Messages in this thread Patch in this message | | | From | Justin TerAvest <> | Date | Mon, 14 Feb 2011 15:32:49 -0800 | Subject | Re: [PATCH 3/6 v4] cfq-iosched: Introduce vdisktime and io weight for CFQ queue |
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On Wed, Feb 9, 2011 at 11:47 PM, Gui Jianfeng <guijianfeng@cn.fujitsu.com> wrote: > Introduce vdisktime and io weight for CFQ queue scheduling. Currently, io priority > maps to a range [100,1000]. It also gets rid of cfq_slice_offset() logic and makes > use the same scheduling algorithm as CFQ group does. This helps for CFQ queue and > group scheduling on the same service tree.
Hi Gui, I have a couple of questions inline.
Thanks, Justin
> > Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com> > --- > block/cfq-iosched.c | 219 +++++++++++++++++++++++++++++++++++++++------------ > 1 files changed, 167 insertions(+), 52 deletions(-) > > diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c > index f3a126e..41cef2e 100644 > --- a/block/cfq-iosched.c > +++ b/block/cfq-iosched.c > @@ -39,6 +39,13 @@ static const int cfq_hist_divisor = 4; > */ > #define CFQ_IDLE_DELAY (HZ / 5) > > +/* > + * The base boosting value. > + */ > +#define CFQ_BOOST_SYNC_BASE (HZ / 10) > +#define CFQ_BOOST_ASYNC_BASE (HZ / 25) > + > + > /* > * below this threshold, we consider thinktime immediate > */ > @@ -99,10 +106,7 @@ struct cfq_entity { > struct cfq_rb_root *service_tree; > /* service_tree member */ > struct rb_node rb_node; > - /* service_tree key, represent the position on the tree */ > - unsigned long rb_key; > - > - /* group service_tree key */ > + /* service_tree key */ > u64 vdisktime; > bool is_group_entity; > unsigned int weight; > @@ -114,6 +118,8 @@ struct cfq_entity { > struct cfq_queue { > /* The schedule entity */ > struct cfq_entity cfqe; > + /* Reposition time */ > + unsigned long reposition_time;
Can this be addition time or something else instead? This is set, even when we are not repositioning among service trees.
> /* reference count */ > int ref; > /* various state flags, see below */ > @@ -312,6 +318,24 @@ struct cfq_data { > struct rcu_head rcu; > }; > > +/* > + * Map io priority(7 ~ 0) to io weight(100 ~ 1000) as follows > + * prio 0 1 2 3 4 5 6 7 > + * weight 1000 868 740 612 484 356 228 100 > + */ > +static inline unsigned int cfq_prio_to_weight(unsigned short ioprio) > +{ > + unsigned int step; > + > + BUG_ON(ioprio >= IOPRIO_BE_NR); > + > + step = (BLKIO_WEIGHT_MAX - BLKIO_WEIGHT_MIN) / (IOPRIO_BE_NR - 1); > + if (ioprio == 0) > + return BLKIO_WEIGHT_MAX; > + > + return BLKIO_WEIGHT_MIN + (IOPRIO_BE_NR - ioprio - 1) * step; > +} > + > static inline struct cfq_queue * > cfqq_of_entity(struct cfq_entity *cfqe) > { > @@ -840,16 +864,6 @@ cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq, > return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last)); > } > > -static unsigned long cfq_slice_offset(struct cfq_data *cfqd, > - struct cfq_queue *cfqq) > -{ > - /* > - * just an approximation, should be ok. > - */ > - return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) - > - cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio)); > -} > - > static