05/21] blkio: Introduce the root service tree for cfq
groups
On Mon, Nov 30, 2009 at 8:29 AM, Vivek Goyal <vgoyal@...hat.com> wrote:
> o So far we just had one cfq_group in cfq_data. To create space for more than
> one cfq_group, we need to have a service tree of groups where all the groups
> can be queued if they have active cfq queues backlogged in these.
>
> Signed-off-by: Vivek Goyal <vgoyal@...hat.com>
> ---
> block/cfq-iosched.c | 136 +++++++++++++++++++++++++++++++++++++++++++++++++-
> 1 files changed, 133 insertions(+), 3 deletions(-)
>
> diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
> index a0d0a83..0a284be 100644
> --- a/block/cfq-iosched.c
> +++ b/block/cfq-iosched.c
> @@ -77,8 +77,9 @@ struct cfq_rb_root {
> struct rb_root rb;
> struct rb_node *left;
> unsigned count;
> + u64 min_vdisktime;
> };
> -#define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, 0, }
> +#define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, 0, 0, }
>
> /*
> * Per process-grouping structure
> @@ -156,6 +157,16 @@ enum wl_type_t {
>
> /* This is per cgroup per device grouping structure */
> struct cfq_group {
> + /* group service_tree member */
> + struct rb_node rb_node;
> +
> + /* group service_tree key */
> + u64 vdisktime;
> + bool on_st;
> +
> + /* number of cfqq currently on this group */
> + int nr_cfqq;
> +
> /*
> * rr lists of queues with requests, onle rr for each priority class.
> * Counts are embedded in the cfq_rb_root
> @@ -169,6 +180,8 @@ struct cfq_group {
> */
> struct cfq_data {
> struct request_queue *queue;
> + /* Root service tree for cfq_groups */
> + struct cfq_rb_root grp_service_tree;
> struct cfq_group root_group;
>
> /*
> @@ -251,6 +264,9 @@ static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg,
> enum wl_type_t type,
> struct cfq_data *cfqd)
> {
> + if (!cfqg)
> + return NULL;
> +
> if (prio == IDLE_WORKLOAD)
> return &cfqg->service_tree_idle;
>
> @@ -587,6 +603,17 @@ static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
> return NULL;
> }
>
> +static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root)
> +{
> + if (!root->left)
> + root->left = rb_first(&root->rb);
> +
> + if (root->left)
> + return rb_entry(root->left, struct cfq_group, rb_node);
Can you please define a cfqg_entry macro and reuse that at different
places in the code?
#define cfqg_entry(ptr) rb_entry(ptr, struct cfq_group, rb_node)
> +
> + return NULL;
> +}
> +
> static void rb_erase_init(struct rb_node *n, struct rb_root *root)
> {
> rb_erase(n, root);
> @@ -643,6 +670,83 @@ static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
> cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
> }
>
> +static inline s64
> +cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg)
> +{
> + return cfqg->vdisktime - st->min_vdisktime;
> +}
> +
> +static void
> +__cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
> +{
> + struct rb_node **node = &st->rb.rb_node;
> + struct rb_node *parent = NULL;
> + struct cfq_group *__cfqg;
> + s64 key = cfqg_key(st, cfqg);
> + int left = 1;
> +
> + while (*node != NULL) {
> + parent = *node;
> + __cfqg = rb_entry(parent, struct cfq_group, rb_node);
> +
> + if (key < cfqg_key(st, __cfqg))
> + node = &parent->rb_left;
> + else {
> + node = &parent->rb_right;
> + left = 0;
> + }
> + }
> +
> + if (left)
> + st->left = &cfqg->rb_node;
> +
> + rb_link_node(&cfqg->rb_node, parent, node);
> + rb_insert_color(&cfqg->rb_node, &st->rb);
> +}
> +
> +static void
> +cfq_group_service_tree_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
> +{
> + struct cfq_rb_root *st = &cfqd->grp_service_tree;
> + struct cfq_group *__cfqg;
> + struct rb_node *n;
> +
> + cfqg->nr_cfqq++;
> + if (cfqg->on_st)
> + return;
> +
> + /*
> + * Currently put the group at the end. Later implement something
> + * so that groups get lesser vtime based on their weights, so that
> + * if group does not loose all if it was not continously backlogged.
