[PATCH v8 6/9] selftests: ublk: kublk: decouple ublk_queues from ublk server threads

Add support in kublk for decoupled ublk_queues and ublk server threads. kublk now has two modes of operation:

- (preexisting mode) threads and queues are paired 1:1, and each thread services all the I/Os of one queue - (new mode) thread and queue counts are independently configurable. threads service I/Os in a way that balances load across threads even if load is not balanced over queues.

The default is the preexisting mode. The new mode is activated by passing the --per_io_tasks flag.

Signed-off-by: Uday Shankar ushankar@purestorage.com Reviewed-by: Ming Lei ming.lei@redhat.com --- tools/testing/selftests/ublk/file_backed.c | 4 +- tools/testing/selftests/ublk/kublk.c | 105 ++++++++++++++++++++++++----- tools/testing/selftests/ublk/kublk.h | 5 ++ tools/testing/selftests/ublk/null.c | 6 +- tools/testing/selftests/ublk/stripe.c | 4 +- 5 files changed, 100 insertions(+), 24 deletions(-)

diff --git a/tools/testing/selftests/ublk/file_backed.c b/tools/testing/selftests/ublk/file_backed.c index 922a87108b9f7bae53098e74602c7b1f3e0246bc..cfa59b631693793465f0e6909a6fbe1a364f4523 100644 --- a/tools/testing/selftests/ublk/file_backed.c +++ b/tools/testing/selftests/ublk/file_backed.c @@ -54,7 +54,7 @@ static int loop_queue_tgt_rw_io(struct ublk_queue *q, const struct ublksrv_io_de

ublk_io_alloc_sqes(ublk_get_io(q, tag), sqe, 3);

- io_uring_prep_buf_register(sqe[0], 0, tag, q->q_id, tag); + io_uring_prep_buf_register(sqe[0], 0, tag, q->q_id, ublk_get_io(q, tag)->buf_index); sqe[0]->flags |= IOSQE_CQE_SKIP_SUCCESS | IOSQE_IO_HARDLINK; sqe[0]->user_data = build_user_data(tag, ublk_cmd_op_nr(sqe[0]->cmd_op), 0, q->q_id, 1); @@ -66,7 +66,7 @@ static int loop_queue_tgt_rw_io(struct ublk_queue *q, const struct ublksrv_io_de sqe[1]->flags |= IOSQE_FIXED_FILE | IOSQE_IO_HARDLINK; sqe[1]->user_data = build_user_data(tag, ublk_op, 0, q->q_id, 1);

- io_uring_prep_buf_unregister(sqe[2], 0, tag, q->q_id, tag); + io_uring_prep_buf_unregister(sqe[2], 0, tag, q->q_id, ublk_get_io(q, tag)->buf_index); sqe[2]->user_data = build_user_data(tag, ublk_cmd_op_nr(sqe[2]->cmd_op), 0, q->q_id, 1);

return 2; diff --git a/tools/testing/selftests/ublk/kublk.c b/tools/testing/selftests/ublk/kublk.c index 40431a8357a8f74d7d62e271e9090c8708c3ecc5..a98e14e4c245965d817b93843ff9a4011291223b 100644 --- a/tools/testing/selftests/ublk/kublk.c +++ b/tools/testing/selftests/ublk/kublk.c @@ -505,8 +505,11 @@ static int ublk_thread_init(struct ublk_thread *t) }

if (dev->dev_info.flags & (UBLK_F_SUPPORT_ZERO_COPY | UBLK_F_AUTO_BUF_REG)) { + unsigned nr_ios = dev->dev_info.queue_depth * dev->dev_info.nr_hw_queues; + unsigned max_nr_ios_per_thread = nr_ios / dev->nthreads; + max_nr_ios_per_thread += !!(nr_ios % dev->nthreads); ret = io_uring_register_buffers_sparse( - &t->ring, dev->dev_info.queue_depth); + &t->ring, max_nr_ios_per_thread); if (ret) { ublk_err("ublk dev %d thread %d register spare buffers failed %d", dev->dev_info.dev_id, t->idx, ret); @@ -578,7 +581,7 @@ static void ublk_set_auto_buf_reg(const struct ublk_queue *q, if (q->tgt_ops->buf_index) buf.index = q->tgt_ops->buf_index(q, tag); else - buf.index = tag; + buf.index = q->ios[tag].buf_index;

if (q->state & UBLKSRV_AUTO_BUF_REG_FALLBACK) buf.flags = UBLK_AUTO_BUF_REG_FALLBACK; @@ -660,18 +663,44 @@ int ublk_queue_io_cmd(struct ublk_io *io)

static void ublk_submit_fetch_commands(struct ublk_thread *t) { - /* - * Service exclusively the queue whose q_id matches our thread - * index. This may change in the future. - */ - struct ublk_queue *q = &t->dev->q[t->idx]; + struct ublk_queue *q; struct ublk_io *io; - int i = 0; + int i = 0, j = 0;

