On Thu, 2024-08-29 at 05:37 -0600, Jens Axboe wrote: > On 8/29/24 1:18 AM, Tero Kristo wrote: > > diff --git a/block/bio.c b/block/bio.c > > index e9e809a63c59..6c46d75345d7 100644 > > --- a/block/bio.c > > +++ b/block/bio.c > > @@ -282,6 +282,8 @@ void bio_init(struct bio *bio, struct > > block_device *bdev, struct bio_vec *table, > > bio->bi_max_vecs = max_vecs; > > bio->bi_io_vec = table; > > bio->bi_pool = NULL; > > + > > + bdev_update_cpu_latency_pm_qos(bio->bi_bdev); > > } > > EXPORT_SYMBOL(bio_init); > > This is entirely the wrong place to do this, presumably it should be > done at IO dispatch time, not when something initializes a bio. > > And also feels like entirely the wrong way to go about this, adding > overhead to potentially each IO dispatch, of which there can be > millions > per second. Any thoughts where it could/should be added? I moved the bdev_* callback from bio_init to the below location and it seems to work also: diff --git a/block/blk-mq.c b/block/blk-mq.c index 3b4df8e5ac9e..d97a3a4252de 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2706,6 +2706,7 @@ static void __blk_mq_flush_plug_list(struct request_queue *q, { if (blk_queue_quiesced(q)) return; + bdev_update_cpu_latency_pm_qos(q->disk->part0); q->mq_ops->queue_rqs(&plug->mq_list); }