> + */
> + n = rb_last(&st->rb);
> + if (n) {
> + __cfqg = rb_entry(n, struct cfq_group, rb_node);
> + cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
> + } else
> + cfqg->vdisktime = st->min_vdisktime;
> +
> + __cfq_group_service_tree_add(st, cfqg);
> + cfqg->on_st = true;
> +}
> +
> +static void
> +cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
> +{
> + struct cfq_rb_root *st = &cfqd->grp_service_tree;
> +
> + BUG_ON(cfqg->nr_cfqq < 1);
> + cfqg->nr_cfqq--;
> + /* If there are other cfq queues under this group, don't delete it */
> + if (cfqg->nr_cfqq)
> + return;
> +
> + cfqg->on_st = false;
> + if (!RB_EMPTY_NODE(&cfqg->rb_node))
> + cfq_rb_erase(&cfqg->rb_node, st);
> +}
> +
> /*
> * The cfqd->service_trees holds all pending cfq_queue's that have
> * requests waiting to be processed. It is sorted in the order that
> @@ -725,6 +829,7 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
> rb_link_node(&cfqq->rb_node, parent, p);
> rb_insert_color(&cfqq->rb_node, &service_tree->rb);
> service_tree->count++;
> + cfq_group_service_tree_add(cfqd, cfqq->cfqg);
> }
>
> static struct cfq_queue *
> @@ -835,6 +940,7 @@ static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
> cfqq->p_root = NULL;
> }
>
> + cfq_group_service_tree_del(cfqd, cfqq->cfqg);
> BUG_ON(!cfqd->busy_queues);
> cfqd->busy_queues--;
> }
> @@ -1111,6 +1217,9 @@ static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
> if (!cfqd->rq_queued)
> return NULL;
>
> + /* There is nothing to dispatch */
> + if (!service_tree)
> + return NULL;
> if (RB_EMPTY_ROOT(&service_tree->rb))
> return NULL;
> return cfq_rb_first(service_tree);
> @@ -1480,6 +1589,12 @@ static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
> unsigned count;
> struct cfq_rb_root *st;
>
> + if (!cfqg) {
> + cfqd->serving_prio = IDLE_WORKLOAD;
> + cfqd->workload_expires = jiffies + 1;
> + return;
> + }
> +
> /* Choose next priority. RT > BE > IDLE */
> if (cfq_busy_queues_wl(RT_WORKLOAD, cfqd))
> cfqd->serving_prio = RT_WORKLOAD;
> @@ -1538,10 +1653,21 @@ static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
> cfqd->noidle_tree_requires_idle = false;
> }
>
> +static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
> +{
> + struct cfq_rb_root *st = &cfqd->grp_service_tree;
> +
> + if (RB_EMPTY_ROOT(&st->rb))
> + return NULL;
> + return cfq_rb_first_group(st);
> +}
> +
> static void cfq_choose_cfqg(struct cfq_data *cfqd)
> {
> - cfqd->serving_group = &cfqd->root_group;
> - choose_service_tree(cfqd, &cfqd->root_group);
> + struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd);
> +
> + cfqd->serving_group = cfqg;
> + choose_service_tree(cfqd, cfqg);
> }
>
> /*
> @@ -3017,10 +3143,14 @@ static void *cfq_init_queue(struct request_queue *q)
> if (!cfqd)
> return NULL;
>
> + /* Init root service tree */
> + cfqd->grp_service_tree = CFQ_RB_ROOT;
> +
> /* Init root group */
> cfqg = &cfqd->root_group;
> for_each_cfqg_st(cfqg, i, j, st)
> *st = CFQ_RB_ROOT;
> + RB_CLEAR_NODE(&cfqg->rb_node);
>
> /*
> * Not strictly needed (since RB_ROOT just clears the node and we
> --
> 1.6.2.5
>
>
--
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