- for (i = 0; i < q->q_depth; i++) { - io = &q->ios[i]; - io->t = t; - ublk_queue_io_cmd(io); + if (t->dev->per_io_tasks) { + /* + * Lexicographically order all the (qid,tag) pairs, with + * qid taking priority (so (1,0) > (0,1)). Then make + * this thread the daemon for every Nth entry in this + * list (N is the number of threads), starting at this + * thread's index. This ensures that each queue is + * handled by as many ublk server threads as possible, + * so that load that is concentrated on one or a few + * queues can make use of all ublk server threads. + */ + const struct ublksrv_ctrl_dev_info *dinfo = &t->dev->dev_info; + int nr_ios = dinfo->nr_hw_queues * dinfo->queue_depth; + for (i = t->idx; i < nr_ios; i += t->dev->nthreads) { + int q_id = i / dinfo->queue_depth; + int tag = i % dinfo->queue_depth; + q = &t->dev->q[q_id]; + io = &q->ios[tag]; + io->t = t; + io->buf_index = j++; + ublk_queue_io_cmd(io); + } + } else { + /* + * Service exclusively the queue whose q_id matches our + * thread index. + */ + struct ublk_queue *q = &t->dev->q[t->idx]; + for (i = 0; i < q->q_depth; i++) { + io = &q->ios[i]; + io->t = t; + io->buf_index = i; + ublk_queue_io_cmd(io); + } } }

@@ -826,7 +855,8 @@ static void *ublk_io_handler_fn(void *data) return NULL; } /* IO perf is sensitive with queue pthread affinity on NUMA machine*/ - ublk_thread_set_sched_affinity(t, info->affinity); + if (info->affinity) + ublk_thread_set_sched_affinity(t, info->affinity); sem_post(info->ready);

ublk_dbg(UBLK_DBG_THREAD, "tid %d: ublk dev %d thread %u started\n", @@ -893,7 +923,7 @@ static int ublk_start_daemon(const struct dev_ctx *ctx, struct ublk_dev *dev)

ublk_dbg(UBLK_DBG_DEV, "%s enter\n", __func__);

- tinfo = calloc(sizeof(struct ublk_thread_info), dinfo->nr_hw_queues); + tinfo = calloc(sizeof(struct ublk_thread_info), dev->nthreads); if (!tinfo) return -ENOMEM;

@@ -919,17 +949,29 @@ static int ublk_start_daemon(const struct dev_ctx *ctx, struct ublk_dev *dev) dinfo->dev_id, i); goto fail; } + }

+ for (i = 0; i < dev->nthreads; i++) { tinfo[i].dev = dev; tinfo[i].idx = i; tinfo[i].ready = &ready; - tinfo[i].affinity = &affinity_buf[i]; + + /* + * If threads are not tied 1:1 to queues, setting thread + * affinity based on queue affinity makes little sense. + * However, thread CPU affinity has significant impact + * on performance, so to compare fairly, we'll still set + * thread CPU affinity based on queue affinity where + * possible. + */ + if (dev->nthreads == dinfo->nr_hw_queues) + tinfo[i].affinity = &affinity_buf[i]; pthread_create(&dev->threads[i].thread, NULL, ublk_io_handler_fn, &tinfo[i]); }

- for (i = 0; i < dinfo->nr_hw_queues; i++) + for (i = 0; i < dev->nthreads; i++) sem_wait(&ready); free(tinfo); free(affinity_buf); @@ -953,7 +995,7 @@ static int ublk_start_daemon(const struct dev_ctx *ctx, struct ublk_dev *dev) ublk_send_dev_event(ctx, dev, dev->dev_info.dev_id);

/* wait until we are terminated */ - for (i = 0; i < dinfo->nr_hw_queues; i++) + for (i = 0; i < dev->nthreads; i++) pthread_join(dev->threads[i].thread, &thread_ret); fail: for (i = 0; i < dinfo->nr_hw_queues; i++) @@ -1063,6 +1105,7 @@ static int ublk_stop_io_daemon(const struct ublk_dev *dev)

static int __cmd_dev_add(const struct dev_ctx *ctx) { + unsigned nthreads = ctx->nthreads; unsigned nr_queues = ctx->nr_hw_queues; const char *tgt_type = ctx->tgt_type; unsigned depth = ctx->queue_depth; @@ -1086,6 +1129,23 @@ static int __cmd_dev_add(const struct dev_ctx *ctx) return -EINVAL; }

