cfq-iosched: Always provide group isolation.

Effectively, make group_isolation=1 the default and remove the tunable.
The setting group_isolation=0 was because by default we idle on
sync-noidle tree and on fast devices, this can be very harmful for
throughput.

However, this problem can also be addressed by tuning slice_idle and
possibly group_idle on faster storage devices.

This change simplifies the CFQ code by removing the feature entirely.

Signed-off-by: Justin TerAvest <teravest@google.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 1 insertions, 36 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index f27ff3efe6cd..3202c7e87fb3 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -146,7 +146,6 @@ struct cfq_queue {
         struct cfq_rb_root *service_tree;
         struct cfq_queue *new_cfqq;
         struct cfq_group *cfqg;
-        struct cfq_group *orig_cfqg;
         /* Number of sectors dispatched from queue in single dispatch round */
         unsigned long nr_sectors;
 };
@@ -285,7 +284,6 @@ struct cfq_data {
         unsigned int cfq_slice_idle;
         unsigned int cfq_group_idle;
         unsigned int cfq_latency;
-        unsigned int cfq_group_isolation;
 
         unsigned int cic_index;
         struct list_head cic_list;
@@ -1187,32 +1185,6 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
         int new_cfqq = 1;
         int group_changed = 0;
 
-#ifdef CONFIG_CFQ_GROUP_IOSCHED
-        if (!cfqd->cfq_group_isolation
-            && cfqq_type(cfqq) == SYNC_NOIDLE_WORKLOAD
-            && 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(&cfqq->rb_node))
-                        cfq_group_service_tree_del(cfqd, cfqq->cfqg);
-                cfqq->orig_cfqg = cfqq->cfqg;
-                cfqq->cfqg = &cfqd->root_group;
-                cfqd->root_group.ref++;
-                group_changed = 1;
-        } else if (!cfqd->cfq_group_isolation
-                   && 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(&cfqq->rb_node))
-                        cfq_group_service_tree_del(cfqd, cfqq->cfqg);
-                cfq_put_cfqg(cfqq->cfqg);
-                cfqq->cfqg = cfqq->orig_cfqg;
-                cfqq->orig_cfqg = NULL;
-                group_changed = 1;
-                cfq_log_cfqq(cfqd, cfqq, "moved to origin group");
-        }
-#endif
-
         service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq),
                                                 cfqq_type(cfqq));
         if (cfq_class_idle(cfqq)) {
@@ -2542,7 +2514,7 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
 static void cfq_put_queue(struct cfq_queue *cfqq)
 {
         struct cfq_data *cfqd = cfqq->cfqd;
-        struct cfq_group *cfqg, *orig_cfqg;
+        struct cfq_group *cfqg;
 
         BUG_ON(cfqq->ref <= 0);
 
@@ -2554,7 +2526,6 @@ static void cfq_put_queue(struct cfq_queue *cfqq)
         BUG_ON(rb_first(&cfqq->sort_list));
         BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
         cfqg = cfqq->cfqg;
-        orig_cfqg = cfqq->orig_cfqg;
 
         if (unlikely(cfqd->active_queue == cfqq)) {
                 __cfq_slice_expired(cfqd, cfqq, 0);
@@ -2564,8 +2535,6 @@ static void cfq_put_queue(struct cfq_queue *cfqq)
         BUG_ON(cfq_cfqq_on_rr(cfqq));
         kmem_cache_free(cfq_pool, cfqq);
         cfq_put_cfqg(cfqg);
-        if (orig_cfqg)
-                cfq_put_cfqg(orig_cfqg);
 }
 
 /*
@@ -3953,7 +3922,6 @@ static void *cfq_init_queue(struct request_queue *q)
         cfqd->cfq_slice_idle = cfq_slice_idle;
         cfqd->cfq_group_idle = cfq_group_idle;
         cfqd->cfq_latency = 1;
-        cfqd->cfq_group_isolation = 0;
         cfqd->hw_tag = -1;
         /*
          * we optimistically start assuming sync ops weren't delayed in last
@@ -4029,7 +3997,6 @@ SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
 SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
-SHOW_FUNCTION(cfq_group_isolation_show, cfqd->cfq_group_isolation, 0);
 #undef SHOW_FUNCTION
 
 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
@@ -4063,7 +4030,6 @@ STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
                 UINT_MAX, 0);
 STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
-STORE_FUNCTION(cfq_group_isolation_store, &cfqd->cfq_group_isolation, 0, 1, 0);
 #undef STORE_FUNCTION
 
 #define CFQ_ATTR(name) \
@@ -4081,7 +4047,6 @@ static struct elv_fs_entry cfq_attrs[] = {
         CFQ_ATTR(slice_idle),
         CFQ_ATTR(group_idle),
         CFQ_ATTR(low_latency),
-        CFQ_ATTR(group_isolation),
         __ATTR_NULL
 };