inline s64 > entity_key(struct cfq_rb_root *st, struct cfq_entity *entity) > { > @@ -1199,6 +1213,21 @@ static inline void cfq_put_cfqg(struct cfq_group *cfqg) {} > > #endif /* GROUP_IOSCHED */ > > +static inline u64 cfq_get_boost(struct cfq_data *cfqd, > + struct cfq_queue *cfqq) > +{ > + u64 d; > + > + if (cfq_cfqq_sync(cfqq)) > + d = CFQ_BOOST_SYNC_BASE << CFQ_SERVICE_SHIFT; > + else > + d = CFQ_BOOST_ASYNC_BASE << CFQ_SERVICE_SHIFT; > + > + d = d * BLKIO_WEIGHT_DEFAULT; > + do_div(d, cfqq->cfqe.weight); > + return d; > +}
The logic for cfq_get_boost() looks a lot like cfq_scale_slice(). Instead of duplicating code, can't it just be u64 d; if (cfq_cfqq_sync(cfqq)) return cfq_scale_slice(CFQ_BOOST_SYNC_BASE, cfqq->cfqe); else return cfq_scale_slice(CFQ_BOOST_ASYNC_BASE, cfqq->cfqe);
> + > /* > * The cfqd->service_trees holds all pending cfq_queue's that have > * requests waiting to be processed. It is sorted in the order that > @@ -1210,13 +1239,14 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq, > struct cfq_entity *cfqe; > struct rb_node **p, *parent; > struct cfq_entity *__cfqe; > - unsigned long rb_key; > - struct cfq_rb_root *service_tree; > + struct cfq_rb_root *service_tree, *orig_st; > int left; > int new_cfqq = 1; > int group_changed = 0; > + s64 key; > > cfqe = &cfqq->cfqe; > + orig_st = cfqe->service_tree; > > #ifdef CONFIG_CFQ_GROUP_IOSCHED > if (!cfqd->cfq_group_isolation > @@ -1224,8 +1254,15 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq, > && cfqq->cfqg && cfqq->cfqg != &cfqd->root_group) { > /* Move this cfq to root group */ > cfq_log_cfqq(cfqd, cfqq, "moving to root group"); > - if (!RB_EMPTY_NODE(&cfqe->rb_node)) > + if (!RB_EMPTY_NODE(&cfqe->rb_node)) { > cfq_group_service_tree_del(cfqd, cfqq->cfqg); > + /* > + * Group changed, dequeue this CFQ queue from the > + * original service tree. > + */ > + cfq_rb_erase(&cfqe->rb_node, cfqe->service_tree); > + orig_st->total_weight -= cfqe->weight; > + } > cfqq->orig_cfqg = cfqq->cfqg; > cfqq->cfqg = &cfqd->root_group; > cfqd->root_group.ref++; > @@ -1234,8 +1271,15 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq, > && cfqq_type(cfqq) == SYNC_WORKLOAD && cfqq->orig_cfqg) { > /* cfqq is sequential now needs to go to its original group */ > BUG_ON(cfqq->cfqg != &cfqd->root_group); > - if (!RB_EMPTY_NODE(&cfqe->rb_node)) > + if (!RB_EMPTY_NODE(&cfqe->rb_node)) { > cfq_group_service_tree_del(cfqd, cfqq->cfqg); > + /* > + * Group changed, dequeue this CFQ queue from the > + * original service tree. > + */ > + cfq_rb_erase(&cfqe->rb_node, cfqe->service_tree); > + orig_st->total_weight -= cfqe->weight; > + } > cfq_put_cfqg(cfqq->cfqg); > cfqq->cfqg = cfqq->orig_cfqg; > cfqq->orig_cfqg = NULL; > @@ -1246,47 +1290,68 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq, > > service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq), > cfqq_type(cfqq)); > + if (RB_EMPTY_NODE(&cfqe->rb_node)) { > + /* > + * If this CFQ queue moves to another group, the original > + * vdisktime makes no sense any more, reset the vdisktime > + * here. > + */ > + parent = rb_last(&service_tree->rb); > + if (parent) { > + u64 pos_offset; > + > + /* > + * Estimate the position according to its weight and > + * ioprio. > + */ > + pos_offset = cfq_get_boost(cfqd, cfqq); > + /* Debug purpose, should remove. */ > + cfq_log_cfqq(cfqd, cfqq, "pos_offset: %llu", > + pos_offset); > + cfqe->vdisktime = service_tree->min_vdisktime + > + pos_offset; > + } else > + cfqe->vdisktime = service_tree->min_vdisktime; > + > + goto insert; > + } > + > + /* > + * Ok, we get here, this CFQ queue is on the service tree, dequeue it > + * firstly. > + */ > + cfq_rb_erase(&cfqe->rb_node, cfqe->service_tree); > + orig_st->total_weight -= cfqe->weight; > + > + new_cfqq = 0; > + > if (cfq_class_idle(cfqq)) { > - rb_key = CFQ_IDLE_DELAY; > parent = rb_last(&service_tree->rb); > if (parent && parent != &cfqe->rb_node) { > __cfqe = rb_entry(parent, struct cfq_entity, rb_node); > - rb_key += __cfqe->rb_key; > + cfqe->vdisktime = __cfqe->vdisktime + CFQ_IDLE_DELAY; > } else > - rb_key += jiffies; > + cfqe->vdisktime = service_tree->min_vdisktime; > } else if (!add_front) { > /* > - * Get our rb key offset. Subtract any residual slice > - * value carried from last service. A negative resid > - * count indicates slice overrun, and this should position > - * the next service time further away in the tree. > + * We charge the CFQ queue by the time this queue runs, and > + * repsition it on the service tree. > */ > - rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies; > - rb_key -= cfqq->slice_resid; > + unsigned int used_sl; > + > + used_sl = cfq_cfqq_slice_usage(cfqq); > + cfqe->vdisktime += cfq_scale_slice(used_sl, cfqe); > cfqq->slice_resid = 0; > } else { > - rb_key = -HZ; > - __cfqe = cfq_rb_first(service_tree); > - rb_key += __cfqe ? __cfqe->rb_key : jiffies; > - } > - > - if (!RB_EMPTY_NODE(&cfqe->rb_node)) { > - new_cfqq = 0; > - /* > - * same position, nothing more to do > - */ > - if (rb_key == cfqe->rb_key && > - cfqe->service_tree == service_tree) > - return; > - > - cfq_rb_erase(&cfqe->rb_node, cfqe->service_tree); > - cfqe->service_tree = NULL; > + cfqe->vdisktime = service_tree->min_vdisktime; > } > > +insert: > left = 1; > parent = NULL; > cfqe->service_tree = service_tree; > p = &service_tree->rb.rb_node; > + key = entity_key(service_tree, cfqe); > while (*p) { > struct rb_node **n; > > @@ -1296,7 +1361,7 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq, > /* > * sort by key, that represents service time. > */ > - if (time_before(rb_key, __cfqe->rb_key)) > + if (key < entity_key(service_tree, __cfqe)) > n = &(*p)->rb_left; > else { > n = &(*p)->rb_right; > @@ -1309,10 +1374,12 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq, > if (left) > service_tree->left = &cfqe->rb_node; > > - cfqe->rb_key = rb_key; > rb_link_node(&cfqe->rb_node, parent, p); > rb_insert_color(&cfqe->rb_node, &service_tree->rb); > + update_min_vdisktime(service_tree); > service_tree->count++; > + service_tree->total_weight += cfqe->weight;
I'm confused by this line. Why are we doing some adjustment for cfqe weight that we weren't doing previously? I think cfq_group_service_tree_add below will still do the total_weight adjustment.