+ /* default to 1:1 threads:queues if nthreads is unspecified */ + if (!nthreads) + nthreads = nr_queues; + + if (nthreads > UBLK_MAX_THREADS) { + ublk_err("%s: %u is too many threads (max %u)\n", + __func__, nthreads, UBLK_MAX_THREADS); + return -EINVAL; + } + + if (nthreads != nr_queues && !ctx->per_io_tasks) { + ublk_err("%s: threads %u must be same as queues %u if " + "not using per_io_tasks\n", + __func__, nthreads, nr_queues); + return -EINVAL; + } + dev = ublk_ctrl_init(); if (!dev) { ublk_err("%s: can't alloc dev id %d, type %s\n", @@ -1109,6 +1169,8 @@ static int __cmd_dev_add(const struct dev_ctx *ctx) if ((features & UBLK_F_QUIESCE) && (info->flags & UBLK_F_USER_RECOVERY)) info->flags |= UBLK_F_QUIESCE; + dev->nthreads = nthreads; + dev->per_io_tasks = ctx->per_io_tasks; dev->tgt.ops = ops; dev->tgt.sq_depth = depth; dev->tgt.cq_depth = depth; @@ -1307,6 +1369,7 @@ static int cmd_dev_get_features(void) [const_ilog2(UBLK_F_UPDATE_SIZE)] = "UPDATE_SIZE", [const_ilog2(UBLK_F_AUTO_BUF_REG)] = "AUTO_BUF_REG", [const_ilog2(UBLK_F_QUIESCE)] = "QUIESCE", + [const_ilog2(UBLK_F_PER_IO_DAEMON)] = "PER_IO_DAEMON", }; struct ublk_dev *dev; __u64 features = 0; @@ -1401,8 +1464,10 @@ static void __cmd_create_help(char *exe, bool recovery) exe, recovery ? "recover" : "add"); printf("\t[--foreground] [--quiet] [-z] [--auto_zc] [--auto_zc_fallback] [--debug_mask mask] [-r 0|1 ] [-g]\n"); printf("\t[-e 0|1 ] [-i 0|1]\n"); + printf("\t[--nthreads threads] [--per_io_tasks]\n"); printf("\t[target options] [backfile1] [backfile2] ...\n"); printf("\tdefault: nr_queues=2(max 32), depth=128(max 1024), dev_id=-1(auto allocation)\n"); + printf("\tdefault: nthreads=nr_queues");

for (i = 0; i < sizeof(tgt_ops_list) / sizeof(tgt_ops_list[0]); i++) { const struct ublk_tgt_ops *ops = tgt_ops_list[i]; @@ -1459,6 +1524,8 @@ int main(int argc, char *argv[]) { "auto_zc", 0, NULL, 0 }, { "auto_zc_fallback", 0, NULL, 0 }, { "size", 1, NULL, 's'}, + { "nthreads", 1, NULL, 0 }, + { "per_io_tasks", 0, NULL, 0 }, { 0, 0, 0, 0 } }; const struct ublk_tgt_ops *ops = NULL; @@ -1534,6 +1601,10 @@ int main(int argc, char *argv[]) ctx.flags |= UBLK_F_AUTO_BUF_REG; if (!strcmp(longopts[option_idx].name, "auto_zc_fallback")) ctx.auto_zc_fallback = 1; + if (!strcmp(longopts[option_idx].name, "nthreads")) + ctx.nthreads = strtol(optarg, NULL, 10); + if (!strcmp(longopts[option_idx].name, "per_io_tasks")) + ctx.per_io_tasks = 1; break; case '?': /* diff --git a/tools/testing/selftests/ublk/kublk.h b/tools/testing/selftests/ublk/kublk.h index 3a2ae095bee18633acd5a9c923cfab2d14fe3bff..6be601536b3d2c095654da5fba0cf13a51142052 100644 --- a/tools/testing/selftests/ublk/kublk.h +++ b/tools/testing/selftests/ublk/kublk.h @@ -80,6 +80,7 @@ struct dev_ctx { char tgt_type[16]; unsigned long flags; unsigned nr_hw_queues; + unsigned short nthreads; unsigned queue_depth; int dev_id; int nr_files; @@ -89,6 +90,7 @@ struct dev_ctx { unsigned int fg:1; unsigned int recovery:1; unsigned int auto_zc_fallback:1; + unsigned int per_io_tasks:1;

int _evtfd; int _shmid; @@ -131,6 +133,7 @@ struct ublk_io {

int result;

