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author | Paolo Valente <paolo.valente@linaro.org> | 2017-07-03 10:00:10 +0200 |
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committer | Jens Axboe <axboe@kernel.dk> | 2017-07-04 00:50:00 +0200 |
commit | 431b17f9d5453533cba7d73e7e40428e4f90b35d (patch) | |
tree | e42cf25bcbfbc315f6b4fc3660dce0890cfdbbe2 /block/bfq-iosched.h | |
parent | Merge branch 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/... (diff) | |
download | linux-431b17f9d5453533cba7d73e7e40428e4f90b35d.tar.xz linux-431b17f9d5453533cba7d73e7e40428e4f90b35d.zip |
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.h | 3 |
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); |