> + cfqq->reposition_time = jiffies; > if ((add_front || !new_cfqq) && !group_changed) > return; > cfq_group_service_tree_add(cfqd, cfqq->cfqg); > @@ -1414,14 +1481,18 @@ static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) > static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) > { > struct cfq_entity *cfqe; > + struct cfq_rb_root *service_tree; > + > cfq_log_cfqq(cfqd, cfqq, "del_from_rr"); > BUG_ON(!cfq_cfqq_on_rr(cfqq)); > cfq_clear_cfqq_on_rr(cfqq); > > cfqe = &cfqq->cfqe; > + service_tree = cfqe->service_tree; > > if (!RB_EMPTY_NODE(&cfqe->rb_node)) { > cfq_rb_erase(&cfqe->rb_node, cfqe->service_tree); > + service_tree->total_weight -= cfqe->weight; > cfqe->service_tree = NULL; > } > if (cfqq->p_root) { > @@ -2120,23 +2191,36 @@ static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq) > } > } > > +/* > + * The time when a CFQ queue is put onto a service tree is recoreded in > + * cfqq->reposition_time. Currently, we check the first priority CFQ queues > + * on each service tree, and select the workload type that contains the lowest > + * reposition_time CFQ queue among them. > + */ > static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd, > struct cfq_group *cfqg, enum wl_prio_t prio) > { > struct cfq_entity *cfqe; > + struct cfq_queue *cfqq; > + unsigned long lowest_start_time; > int i; > - bool key_valid = false; > - unsigned long lowest_key = 0; > + bool time_valid = false; > enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD; > > + /* > + * TODO: We may take io priority and io class into account when > + * choosing a workload type. But for the time being just make use of > + * reposition_time only. > + */ > for (i = 0; i <= SYNC_WORKLOAD; ++i) { > - /* select the one with lowest rb_key */ > cfqe = cfq_rb_first(service_tree_for(cfqg, prio, i)); > - if (cfqe && > - (!key_valid || time_before(cfqe->rb_key, lowest_key))) { > - lowest_key = cfqe->rb_key; > + cfqq = cfqq_of_entity(cfqe); > + if (cfqe && (!time_valid || > + time_before(cfqq->reposition_time, > + lowest_start_time))) { > + lowest_start_time = cfqq->reposition_time; > cur_best = i; > - key_valid = true; > + time_valid = true; > } > } > > @@ -2808,10 +2892,13 @@ static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc) > { > struct task_struct *tsk = current; > int ioprio_class; > + struct cfq_entity *cfqe; > > if (!cfq_cfqq_prio_changed(cfqq)) > return; > > + cfqe = &cfqq->cfqe; > + > ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio); > switch (ioprio_class) { > default: > @@ -2838,6 +2925,17 @@ static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc) > break; > } > > + if (!RB_EMPTY_NODE(&cfqe->rb_node)) { > + /* > + * If this CFQ entity is already on service tree, we need to > + * adjust service tree's total weight accordingly. > + */ > + cfqe->service_tree->total_weight -= cfqe->weight; > + cfqe->weight = cfq_prio_to_weight(cfqq->ioprio); > + cfqe->service_tree->total_weight += cfqe->weight; > + } else > + cfqe->weight = cfq_prio_to_weight(cfqq->ioprio); > + > /* > * keep track of original prio settings in case we have to temporarily > * elevate the priority of this queue > @@ -3572,6 +3670,9 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq) > */ > static void cfq_prio_boost(struct cfq_queue *cfqq) > { > + struct cfq_entity *cfqe; > + > + cfqe = &cfqq->cfqe; > if (has_fs_excl()) { > /* > * boost idle prio on transactions that would lock out other > @@ -3588,6 +3689,20 @@ static void cfq_prio_boost(struct cfq_queue *cfqq) > cfqq->ioprio_class = cfqq->org_ioprio_class; > cfqq->ioprio = cfqq->org_ioprio; > } > + > + /* > + * update the io weight if io priority gets changed. > + */ > + if (!RB_EMPTY_NODE(&cfqe->rb_node)) { > + /* > + * If this CFQ entity is already on service tree, we need to > + * adjust service tree's total weight accordingly. > + */ > + cfqe->service_tree->total_weight -= cfqe->weight; > + cfqe->weight = cfq_prio_to_weight(cfqq->ioprio); > + cfqe->service_tree->total_weight += cfqe->weight; > + } else > + cfqe->weight = cfq_prio_to_weight(cfqq->ioprio); > } > > static inline int __cfq_may_queue(struct cfq_queue *cfqq) > -- > 1.7.1 > > > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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