+ unsigned short buf_index; unsigned short tgt_ios; void *private_data; struct ublk_thread *t; @@ -203,6 +206,8 @@ struct ublk_dev { struct ublksrv_ctrl_dev_info dev_info; struct ublk_queue q[UBLK_MAX_QUEUES]; struct ublk_thread threads[UBLK_MAX_THREADS]; + unsigned nthreads; + unsigned per_io_tasks;

int fds[MAX_BACK_FILES + 1]; /* fds[0] points to /dev/ublkcN */ int nr_fds; diff --git a/tools/testing/selftests/ublk/null.c b/tools/testing/selftests/ublk/null.c index 9acc7e0d271b5ae52d6d31587cc5bfb63b19778d..afe0b99d77eec74acae04952a9af5348252bc599 100644 --- a/tools/testing/selftests/ublk/null.c +++ b/tools/testing/selftests/ublk/null.c @@ -62,7 +62,7 @@ static int null_queue_zc_io(struct ublk_queue *q, int tag)

ublk_io_alloc_sqes(ublk_get_io(q, tag), sqe, 3);

- io_uring_prep_buf_register(sqe[0], 0, tag, q->q_id, tag); + io_uring_prep_buf_register(sqe[0], 0, tag, q->q_id, ublk_get_io(q, tag)->buf_index); sqe[0]->user_data = build_user_data(tag, ublk_cmd_op_nr(sqe[0]->cmd_op), 0, q->q_id, 1); sqe[0]->flags |= IOSQE_CQE_SKIP_SUCCESS | IOSQE_IO_HARDLINK; @@ -70,7 +70,7 @@ static int null_queue_zc_io(struct ublk_queue *q, int tag) __setup_nop_io(tag, iod, sqe[1], q->q_id); sqe[1]->flags |= IOSQE_IO_HARDLINK;

- io_uring_prep_buf_unregister(sqe[2], 0, tag, q->q_id, tag); + io_uring_prep_buf_unregister(sqe[2], 0, tag, q->q_id, ublk_get_io(q, tag)->buf_index); sqe[2]->user_data = build_user_data(tag, ublk_cmd_op_nr(sqe[2]->cmd_op), 0, q->q_id, 1);

// buf register is marked as IOSQE_CQE_SKIP_SUCCESS @@ -136,7 +136,7 @@ static unsigned short ublk_null_buf_index(const struct ublk_queue *q, int tag) { if (q->state & UBLKSRV_AUTO_BUF_REG_FALLBACK) return (unsigned short)-1; - return tag; + return q->ios[tag].buf_index; }

const struct ublk_tgt_ops null_tgt_ops = { diff --git a/tools/testing/selftests/ublk/stripe.c b/tools/testing/selftests/ublk/stripe.c index 97079c3121ef8d4edc71891a289dd40658ce3f2a..37d50bbf5f5e86a520efedc9228510f8e1273625 100644 --- a/tools/testing/selftests/ublk/stripe.c +++ b/tools/testing/selftests/ublk/stripe.c @@ -141,7 +141,7 @@ static int stripe_queue_tgt_rw_io(struct ublk_queue *q, const struct ublksrv_io_ ublk_io_alloc_sqes(ublk_get_io(q, tag), sqe, s->nr + extra);

if (zc) { - io_uring_prep_buf_register(sqe[0], 0, tag, q->q_id, tag); + io_uring_prep_buf_register(sqe[0], 0, tag, q->q_id, io->buf_index); sqe[0]->flags |= IOSQE_CQE_SKIP_SUCCESS | IOSQE_IO_HARDLINK; sqe[0]->user_data = build_user_data(tag, ublk_cmd_op_nr(sqe[0]->cmd_op), 0, q->q_id, 1); @@ -167,7 +167,7 @@ static int stripe_queue_tgt_rw_io(struct ublk_queue *q, const struct ublksrv_io_ if (zc) { struct io_uring_sqe *unreg = sqe[s->nr + 1];

- io_uring_prep_buf_unregister(unreg, 0, tag, q->q_id, tag); + io_uring_prep_buf_unregister(unreg, 0, tag, q->q_id, io->buf_index); unreg->user_data = build_user_data( tag, ublk_cmd_op_nr(unreg->cmd_op), 0, q->q_id, 1); }