| Message ID | 20210618015922.713999-1-damien.lemoal@wdc.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | block: Remove unnecessary elevator operation checks | expand |
Looks good,
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
On 6/17/21 7:59 PM, Damien Le Moal wrote: > The insert_requests and dispatch_request elevator operations are > mandatory for the correct execution of an elevator, and all implemented > elevators (bfq, kyber and mq-deadline) implement them. As a result, > there is no need to check for these operations before calling them when > a queue has an elevator set. This simplifies the code in > __blk_mq_sched_dispatch_requests() and blk_mq_sched_insert_request(). > > To avoid out-of-tree elevators to crash the kernel in case of bad > implementation, add a check in elv_register() to verify that these > operations are implemented. > > A small, probably not significant, IOPS improvement of 0.1% is observed > with this patch applied (4.117 MIOPS to 4.123 MIOPS, average of 20 fio > runs doing 4K random direct reads with psync and 32 jobs). Applied, thanks.
On 6/17/21 6:59 PM, Damien Le Moal wrote: > The insert_requests and dispatch_request elevator operations are > mandatory for the correct execution of an elevator, and all implemented > elevators (bfq, kyber and mq-deadline) implement them. As a result, > there is no need to check for these operations before calling them when > a queue has an elevator set. This simplifies the code in > __blk_mq_sched_dispatch_requests() and blk_mq_sched_insert_request(). > > To avoid out-of-tree elevators to crash the kernel in case of bad > implementation, add a check in elv_register() to verify that these > operations are implemented. > > A small, probably not significant, IOPS improvement of 0.1% is observed > with this patch applied (4.117 MIOPS to 4.123 MIOPS, average of 20 fio > runs doing 4K random direct reads with psync and 32 jobs). Reviewed-by: Bart Van Assche <bvanassche@acm.org>
diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c index a9182d2f8ad3..bf2c105e81a2 100644 --- a/block/blk-mq-sched.c +++ b/block/blk-mq-sched.c @@ -294,8 +294,7 @@ static int blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx) static int __blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) { struct request_queue *q = hctx->queue; - struct elevator_queue *e = q->elevator; - const bool has_sched_dispatch = e && e->type->ops.dispatch_request; + const bool has_sched = q->elevator; int ret = 0; LIST_HEAD(rq_list); @@ -326,12 +325,12 @@ static int __blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) if (!list_empty(&rq_list)) { blk_mq_sched_mark_restart_hctx(hctx); if (blk_mq_dispatch_rq_list(hctx, &rq_list, 0)) { - if (has_sched_dispatch) + if (has_sched) ret = blk_mq_do_dispatch_sched(hctx); else ret = blk_mq_do_dispatch_ctx(hctx); } - } else if (has_sched_dispatch) { + } else if (has_sched) { ret = blk_mq_do_dispatch_sched(hctx); } else if (hctx->dispatch_busy) { /* dequeue request one by one from sw queue if queue is busy */ @@ -463,7 +462,7 @@ void blk_mq_sched_insert_request(struct request *rq, bool at_head, goto run; } - if (e && e->type->ops.insert_requests) { + if (e) { LIST_HEAD(list); list_add(&rq->queuelist, &list); @@ -494,9 +493,9 @@ void blk_mq_sched_insert_requests(struct blk_mq_hw_ctx *hctx, percpu_ref_get(&q->q_usage_counter); e = hctx->queue->elevator; - if (e && e->type->ops.insert_requests) + if (e) { e->type->ops.insert_requests(hctx, list, false); - else { + } else { /* * try to issue requests directly if the hw queue isn't * busy in case of 'none' scheduler, and this way may save diff --git a/block/elevator.c b/block/elevator.c index 06e203426410..85d0d4adbb64 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -522,6 +522,10 @@ void elv_unregister_queue(struct request_queue *q) int elv_register(struct elevator_type *e) { + /* insert_requests and dispatch_request are mandatory */ + if (WARN_ON_ONCE(!e->ops.insert_requests || !e->ops.dispatch_request)) + return -EINVAL; + /* create icq_cache if requested */ if (e->icq_size) { if (WARN_ON(e->icq_size < sizeof(struct io_cq)) ||
The insert_requests and dispatch_request elevator operations are mandatory for the correct execution of an elevator, and all implemented elevators (bfq, kyber and mq-deadline) implement them. As a result, there is no need to check for these operations before calling them when a queue has an elevator set. This simplifies the code in __blk_mq_sched_dispatch_requests() and blk_mq_sched_insert_request(). To avoid out-of-tree elevators to crash the kernel in case of bad implementation, add a check in elv_register() to verify that these operations are implemented. A small, probably not significant, IOPS improvement of 0.1% is observed with this patch applied (4.117 MIOPS to 4.123 MIOPS, average of 20 fio runs doing 4K random direct reads with psync and 32 jobs). Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> --- block/blk-mq-sched.c | 13 ++++++------- block/elevator.c | 4 ++++ 2 files changed, 10 insertions(+), 7 deletions(-)