* [PATCH v6] block: plug attempts to batch allocate tags multiple times [not found] <CGME20251117085321epcas5p3de0647f01a818db024bea32870f223f4@epcas5p3.samsung.com> @ 2025-11-17 8:48 ` Xue He 2025-11-17 10:19 ` Ming Lei 0 siblings, 1 reply; 3+ messages in thread From: Xue He @ 2025-11-17 8:48 UTC (permalink / raw) To: axboe, ming.lei; +Cc: linux-block, linux-kernel, yukuai, hexue This patch aims to enable batch allocation of sufficient tags after batch IO submission with plug mechanism, thereby avoiding the need for frequent individual requests when the initial allocation is insufficient. ----------------------------------------------------------- HW: 16 CPUs/16 poll queues Disk: Samsung PM9A3 Gen4 3.84T CMD: [global] ioengine=io_uring group_reporting=1 time_based=1 runtime=1m refill_buffers=1 norandommap=1 randrepeat=0 fixedbufs=1 registerfiles=1 rw=randread iodepth=128 iodepth_batch_submit=32 iodepth_batch_complete_min=32 iodepth_batch_complete_max=128 iodepth_low=32 bs=4k numjobs=1 direct=1 hipri=1 [job1] filename=/dev/nvme0n1 name=batch_test ------------------------------------------------------------ Perf: base code: __blk_mq_alloc_requests() 1.47% patch: __blk_mq_alloc_requests() 0.78% ------------------------------------------------------------ --- changes since v1: - Modify multiple batch registrations into a single loop to achieve the batch quantity changes since v2: - Modify the call location of remainder handling - Refactoring sbitmap cleanup time changes since v3: - Add handle operation in loop - Add helper sbitmap_find_bits_in_word changes since v4: - Split blk-mq.c changes from sbitmap changes since v5: - Add workload with perf - Modify over-counting bug Signed-off-by: hexue <xue01.he@samsung.com> --- block/blk-mq.c | 39 ++++++++++++++++++++++----------------- 1 file changed, 22 insertions(+), 17 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index d626d32f6e57..9e6fca1b5fb7 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -467,26 +467,31 @@ __blk_mq_alloc_requests_batch(struct blk_mq_alloc_data *data) unsigned long tag_mask; int i, nr = 0; - tag_mask = blk_mq_get_tags(data, data->nr_tags, &tag_offset); - if (unlikely(!tag_mask)) - return NULL; + do { + tag_mask = blk_mq_get_tags(data, data->nr_tags, &tag_offset); + if (unlikely(!tag_mask)) { + if (nr == 0) + return NULL; + break; + } + tags = blk_mq_tags_from_data(data); + for (i = 0; tag_mask; i++) { + if (!(tag_mask & (1UL << i))) + continue; + tag = tag_offset + i; + prefetch(tags->static_rqs[tag]); + tag_mask &= ~(1UL << i); + rq = blk_mq_rq_ctx_init(data, tags, tag); + rq_list_add_head(data->cached_rqs, rq); + data->nr_tags--; + nr++; + } + } while (data->nr_tags); - tags = blk_mq_tags_from_data(data); - for (i = 0; tag_mask; i++) { - if (!(tag_mask & (1UL << i))) - continue; - tag = tag_offset + i; - prefetch(tags->static_rqs[tag]); - tag_mask &= ~(1UL << i); - rq = blk_mq_rq_ctx_init(data, tags, tag); - rq_list_add_head(data->cached_rqs, rq); - nr++; - } - if (!(data->rq_flags & RQF_SCHED_TAGS)) - blk_mq_add_active_requests(data->hctx, nr); /* caller already holds a reference, add for remainder */ percpu_ref_get_many(&data->q->q_usage_counter, nr - 1); - data->nr_tags -= nr; + if (!(data->rq_flags & RQF_SCHED_TAGS)) + blk_mq_add_active_requests(data->hctx, nr); return rq_list_pop(data->cached_rqs); } -- 2.34.1 ^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v6] block: plug attempts to batch allocate tags multiple times 2025-11-17 8:48 ` [PATCH v6] block: plug attempts to batch allocate tags multiple times Xue He @ 2025-11-17 10:19 ` Ming Lei 2025-11-17 10:22 ` Xue He 0 siblings, 1 reply; 3+ messages in thread From: Ming Lei @ 2025-11-17 10:19 UTC (permalink / raw) To: Xue He; +Cc: axboe, linux-block, linux-kernel, yukuai On Mon, Nov 17, 2025 at 08:48:45AM +0000, Xue He wrote: > This patch aims to enable batch allocation of sufficient tags after > batch IO submission with plug mechanism, thereby avoiding the need for > frequent individual requests when the initial allocation is > insufficient. > ----------------------------------------------------------- > HW: > 16 CPUs/16 poll queues > Disk: Samsung PM9A3 Gen4 3.84T > > CMD: > [global] > ioengine=io_uring > group_reporting=1 > time_based=1 > runtime=1m > refill_buffers=1 > norandommap=1 > randrepeat=0 > fixedbufs=1 > registerfiles=1 > rw=randread > iodepth=128 > iodepth_batch_submit=32 > iodepth_batch_complete_min=32 > iodepth_batch_complete_max=128 > iodepth_low=32 > bs=4k > numjobs=1 > direct=1 > hipri=1 > > [job1] > filename=/dev/nvme0n1 > name=batch_test > ------------------------------------------------------------ > Perf: > base code: __blk_mq_alloc_requests() 1.47% > patch: __blk_mq_alloc_requests() 0.78% > ------------------------------------------------------------ > > --- > changes since v1: > - Modify multiple batch registrations into a single loop to achieve > the batch quantity > > changes since v2: > - Modify the call location of remainder handling > - Refactoring sbitmap cleanup time > > changes since v3: > - Add handle operation in loop > - Add helper sbitmap_find_bits_in_word > > changes since v4: > - Split blk-mq.c changes from sbitmap > > changes since v5: > - Add workload with perf > - Modify over-counting bug > > Signed-off-by: hexue <xue01.he@samsung.com> > --- > block/blk-mq.c | 39 ++++++++++++++++++++++----------------- > 1 file changed, 22 insertions(+), 17 deletions(-) > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index d626d32f6e57..9e6fca1b5fb7 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -467,26 +467,31 @@ __blk_mq_alloc_requests_batch(struct blk_mq_alloc_data *data) > unsigned long tag_mask; > int i, nr = 0; > > - tag_mask = blk_mq_get_tags(data, data->nr_tags, &tag_offset); > - if (unlikely(!tag_mask)) > - return NULL; > + do { > + tag_mask = blk_mq_get_tags(data, data->nr_tags, &tag_offset); You may keep the original batch update on `data->nr_tags` by passing `data->nr_tags - nr`. > + if (unlikely(!tag_mask)) { > + if (nr == 0) > + return NULL; > + break; > + } > + tags = blk_mq_tags_from_data(data); > + for (i = 0; tag_mask; i++) { > + if (!(tag_mask & (1UL << i))) > + continue; > + tag = tag_offset + i; > + prefetch(tags->static_rqs[tag]); > + tag_mask &= ~(1UL << i); > + rq = blk_mq_rq_ctx_init(data, tags, tag); > + rq_list_add_head(data->cached_rqs, rq); > + data->nr_tags--; data->nr_tags-- can be killed. > + nr++; > + } > + } while (data->nr_tags); Replace the above check with `data->nr_tags > nr` > > - tags = blk_mq_tags_from_data(data); > - for (i = 0; tag_mask; i++) { > - if (!(tag_mask & (1UL << i))) > - continue; > - tag = tag_offset + i; > - prefetch(tags->static_rqs[tag]); > - tag_mask &= ~(1UL << i); > - rq = blk_mq_rq_ctx_init(data, tags, tag); > - rq_list_add_head(data->cached_rqs, rq); > - nr++; > - } > - if (!(data->rq_flags & RQF_SCHED_TAGS)) > - blk_mq_add_active_requests(data->hctx, nr); > /* caller already holds a reference, add for remainder */ > percpu_ref_get_many(&data->q->q_usage_counter, nr - 1); > - data->nr_tags -= nr; The above line needs to keep. > + if (!(data->rq_flags & RQF_SCHED_TAGS)) > + blk_mq_add_active_requests(data->hctx, nr); The above two lines can be kept in original position, then the change outside loop can be avoided. With above update, feel free to add: Reviewed-by: Ming Lei <ming.lei@redhat.com> Thanks, Ming ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v6] block: plug attempts to batch allocate tags multiple times 2025-11-17 10:19 ` Ming Lei @ 2025-11-17 10:22 ` Xue He 0 siblings, 0 replies; 3+ messages in thread From: Xue He @ 2025-11-17 10:22 UTC (permalink / raw) To: ming.lei; +Cc: axboe, linux-block, linux-kernel, xue01.he, yukuai >The above two lines can be kept in original position, then the change >outside loop can be avoided. > >With above update, feel free to add: > >Reviewed-by: Ming Lei <ming.lei@redhat.com> > >Thanks, >Ming Thanks for review, I'll update and add this, then resubmit v7. Thanks, Xue He ^ permalink raw reply [flat|nested] 3+ messages in thread
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2025-11-17 8:48 ` [PATCH v6] block: plug attempts to batch allocate tags multiple times Xue He
2025-11-17 10:19 ` Ming Lei
2025-11-17 10:22 ` Xue He
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