path: root/block/Kconfig.iosched
diff options
authorArianna Avanzini <>2017-04-12 18:23:08 +0200
committerJens Axboe <>2017-04-19 08:30:26 -0600
commite21b7a0b988772e82e7147e1c659a5afe2ae003c (patch)
treea3958b4ce872269fcbdabf4f20c40b1c7c181de5 /block/Kconfig.iosched
parentaee69d78dec0ffdf82e35d57c626e80dddc314d5 (diff)
block, bfq: add full hierarchical scheduling and cgroups support
Add complete support for full hierarchical scheduling, with a cgroups interface. Full hierarchical scheduling is implemented through the 'entity' abstraction: both bfq_queues, i.e., the internal BFQ queues associated with processes, and groups are represented in general by entities. Given the bfq_queues associated with the processes belonging to a given group, the entities representing these queues are sons of the entity representing the group. At higher levels, if a group, say G, contains other groups, then the entity representing G is the parent entity of the entities representing the groups in G. Hierarchical scheduling is performed as follows: if the timestamps of a leaf entity (i.e., of a bfq_queue) change, and such a change lets the entity become the next-to-serve entity for its parent entity, then the timestamps of the parent entity are recomputed as a function of the budget of its new next-to-serve leaf entity. If the parent entity belongs, in its turn, to a group, and its new timestamps let it become the next-to-serve for its parent entity, then the timestamps of the latter parent entity are recomputed as well, and so on. When a new bfq_queue must be set in service, the reverse path is followed: the next-to-serve highest-level entity is chosen, then its next-to-serve child entity, and so on, until the next-to-serve leaf entity is reached, and the bfq_queue that this entity represents is set in service. Writeback is accounted for on a per-group basis, i.e., for each group, the async I/O requests of the processes of the group are enqueued in a distinct bfq_queue, and the entity associated with this queue is a child of the entity associated with the group. Weights can be assigned explicitly to groups and processes through the cgroups interface, differently from what happens, for single processes, if the cgroups interface is not used (as explained in the description of the previous patch). In particular, since each node has a full scheduler, each group can be assigned its own weight. Signed-off-by: Fabio Checconi <> Signed-off-by: Paolo Valente <> Signed-off-by: Arianna Avanzini <> Signed-off-by: Jens Axboe <>
Diffstat (limited to 'block/Kconfig.iosched')
1 files changed, 10 insertions, 0 deletions
diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
index 6fc3602..fd2cefa 100644
--- a/block/Kconfig.iosched
+++ b/block/Kconfig.iosched
@@ -40,6 +40,7 @@ config CFQ_GROUP_IOSCHED
Enable group IO scheduling in CFQ.
prompt "Default I/O scheduler"
@@ -89,6 +90,15 @@ config IOSCHED_BFQ
real-time applications. Details in
+ bool "BFQ hierarchical scheduling support"
+ depends on IOSCHED_BFQ && BLK_CGROUP
+ default n
+ ---help---
+ Enable hierarchical scheduling in BFQ, using the blkio
+ (cgroups-v1) or io (cgroups-v2) controller.