blkio: Introduce per cfq group weights and vdisktime calculations

o Bring in the per cfq group weight and how vdisktime is calculated for the
  group. Also bring in the functionality of updating the min_vdisktime of
  the group service tree.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
index be0280d..fa95fa7 100644 (file)
--- a/block/Kconfig.iosched
+++ b/block/Kconfig.iosched
@@ -23,7 +23,6 @@ config IOSCHED_DEADLINE
 
 config IOSCHED_CFQ
        tristate "CFQ I/O scheduler"
-       select BLK_CGROUP
        default y
        ---help---
          The CFQ I/O scheduler tries to distribute bandwidth equally
@@ -33,6 +32,14 @@ config IOSCHED_CFQ
 
          This is the default I/O scheduler.
 
+config CFQ_GROUP_IOSCHED
+       bool "CFQ Group Scheduling support"
+       depends on IOSCHED_CFQ && CGROUPS
+       select BLK_CGROUP
+       default n
+       ---help---
+         Enable group IO scheduling in CFQ.
+
 choice
        prompt "Default I/O scheduler"
        default DEFAULT_CFQ

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index e1f822a..019f28e 100644 (file)
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -13,6 +13,7 @@
 #include <linux/rbtree.h>
 #include <linux/ioprio.h>
 #include <linux/blktrace_api.h>
+#include "blk-cgroup.h"
 
 /*
  * tunables
@@ -49,6 +50,7 @@ static const int cfq_hist_divisor = 4;
 
 #define CFQ_SLICE_SCALE                (5)
 #define CFQ_HW_QUEUE_MIN       (5)
+#define CFQ_SERVICE_SHIFT       12
 
 #define RQ_CIC(rq)             \
        ((struct cfq_io_context *) (rq)->elevator_private)
@@ -79,6 +81,7 @@ struct cfq_rb_root {
        struct rb_node *left;
        unsigned count;
        u64 min_vdisktime;
+       struct rb_node *active;
 };
 #define CFQ_RB_ROOT    (struct cfq_rb_root) { RB_ROOT, NULL, 0, 0, }
 
@@ -163,6 +166,7 @@ struct cfq_group {
 
        /* group service_tree key */
        u64 vdisktime;
+       unsigned int weight;
        bool on_st;
 
        /* number of cfqq currently on this group */
@@ -434,6 +438,51 @@ cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
        return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
 }
 
+static inline u64 cfq_scale_slice(unsigned long delta, struct cfq_group *cfqg)
+{
+       u64 d = delta << CFQ_SERVICE_SHIFT;
+
+       d = d * BLKIO_WEIGHT_DEFAULT;
+       do_div(d, cfqg->weight);
+       return d;
+}
+
+static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime)
+{
+       s64 delta = (s64)(vdisktime - min_vdisktime);
+       if (delta > 0)
+               min_vdisktime = vdisktime;
+
+       return min_vdisktime;
+}
+
+static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime)
+{
+       s64 delta = (s64)(vdisktime - min_vdisktime);
+       if (delta < 0)
+               min_vdisktime = vdisktime;
+
+       return min_vdisktime;
+}
+
+static void update_min_vdisktime(struct cfq_rb_root *st)
+{
+       u64 vdisktime = st->min_vdisktime;
+       struct cfq_group *cfqg;
+
+       if (st->active) {
+               cfqg = rb_entry_cfqg(st->active);
+               vdisktime = cfqg->vdisktime;
+       }
+
+       if (st->left) {
+               cfqg = rb_entry_cfqg(st->left);
+               vdisktime = min_vdisktime(vdisktime, cfqg->vdisktime);
+       }
+
+       st->min_vdisktime = max_vdisktime(st->min_vdisktime, vdisktime);
+}
+
 /*
  * get averaged number of queues of RT/BE priority.
  * average is updated, with a formula that gives more weight to higher numbers,
@@ -734,8 +783,12 @@ cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
 {
        struct cfq_rb_root *st = &cfqd->grp_service_tree;
 
+       if (st->active == &cfqg->rb_node)
+               st->active = NULL;
+
        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;
@@ -1654,10 +1707,14 @@ static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
 {
        struct cfq_rb_root *st = &cfqd->grp_service_tree;
+       struct cfq_group *cfqg;
 
        if (RB_EMPTY_ROOT(&st->rb))
                return NULL;
-       return cfq_rb_first_group(st);
+       cfqg = cfq_rb_first_group(st);
+       st->active = &cfqg->rb_node;
+       update_min_vdisktime(st);
+       return cfqg;
 }
 
 static void cfq_choose_cfqg(struct cfq_data *cfqd)
@@ -3150,6 +3207,9 @@ static void *cfq_init_queue(struct request_queue *q)
                *st = CFQ_RB_ROOT;
        RB_CLEAR_NODE(&cfqg->rb_node);
 
+       /* Give preference to root group over other groups */
+       cfqg->weight = 2*BLKIO_WEIGHT_DEFAULT;
+
        /*
         * Not strictly needed (since RB_ROOT just clears the node and we
         * zeroed cfqd on alloc), but better be safe in case someone decides