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authorPaolo Valente <paolo.valente@linaro.org>2017-07-03 10:00:10 +0200
committerJens Axboe <axboe@kernel.dk>2017-07-03 16:50:00 -0600
commit431b17f9d5453533cba7d73e7e40428e4f90b35d (patch)
treee42cf25bcbfbc315f6b4fc3660dce0890cfdbbe2 /block/bfq-iosched.h
parent7a69f9c60b49699579f5bfb71f928cceba0afe1a (diff)
downloadlinux-431b17f9d5453533cba7d73e7e40428e4f90b35d.tar.bz2
block, bfq: don't change ioprio class for a bfq_queue on a service tree
On each deactivation or re-scheduling (after being served) of a bfq_queue, BFQ invokes the function __bfq_entity_update_weight_prio(), to perform pending updates of ioprio, weight and ioprio class for the bfq_queue. BFQ also invokes this function on I/O-request dispatches, to raise or lower weights more quickly when needed, thereby improving latency. However, the entity representing the bfq_queue may be on the active (sub)tree of a service tree when this happens, and, although with a very low probability, the bfq_queue may happen to also have a pending change of its ioprio class. If both conditions hold when __bfq_entity_update_weight_prio() is invoked, then the entity moves to a sort of hybrid state: the new service tree for the entity, as returned by bfq_entity_service_tree(), differs from service tree on which the entity still is. The functions that handle activations and deactivations of entities do not cope with such a hybrid state (and would need to become more complex to cope). This commit addresses this issue by just making __bfq_entity_update_weight_prio() not perform also a possible pending change of ioprio class, when invoked on an I/O-request dispatch for a bfq_queue. Such a change is thus postponed to when __bfq_entity_update_weight_prio() is invoked on deactivation or re-scheduling of the bfq_queue. Reported-by: Marco Piazza <mpiazza@gmail.com> Reported-by: Laurentiu Nicola <lnicola@dend.ro> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Tested-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/bfq-iosched.h')
-rw-r--r--block/bfq-iosched.h3
1 files changed, 2 insertions, 1 deletions
diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
index 5c3bf9861492..8fd83b885774 100644
--- a/block/bfq-iosched.h
+++ b/block/bfq-iosched.h
@@ -892,7 +892,8 @@ void bfq_put_idle_entity(struct bfq_service_tree *st,
struct bfq_entity *entity);
struct bfq_service_tree *
__bfq_entity_update_weight_prio(struct bfq_service_tree *old_st,
- struct bfq_entity *entity);
+ struct bfq_entity *entity,
+ bool update_class_too);
void bfq_bfqq_served(struct bfq_queue *bfqq, int served);
void bfq_bfqq_charge_time(struct bfq_data *bfqd, struct bfq_queue *bfqq,
unsigned long time_ms);