On 4/26/21 10:00 AM, Ming Lei wrote: > On Mon, Apr 26, 2021 at 09:19:20AM +0200, Hannes Reinecke wrote: >> On 4/22/21 2:20 PM, Ming Lei wrote: >>> Limit at most 8 queues are polled in each blk_pull(), avoid to >>> add extra latency when queue depth is high. >>> >>> Reviewed-by: Jeffle Xu <[email protected]> >>> Signed-off-by: Ming Lei <[email protected]> >>> --- >>> block/blk-poll.c | 78 ++++++++++++++++++++++++++++++++++-------------- >>> 1 file changed, 55 insertions(+), 23 deletions(-) >>> >>> diff --git a/block/blk-poll.c b/block/blk-poll.c >>> index 249d73ff6f81..20e7c47cc984 100644 >>> --- a/block/blk-poll.c >>> +++ b/block/blk-poll.c >>> @@ -288,36 +288,32 @@ static void bio_grp_list_move(struct bio_grp_list >>> *dst, >>> src->nr_grps -= cnt; >>> } >>> >>> -static int blk_mq_poll_io(struct bio *bio) >>> +#define POLL_HCTX_MAX_CNT 8 >>> + >>> +static bool blk_add_unique_hctx(struct blk_mq_hw_ctx **data, int *cnt, >>> + struct blk_mq_hw_ctx *hctx) >>> { >>> - struct request_queue *q = bio->bi_bdev->bd_disk->queue; >>> - blk_qc_t cookie = bio_get_poll_data(bio); >>> - int ret = 0; >>> + int i; >>> >>> - /* wait until the bio is submitted really */ >>> - if (!blk_qc_t_ready(cookie)) >>> - return 0; >>> >>> - if (!bio_flagged(bio, BIO_DONE) && blk_qc_t_valid(cookie)) { >>> - struct blk_mq_hw_ctx *hctx = >>> - q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)]; >>> + for (i = 0; i < *cnt; i++) { >>> + if (data[i] == hctx) >>> + goto exit; >>> + } >>> >>> - ret += blk_mq_poll_hctx(q, hctx); >>> + if (i < POLL_HCTX_MAX_CNT) { >>> + data[i] = hctx; >>> + (*cnt)++; >>> } >>> - return ret; >>> + exit: >>> + return *cnt == POLL_HCTX_MAX_CNT; >>> } >>> >>> -static int blk_bio_poll_and_end_io(struct bio_grp_list *grps) >>> +static void blk_build_poll_queues(struct bio_grp_list *grps, >>> + struct blk_mq_hw_ctx **data, int *cnt) >>> { >>> - int ret = 0; >>> int i; >>> >>> - /* >>> - * Poll hw queue first. >>> - * >>> - * TODO: limit max poll times and make sure to not poll same >>> - * hw queue one more time. >>> - */ >>> for (i = 0; i < grps->nr_grps; i++) { >>> struct bio_grp_list_data *grp = &grps->head[i]; >>> struct bio *bio; >>> @@ -325,11 +321,31 @@ static int blk_bio_poll_and_end_io(struct >>> bio_grp_list *grps) >>> if (bio_grp_list_grp_empty(grp)) >>> continue; >>> >>> - for (bio = grp->list.head; bio; bio = bio->bi_poll) >>> - ret += blk_mq_poll_io(bio); >>> + for (bio = grp->list.head; bio; bio = bio->bi_poll) { >>> + blk_qc_t cookie; >>> + struct blk_mq_hw_ctx *hctx; >>> + struct request_queue *q; >>> + >>> + if (bio_flagged(bio, BIO_DONE)) >>> + continue; >>> + >>> + /* wait until the bio is submitted really */ >>> + cookie = bio_get_poll_data(bio); >>> + if (!blk_qc_t_ready(cookie) || !blk_qc_t_valid(cookie)) >>> + continue; >>> + >>> + q = bio->bi_bdev->bd_disk->queue; >>> + hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)]; >>> + if (blk_add_unique_hctx(data, cnt, hctx)) >>> + return; >>> + } >>> } >>> +} >>> + >>> +static void blk_bio_poll_reap_ios(struct bio_grp_list *grps) >>> +{ >>> + int i; >>> >>> - /* reap bios */ >>> for (i = 0; i < grps->nr_grps; i++) { >>> struct bio_grp_list_data *grp = &grps->head[i]; >>> struct bio *bio; >>> @@ -354,6 +370,22 @@ static int blk_bio_poll_and_end_io(struct bio_grp_list >>> *grps) >>> } >>> __bio_grp_list_merge(&grp->list, &bl); >>> } >>> +} >>> + >>> +static int blk_bio_poll_and_end_io(struct bio_grp_list *grps) >>> +{ >>> + int ret = 0; >>> + int i; >>> + struct blk_mq_hw_ctx *hctx[POLL_HCTX_MAX_CNT]; >>> + int cnt = 0; >>> + >>> + blk_build_poll_queues(grps, hctx, &cnt); >>> + >>> + for (i = 0; i < cnt; i++) >>> + ret += blk_mq_poll_hctx(hctx[i]->queue, hctx[i]); >>> + >>> + blk_bio_poll_reap_ios(grps); >>> + >>> return ret; >>> } >>> >>> >> Can't we make it a sysfs attribute instead of hard-coding it? >> '8' seems a bit arbitrary to me, I'd rather have the ability to modify it... > > I'd rather not add such code in the feature 'enablement' stage since I doesn't > observe the number plays a big role yet. It is added for holding hw queues to > be polled on stack variables, also avoid to add too much latency if there is > too many bios from too many hw queues to be reaped. > > Also the actual polled hw queues can be observed easily via bpftrace, so debug > purpose from sysfs isn't necessary too. > Okay. You can add my
Reviewed-by: Hannes Reinecke <[email protected]> Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect [email protected] +49 911 74053 688 SUSE Software Solutions Germany GmbH, 90409 Nürnberg GF: F. Imendörffer, HRB 36809 (AG Nürnberg) -- dm-devel mailing list [email protected] https://listman.redhat.com/mailman/listinfo/dm-devel
