On Tue, Nov 19, 2019 at 10:27:36PM +0800, John Garry wrote: > Some SCSI HBAs (such as HPSA, megaraid, mpt3sas, hisi_sas_v3 ..) support > multiple reply queues with single hostwide tags. > > In addition, these drivers want to use interrupt assignment in > pci_alloc_irq_vectors(PCI_IRQ_AFFINITY). However, as discussed in [0], > CPU hotplug may cause in-flight IO completion to not be serviced when an > interrupt is shutdown. > > To solve that problem, Ming's patchset to drain hctx's should ensure no > IOs are missed in-flight [1]. > > However, to take advantage of that patchset, we need to map the HBA HW > queues to blk mq hctx's; to do that, we need to expose the HBA HW queues. > > In making that transition, the per-SCSI command request tags are no > longer unique per Scsi host - they are just unique per hctx. As such, the > HBA LLDD would have to generate this tag internally, which has a certain > performance overhead. > > However another problem is that blk mq assumes the host may accept > (Scsi_host.can_queue * #hw queue) commands. In [2], we removed the Scsi > host busy counter, which would stop the LLDD being sent more than > .can_queue commands; however, we should still ensure that the block layer > does not issue more than .can_queue commands to the Scsi host. > > To solve this problem, introduce a shared sbitmap per blk_mq_tag_set, > which may be requested at init time. > > New flag BLK_MQ_F_TAG_HCTX_SHARED should be set when requesting the > tagset to indicate whether the shared sbitmap should be used. > > Even when BLK_MQ_F_TAG_HCTX_SHARED is set, we still allocate a full set of > tags and requests per hctx; the reason for this is that if we only allocate > tags and requests for a single hctx - like hctx0 - we may break block > drivers which expect a request be associated with a specific hctx, i.e. > not hctx0. > > This is based on work originally from Ming Lei in [3] and from Bart's > suggestion in [4]. > > [0] https://lore.kernel.org/linux-block/alpine.DEB.2.21.1904051331270.1802@xxxxxxxxxxxxxxxxxxxxxxx/ > [1] https://lore.kernel.org/linux-block/20191014015043.25029-1-ming.lei@xxxxxxxxxx/ > [2] https://lore.kernel.org/linux-scsi/20191025065855.6309-1-ming.lei@xxxxxxxxxx/ > [3] https://lore.kernel.org/linux-block/20190531022801.10003-1-ming.lei@xxxxxxxxxx/ > [4] https://lore.kernel.org/linux-block/ff77beff-5fd9-9f05-12b6-826922bace1f@xxxxxxxxxx/T/#m3db0a602f095cbcbff27e9c884d6b4ae826144be > > Signed-off-by: John Garry <john.garry@xxxxxxxxxx> > --- > block/bfq-iosched.c | 4 +-- > block/blk-mq-debugfs.c | 4 +-- > block/blk-mq-sched.c | 14 ++++++++ > block/blk-mq-tag.c | 74 +++++++++++++++++++++++++++++++++--------- > block/blk-mq-tag.h | 15 +++++++-- > block/blk-mq.c | 57 +++++++++++++++++++++++++++++--- > block/blk-mq.h | 5 +++ > block/kyber-iosched.c | 4 +-- > include/linux/blk-mq.h | 7 ++++ > 9 files changed, 157 insertions(+), 27 deletions(-) > > diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c > index 0319d6339822..9633c864af07 100644 > --- a/block/bfq-iosched.c > +++ b/block/bfq-iosched.c > @@ -6327,8 +6327,8 @@ static void bfq_depth_updated(struct blk_mq_hw_ctx *hctx) > struct blk_mq_tags *tags = hctx->sched_tags; > unsigned int min_shallow; > > - min_shallow = bfq_update_depths(bfqd, &tags->bitmap_tags); > - sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, min_shallow); > + min_shallow = bfq_update_depths(bfqd, tags->pbitmap_tags); > + sbitmap_queue_min_shallow_depth(tags->pbitmap_tags, min_shallow); > } > > static int bfq_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int index) > diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c > index 33a40ae1d60f..9cf2f09c08e4 100644 > --- a/block/blk-mq-debugfs.c > +++ b/block/blk-mq-debugfs.c > @@ -483,7 +483,7 @@ static int hctx_tags_bitmap_show(void *data, struct seq_file *m) > res = mutex_lock_interruptible(&q->sysfs_lock); > if (res) > goto out; > - if (hctx->tags) > + if (hctx->tags) /* We should just iterate the relevant bits for this hctx FIXME */ > sbitmap_bitmap_show(&hctx->tags->bitmap_tags.sb, m); > mutex_unlock(&q->sysfs_lock); > > @@ -517,7 +517,7 @@ static int hctx_sched_tags_bitmap_show(void *data, struct seq_file *m) > res = mutex_lock_interruptible(&q->sysfs_lock); > if (res) > goto out; > - if (hctx->sched_tags) > + if (hctx->sched_tags) /* We should just iterate the relevant bits for this hctx FIXME */ > sbitmap_bitmap_show(&hctx->sched_tags->bitmap_tags.sb, m); > mutex_unlock(&q->sysfs_lock); > > diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c > index ca22afd47b3d..b23547f10949 100644 > --- a/block/blk-mq-sched.c > +++ b/block/blk-mq-sched.c > @@ -492,6 +492,7 @@ static void blk_mq_sched_tags_teardown(struct request_queue *q) > > int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e) > { > + struct blk_mq_tag_set *tag_set = q->tag_set; > struct blk_mq_hw_ctx *hctx; > struct elevator_queue *eq; > unsigned int i; > @@ -537,6 +538,19 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e) > blk_mq_debugfs_register_sched_hctx(q, hctx); > } > > + if (blk_mq_is_sbitmap_shared(tag_set)) { > + if (!blk_mq_init_sched_shared_sbitmap(tag_set, q->nr_requests)) { > + ret = -ENOMEM; > + goto err; > + } > + queue_for_each_hw_ctx(q, hctx, i) { > + struct blk_mq_tags *tags = hctx->sched_tags; > + > + tags->pbitmap_tags = &tag_set->sched_shared_bitmap_tags; > + tags->pbreserved_tags = &tag_set->sched_shared_breserved_tags; This kind of sharing is wrong, sched tags should be request queue wide instead of tagset wide, and each request queue has its own & independent scheduler queue. > + } > + } > + > return 0; > > err: > diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c > index 42792942b428..6625bebb46c3 100644 > --- a/block/blk-mq-tag.c > +++ b/block/blk-mq-tag.c > @@ -35,9 +35,9 @@ bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx) > */ > void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool include_reserve) > { > - sbitmap_queue_wake_all(&tags->bitmap_tags); > + sbitmap_queue_wake_all(tags->pbitmap_tags); > if (include_reserve) > - sbitmap_queue_wake_all(&tags->breserved_tags); > + sbitmap_queue_wake_all(tags->pbreserved_tags); > } > > /* > @@ -113,10 +113,10 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data) > WARN_ON_ONCE(1); > return BLK_MQ_TAG_FAIL; > } > - bt = &tags->breserved_tags; > + bt = tags->pbreserved_tags; > tag_offset = 0; > } else { > - bt = &tags->bitmap_tags; > + bt = tags->pbitmap_tags; > tag_offset = tags->nr_reserved_tags; > } > > @@ -162,9 +162,9 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data) > data->ctx); > tags = blk_mq_tags_from_data(data); > if (data->flags & BLK_MQ_REQ_RESERVED) > - bt = &tags->breserved_tags; > + bt = tags->pbreserved_tags; > else > - bt = &tags->bitmap_tags; > + bt = tags->pbitmap_tags; > > /* > * If destination hw queue is changed, fake wake up on > @@ -190,10 +190,10 @@ void blk_mq_put_tag(struct blk_mq_tags *tags, struct blk_mq_ctx *ctx, > const int real_tag = tag - tags->nr_reserved_tags; > > BUG_ON(real_tag >= tags->nr_tags); > - sbitmap_queue_clear(&tags->bitmap_tags, real_tag, ctx->cpu); > + sbitmap_queue_clear(tags->pbitmap_tags, real_tag, ctx->cpu); > } else { > BUG_ON(tag >= tags->nr_reserved_tags); > - sbitmap_queue_clear(&tags->breserved_tags, tag, ctx->cpu); > + sbitmap_queue_clear(tags->pbreserved_tags, tag, ctx->cpu); > } > } > > @@ -220,7 +220,7 @@ static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data) > * We can hit rq == NULL here, because the tagging functions > * test and set the bit before assigning ->rqs[]. > */ > - if (rq && rq->q == hctx->queue) > + if (rq && rq->q == hctx->queue && rq->mq_hctx == hctx) > return iter_data->fn(hctx, rq, iter_data->data, reserved); > return true; > } > @@ -321,8 +321,8 @@ static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags, > busy_tag_iter_fn *fn, void *priv) > { > if (tags->nr_reserved_tags) > - bt_tags_for_each(tags, &tags->breserved_tags, fn, priv, true); > - bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, false); > + bt_tags_for_each(tags, tags->pbreserved_tags, fn, priv, true); > + bt_tags_for_each(tags, tags->pbitmap_tags, fn, priv, false); > } > > /** > @@ -419,8 +419,8 @@ void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn, > continue; > > if (tags->nr_reserved_tags) > - bt_for_each(hctx, &tags->breserved_tags, fn, priv, true); > - bt_for_each(hctx, &tags->bitmap_tags, fn, priv, false); > + bt_for_each(hctx, tags->pbreserved_tags, fn, priv, true); > + bt_for_each(hctx, tags->pbitmap_tags, fn, priv, false); > } > blk_queue_exit(q); > } > @@ -444,6 +444,9 @@ static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags, > node)) > goto free_bitmap_tags; > > + tags->pbitmap_tags = &tags->bitmap_tags; > + tags->pbreserved_tags = &tags->breserved_tags; > + > return tags; > free_bitmap_tags: > sbitmap_queue_free(&tags->bitmap_tags); > @@ -452,7 +455,46 @@ static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags, > return NULL; > } > > -struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags, > +bool blk_mq_init_shared_sbitmap(struct blk_mq_tag_set *tag_set) > +{ > + unsigned int depth = tag_set->queue_depth -tag_set->reserved_tags; > + int alloc_policy = BLK_MQ_FLAG_TO_ALLOC_POLICY(tag_set->flags); > + bool round_robin = alloc_policy == BLK_TAG_ALLOC_RR; > + int node = tag_set->numa_node; > + > + if (bt_alloc(&tag_set->shared_bitmap_tags, depth, round_robin, node)) > + return false; > + if (bt_alloc(&tag_set->shared_breserved_tags, tag_set->reserved_tags, round_robin, > + node)) > + goto free_bitmap_tags; > + > + return true; > +free_bitmap_tags: > + sbitmap_queue_free(&tag_set->shared_bitmap_tags); > + return false; > +} > + > +bool blk_mq_init_sched_shared_sbitmap(struct blk_mq_tag_set *tag_set, unsigned long nr_requests) > +{ > + unsigned int depth = nr_requests -tag_set->reserved_tags; > + int alloc_policy = BLK_MQ_FLAG_TO_ALLOC_POLICY(tag_set->flags); > + bool round_robin = alloc_policy == BLK_TAG_ALLOC_RR; > + int node = tag_set->numa_node; > + > + if (bt_alloc(&tag_set->sched_shared_bitmap_tags, depth, round_robin, node)) > + return false; > + if (bt_alloc(&tag_set->sched_shared_breserved_tags, tag_set->reserved_tags, round_robin, > + node)) > + goto free_bitmap_tags; > + > + return true; > +free_bitmap_tags: > + sbitmap_queue_free(&tag_set->sched_shared_bitmap_tags); > + return false; > +} > + > +struct blk_mq_tags *blk_mq_init_tags(struct blk_mq_tag_set *set, > + unsigned int total_tags, > unsigned int reserved_tags, > int node, int alloc_policy) > { > @@ -470,6 +512,8 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags, > tags->nr_tags = total_tags; > tags->nr_reserved_tags = reserved_tags; > > + if (blk_mq_is_sbitmap_shared(set)) > + return tags; > return blk_mq_init_bitmap_tags(tags, node, alloc_policy); > } > > @@ -526,7 +570,7 @@ int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx, > * Don't need (or can't) update reserved tags here, they > * remain static and should never need resizing. > */ > - sbitmap_queue_resize(&tags->bitmap_tags, > + sbitmap_queue_resize(tags->pbitmap_tags, > tdepth - tags->nr_reserved_tags); > } > > diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h > index e36bec8e0970..198b6fbe2c22 100644 > --- a/block/blk-mq-tag.h > +++ b/block/blk-mq-tag.h > @@ -13,20 +13,31 @@ struct blk_mq_tags { > > atomic_t active_queues; > > + /* We should consider deleting these so they are not referenced by mistake */ > struct sbitmap_queue bitmap_tags; > struct sbitmap_queue breserved_tags; > > + struct sbitmap_queue *pbitmap_tags; > + struct sbitmap_queue *pbreserved_tags; > + > struct request **rqs; > struct request **static_rqs; > struct list_head page_list; > }; > > > -extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags, unsigned int reserved_tags, int node, int alloc_policy); > +extern bool blk_mq_init_shared_sbitmap(struct blk_mq_tag_set *tag_set); > +extern bool blk_mq_init_sched_shared_sbitmap(struct blk_mq_tag_set *tag_set, > + unsigned long nr_requests); > +extern struct blk_mq_tags *blk_mq_init_tags(struct blk_mq_tag_set *tag_set, > + unsigned int nr_tags, > + unsigned