blkio: Group time used accounting and workload context save restore
o This patch introduces the functionality to do the accounting of group time
when a queue expires. This time used decides which is the group to go
next.
o Also introduce the functionlity to save and restore the workload type
context with-in group. It might happen that once we expire the cfq queue
and group, a different group will schedule in and we will lose the context
of the workload type. Hence save and restore it upon queue expiry.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 84887e2..55d2a21 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -115,6 +115,10 @@
/* fifo list of requests in sort_list */
struct list_head fifo;
+ /* time when queue got scheduled in to dispatch first request. */
+ unsigned long dispatch_start;
+ /* time when first request from queue completed and slice started. */
+ unsigned long slice_start;
unsigned long slice_end;
long slice_resid;
unsigned int slice_dispatch;
@@ -181,6 +185,10 @@
*/
struct cfq_rb_root service_trees[2][3];
struct cfq_rb_root service_tree_idle;
+
+ unsigned long saved_workload_slice;
+ enum wl_type_t saved_workload;
+ enum wl_prio_t saved_serving_prio;
};
/*
@@ -543,6 +551,7 @@
low_slice);
}
}
+ cfqq->slice_start = jiffies;
cfqq->slice_end = jiffies + slice;
cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
}
@@ -818,6 +827,58 @@
st->total_weight -= cfqg->weight;
if (!RB_EMPTY_NODE(&cfqg->rb_node))
cfq_rb_erase(&cfqg->rb_node, st);
+ cfqg->saved_workload_slice = 0;
+}
+
+static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq)
+{
+ unsigned int slice_used, allocated_slice;
+
+ /*
+ * Queue got expired before even a single request completed or
+ * got expired immediately after first request completion.
+ */
+ if (!cfqq->slice_start || cfqq->slice_start == jiffies) {
+ /*
+ * Also charge the seek time incurred to the group, otherwise
+ * if there are mutiple queues in the group, each can dispatch
+ * a single request on seeky media and cause lots of seek time
+ * and group will never know it.
+ */
+ slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start),
+ 1);
+ } else {
+ slice_used = jiffies - cfqq->slice_start;
+ allocated_slice = cfqq->slice_end - cfqq->slice_start;
+ if (slice_used > allocated_slice)
+ slice_used = allocated_slice;
+ }
+
+ cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u", slice_used);
+ return slice_used;
+}
+
+static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
+ struct cfq_queue *cfqq)
+{
+ struct cfq_rb_root *st = &cfqd->grp_service_tree;
+ unsigned int used_sl;
+
+ used_sl = cfq_cfqq_slice_usage(cfqq);
+
+ /* Can't update vdisktime while group is on service tree */
+ cfq_rb_erase(&cfqg->rb_node, st);
+ cfqg->vdisktime += cfq_scale_slice(used_sl, cfqg);
+ __cfq_group_service_tree_add(st, cfqg);
+
+ /* This group is being expired. Save the context */
+ if (time_after(cfqd->workload_expires, jiffies)) {
+ cfqg->saved_workload_slice = cfqd->workload_expires
+ - jiffies;
+ cfqg->saved_workload = cfqd->serving_type;
+ cfqg->saved_serving_prio = cfqd->serving_prio;
+ } else
+ cfqg->saved_workload_slice = 0;
}
/*
@@ -833,6 +894,7 @@
unsigned long rb_key;
struct cfq_rb_root *service_tree;
int left;
+ int new_cfqq = 1;
service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq),
cfqq_type(cfqq), cfqd);
@@ -861,6 +923,7 @@
}
if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
+ new_cfqq = 0;
/*
* same position, nothing more to do
*/
@@ -902,6 +965,8 @@
rb_link_node(&cfqq->rb_node, parent, p);
rb_insert_color(&cfqq->rb_node, &service_tree->rb);
service_tree->count++;
+ if (add_front || !new_cfqq)
+ return;
cfq_group_service_tree_add(cfqd, cfqq->cfqg);
}
@@ -1218,6 +1283,8 @@
{
if (cfqq) {
cfq_log_cfqq(cfqd, cfqq, "set_active");
+ cfqq->slice_start = 0;
+ cfqq->dispatch_start = jiffies;
cfqq->slice_end = 0;
cfqq->slice_dispatch = 0;
@@ -1255,6 +1322,8 @@
cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
}
+ cfq_group_served(cfqd, cfqq->cfqg, cfqq);
+
if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
cfq_del_cfqq_rr(cfqd, cfqq);
@@ -1263,6 +1332,9 @@
if (cfqq == cfqd->active_queue)
cfqd->active_queue = NULL;
+ if (&cfqq->cfqg->rb_node == cfqd->grp_service_tree.active)
+ cfqd->grp_service_tree.active = NULL;
+
if (cfqd->active_cic) {
put_io_context(cfqd->active_cic->ioc);
cfqd->active_cic = NULL;
@@ -1747,6 +1819,13 @@
struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd);
cfqd->serving_group = cfqg;
+
+ /* Restore the workload type data */
+ if (cfqg->saved_workload_slice) {
+ cfqd->workload_expires = jiffies + cfqg->saved_workload_slice;
+ cfqd->serving_type = cfqg->saved_workload;
+ cfqd->serving_prio = cfqg->saved_serving_prio;
+ }
choose_service_tree(cfqd, cfqg);
}
