From: Tao Cui Zone append is a primary write operation for zoned devices; zoned btrfs and f2fs use it for data writes. It is priced at zero, so the zone append portion of zoned workloads runs outside the controller: a 1%-weight cgroup issued 16000 appends at zero cost on a zoned null_blk. A zone append advances the zone write pointer and is therefore sequential from the device's perspective; the actual sector is only returned after completion, so the cursor-based seq/rand classification doesn't apply. Price it as a page-counted sequential write. After this patch, 16000 appends from the same cgroup are charged 533264 usec (33us per append). Also skip the cursor update for ZA bios: bi_sector is the zone start, not the actual write position (which is only returned after completion). Setting the cursor from ZA would misclassify subsequent READ/WRITE bios. Fixes: 7caa47151ab2 ("blkcg: implement blk-iocost") Signed-off-by: Tao Cui --- block/blk-iocost.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/block/blk-iocost.c b/block/blk-iocost.c index abc512532ed9..d7860ec1ad49 100644 --- a/block/blk-iocost.c +++ b/block/blk-iocost.c @@ -2557,6 +2557,17 @@ static void calc_vtime_cost_builtin(struct bio *bio, struct ioc_gq *iocg, coef_randio = ioc->params.lcoefs[LCOEF_WRANDIO]; coef_page = ioc->params.lcoefs[LCOEF_WPAGE]; break; + case REQ_OP_ZONE_APPEND: + /* + * A zone append advances the zone write pointer and is + * therefore sequential from the device's perspective, so + * the cursor-based classification below doesn't apply. + * Compute the full cost here. + */ + if (!is_merge) + cost += ioc->params.lcoefs[LCOEF_WSEQIO]; + cost += pages * ioc->params.lcoefs[LCOEF_WPAGE]; + goto out; default: goto out; } @@ -2717,7 +2728,9 @@ static void ioc_rqos_throttle(struct rq_qos *rqos, struct bio *bio) if (!iocg_activate(iocg, &now)) return; - iocg->cursor = bio_end_sector(bio); + /* ZA bi_sector is zone start, not the write position */ + if (bio_op(bio) != REQ_OP_ZONE_APPEND) + iocg->cursor = bio_end_sector(bio); vtime = atomic64_read(&iocg->vtime); cost = adjust_inuse_and_calc_cost(iocg, vtime, abs_cost, &now); -- 2.43.0