int reserved_tags, > + int node, int alloc_policy); > extern void blk_mq_free_tags(struct blk_mq_tags *tags); > > extern unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data); > -extern void blk_mq_put_tag(struct blk_mq_tags *tags, struct blk_mq_ctx *ctx, unsigned int tag); > +extern void blk_mq_put_tag(struct blk_mq_tags *tags, > + struct blk_mq_ctx *ctx, unsigned int tag); > extern int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx, > struct blk_mq_tags **tags, > unsigned int depth, bool can_grow); > diff --git a/block/blk-mq.c b/block/blk-mq.c > index 2d2956249ae9..8d5b21919c9a 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -1089,7 +1089,7 @@ static int blk_mq_dispatch_wake(wait_queue_entry_t *wait, unsigned mode, > struct sbitmap_queue *sbq; > > list_del_init(&wait->entry); > - sbq = &hctx->tags->bitmap_tags; > + sbq = hctx->tags->pbitmap_tags; > atomic_dec(&sbq->ws_active); > } > spin_unlock(&hctx->dispatch_wait_lock); > @@ -1107,7 +1107,7 @@ static int blk_mq_dispatch_wake(wait_queue_entry_t *wait, unsigned mode, > static bool blk_mq_mark_tag_wait(struct blk_mq_hw_ctx *hctx, > struct request *rq) > { > - struct sbitmap_queue *sbq = &hctx->tags->bitmap_tags; > + struct sbitmap_queue *sbq = hctx->tags->pbitmap_tags; > struct wait_queue_head *wq; > wait_queue_entry_t *wait; > bool ret; > @@ -2097,7 +2097,7 @@ struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set, > if (node == NUMA_NO_NODE) > node = set->numa_node; > > - tags = blk_mq_init_tags(nr_tags, reserved_tags, node, > + tags = blk_mq_init_tags(set, nr_tags, reserved_tags, node, > BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags)); > if (!tags) > return NULL; > @@ -3100,6 +3100,20 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set) > if (ret) > goto out_free_mq_map; > > + if (blk_mq_is_sbitmap_shared(set)) { > + if (!blk_mq_init_shared_sbitmap(set)) { > + ret = -ENOMEM; > + goto out_free_mq_map; > + } > + > + for (i = 0; i < set->nr_hw_queues; i++) { > + struct blk_mq_tags *tags = set->tags[i]; > + > + tags->pbitmap_tags = &set->shared_bitmap_tags; > + tags->pbreserved_tags = &set->shared_breserved_tags; > + } > + } > + > mutex_init(&set->tag_list_lock); > INIT_LIST_HEAD(&set->tag_list); > > @@ -3137,6 +3151,7 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr) > { > struct blk_mq_tag_set *set = q->tag_set; > struct blk_mq_hw_ctx *hctx; > + bool sched_tags = false; > int i, ret; > > if (!set) > @@ -3160,6 +3175,7 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr) > ret = blk_mq_tag_update_depth(hctx, &hctx->tags, nr, > false); > } else { > + sched_tags = true; > ret = blk_mq_tag_update_depth(hctx, &hctx->sched_tags, > nr, true); > } > @@ -3169,8 +3185,41 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr) > q->elevator->type->ops.depth_updated(hctx); > } > > - if (!ret) > + /* > + * if ret is 0, all queues should have been updated to the same depth > + * if not, then maybe some have been updated - yuk, need to handle this for shared sbitmap... > + * if some are updated, we should probably roll back the change altogether. FIXME > + */ > + if (!ret) { > + if (blk_mq_is_sbitmap_shared(set)) { > + if (sched_tags) { > + sbitmap_queue_free(&set->sched_shared_bitmap_tags); > + sbitmap_queue_free(&set->sched_shared_breserved_tags); > + if (!blk_mq_init_sched_shared_sbitmap(set, nr)) > + return -ENOMEM; /* fixup error handling */ > + > + queue_for_each_hw_ctx(q, hctx, i) { > + hctx->sched_tags->pbitmap_tags = &set->sched_shared_bitmap_tags; > + hctx->sched_tags->pbreserved_tags = &set->sched_shared_breserved_tags; > + } > + } else { > + sbitmap_queue_free(&set->shared_bitmap_tags); > + sbitmap_queue_free(&set->shared_breserved_tags); > + if (!blk_mq_init_shared_sbitmap(set)) > + return -ENOMEM; /* fixup error handling */ No, we can't re-allocate driver tags here which are shared by all LUNs. And you should see that 'can_grow' is set as false for driver tags in blk_mq_update_nr_requests(), which can only touch per-request-queue data, not tagset wide data. Thanks, Ming
