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Tue, 21 May 2024 08:48:17 GMT Received: from smtpav05.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 0CB4B5805D; Tue, 21 May 2024 08:48:15 +0000 (GMT) Received: from smtpav05.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 41D0158053; Tue, 21 May 2024 08:48:11 +0000 (GMT) Received: from [9.171.37.250] (unknown [9.171.37.250]) by smtpav05.wdc07v.mail.ibm.com (Postfix) with ESMTP; Tue, 21 May 2024 08:48:10 +0000 (GMT) Message-ID: <945416af-3f8b-40b5-9681-49973beb2cb2@linux.ibm.com> Date: Tue, 21 May 2024 14:18:09 +0530 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/1] nvme: multipath: Implemented new iopolicy "queue-depth" To: John Meneghini , kbusch@kernel.org, hch@lst.de, sagi@grimberg.me, emilne@redhat.com Cc: linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, jrani@purestorage.com, randyj@purestorage.com, hare@kernel.org References: <20240520202045.427110-1-jmeneghi@redhat.com> <20240520202045.427110-2-jmeneghi@redhat.com> Content-Language: en-US From: Nilay Shroff In-Reply-To: <20240520202045.427110-2-jmeneghi@redhat.com> Content-Type: text/plain; charset=UTF-8 X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: 3l9zGOflHi9wVURUG_KoanMRZ1AsS-er X-Proofpoint-GUID: W_P4WROK6Mh8DK3lR-bMsNmLCgglWOf2 Content-Transfer-Encoding: 7bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.650,FMLib:17.12.28.16 definitions=2024-05-21_05,2024-05-21_01,2024-05-17_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 malwarescore=0 adultscore=0 phishscore=0 mlxscore=0 bulkscore=0 mlxlogscore=999 lowpriorityscore=0 suspectscore=0 clxscore=1011 spamscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2405010000 definitions=main-2405210065 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240521_014836_728871_74CB7128 X-CRM114-Status: GOOD ( 42.95 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On 5/21/24 01:50, John Meneghini wrote: > From: "Ewan D. Milne" > > The round-robin path selector is inefficient in cases where there is a > difference in latency between multiple active optimized paths. In the > presence of one or more high latency paths the round-robin selector > continues to the high latency path equally. This results in a bias > towards the highest latency path and can cause is significant decrease > in overall performance as IOs pile on the lowest latency path. This > problem is particularly accute with NVMe-oF controllers. > > The queue-depth policy instead sends I/O requests down the path with the > least amount of requests in its request queue. Paths with lower latency > will clear requests more quickly and have less requests in their queues > compared to higher latency paths. The goal of this path selector is to > make more use of lower latency paths, which will bring down overall IO > latency. > > Signed-off-by: Ewan D. Milne > [tsong: patch developed by Thomas Song @ Pure Storage, fixed whitespace > and compilation warnings, updated MODULE_PARM description, and > fixed potential issue with ->current_path[] being used] > Signed-off-by: Thomas Song > [jmeneghi: vairious changes and improvements, addressed review comments] > Signed-off-by: John Meneghini > Link: https://lore.kernel.org/linux-nvme/20240509202929.831680-1-jmeneghi@redhat.com/ > Tested-by: Marco Patalano > Reviewed-by: Randy Jennings > Tested-by: Jyoti Rani > --- > drivers/nvme/host/core.c | 2 +- > drivers/nvme/host/multipath.c | 86 +++++++++++++++++++++++++++++++++-- > drivers/nvme/host/nvme.h | 9 ++++ > 3 files changed, 92 insertions(+), 5 deletions(-) > > diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c > index a066429b790d..1dd7c52293ff 100644 > --- a/drivers/nvme/host/core.c > +++ b/drivers/nvme/host/core.c > @@ -110,7 +110,7 @@ struct workqueue_struct *nvme_delete_wq; > EXPORT_SYMBOL_GPL(nvme_delete_wq); > > static LIST_HEAD(nvme_subsystems); > -static DEFINE_MUTEX(nvme_subsystems_lock); > +DEFINE_MUTEX(nvme_subsystems_lock); > > static DEFINE_IDA(nvme_instance_ida); > static dev_t nvme_ctrl_base_chr_devt; > diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c > index 5397fb428b24..0e2b6e720e95 100644 > --- a/drivers/nvme/host/multipath.c > +++ b/drivers/nvme/host/multipath.c > @@ -17,6 +17,7 @@ MODULE_PARM_DESC(multipath, > static const char *nvme_iopolicy_names[] = { > [NVME_IOPOLICY_NUMA] = "numa", > [NVME_IOPOLICY_RR] = "round-robin", > + [NVME_IOPOLICY_QD] = "queue-depth", > }; > > static int iopolicy = NVME_IOPOLICY_NUMA; > @@ -29,6 +30,8 @@ static int nvme_set_iopolicy(const char *val, const struct kernel_param *kp) > iopolicy = NVME_IOPOLICY_NUMA; > else if (!strncmp(val, "round-robin", 11)) > iopolicy = NVME_IOPOLICY_RR; > + else if (!strncmp(val, "queue-depth", 11)) > + iopolicy = NVME_IOPOLICY_QD; > else > return -EINVAL; > > @@ -43,7 +46,7 @@ static int nvme_get_iopolicy(char *buf, const struct kernel_param *kp) > module_param_call(iopolicy, nvme_set_iopolicy, nvme_get_iopolicy, > &iopolicy, 0644); > MODULE_PARM_DESC(iopolicy, > - "Default multipath I/O policy; 'numa' (default) or 'round-robin'"); > + "Default multipath I/O policy; 'numa' (default) , 'round-robin' or 'queue-depth'"); > > void nvme_mpath_default_iopolicy(struct nvme_subsystem *subsys) > { > @@ -127,6 +130,11 @@ void nvme_mpath_start_request(struct request *rq) > struct nvme_ns *ns = rq->q->queuedata; > struct gendisk *disk = ns->head->disk; > > + if (READ_ONCE(ns->head->subsys->iopolicy) == NVME_IOPOLICY_QD) { > + atomic_inc(&ns->ctrl->nr_active); > + nvme_req(rq)->flags |= NVME_MPATH_CNT_ACTIVE; > + } > + > if (!blk_queue_io_stat(disk->queue) || blk_rq_is_passthrough(rq)) > return; > > @@ -140,8 +148,12 @@ void nvme_mpath_end_request(struct request *rq) > { > struct nvme_ns *ns = rq->q->queuedata; > > + if ((nvme_req(rq)->flags & NVME_MPATH_CNT_ACTIVE)) > + atomic_dec_if_positive(&ns->ctrl->nr_active); > + > if (!(nvme_req(rq)->flags & NVME_MPATH_IO_STATS)) > return; > + > bdev_end_io_acct(ns->head->disk->part0, req_op(rq), > blk_rq_bytes(rq) >> SECTOR_SHIFT, > nvme_req(rq)->start_time); > @@ -330,6 +342,40 @@ static struct nvme_ns *nvme_round_robin_path(struct nvme_ns_head *head, > return found; > } > I think you may also want to reset nr_active counter if in case, in-flight nvme request is cancelled. If the request is cancelled then nvme_mpath_end_request() wouldn't be invoked. So you may want to reset nr_active counter from nvme_cancel_request() as below: diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c index bf7615cb36ee..4fea7883ce8e 100644 --- a/drivers/nvme/host/core.c +++ b/drivers/nvme/host/core.c @@ -497,8 +497,9 @@ EXPORT_SYMBOL_GPL(nvme_host_path_error); bool nvme_cancel_request(struct request *req, void *data) { - dev_dbg_ratelimited(((struct nvme_ctrl *) data)->device, - "Cancelling I/O %d", req->tag); + struct nvme_ctrl *ctrl = (struct nvme_ctrl *)data; + + dev_dbg_ratelimited(ctrl->device, "Cancelling I/O %d", req->tag); /* don't abort one completed or idle request */ if (blk_mq_rq_state(req) != MQ_RQ_IN_FLIGHT) @@ -506,6 +507,8 @@ bool nvme_cancel_request(struct request *req, void *data) nvme_req(req)->status = NVME_SC_HOST_ABORTED_CMD; nvme_req(req)->flags |= NVME_REQ_CANCELLED; + if ((nvme_req(rq)->flags & NVME_MPATH_CNT_ACTIVE)) + atomic_dec(&ctrl->nr_active); blk_mq_complete_request(req); return true; } Please note that I am using atomic_dec() instead of atomic_dec_if_positive() above for the same reason as Keith mentioned in his earlier mail. > +static struct nvme_ns *nvme_queue_depth_path(struct nvme_ns_head *head) > +{ > + struct nvme_ns *best_opt = NULL, *best_nonopt = NULL, *ns; > + unsigned int min_depth_opt = UINT_MAX, min_depth_nonopt = UINT_MAX; > + unsigned int depth; > + > + list_for_each_entry_rcu(ns, &head->list, siblings) { > + if (nvme_path_is_disabled(ns)) > + continue; > + > + depth = atomic_read(&ns->ctrl->nr_active); > + > + switch (ns->ana_state) { > + case NVME_ANA_OPTIMIZED: > + if (depth < min_depth_opt) { > + min_depth_opt = depth; > + best_opt = ns; > + } > + break; > + > + case NVME_ANA_NONOPTIMIZED: > + if (depth < min_depth_nonopt) { > + min_depth_nonopt = depth; > + best_nonopt = ns; > + } > + break; > + default: > + break; > + } > + } > + > + return best_opt ? best_opt : best_nonopt; > +} > + > static inline bool nvme_path_is_optimized(struct nvme_ns *ns) > { > return nvme_ctrl_state(ns->ctrl) == NVME_CTRL_LIVE && > @@ -338,15 +384,27 @@ static inline bool nvme_path_is_optimized(struct nvme_ns *ns) > > inline struct nvme_ns *nvme_find_path(struct nvme_ns_head *head) > { > - int node = numa_node_id(); > + int iopolicy = READ_ONCE(head->subsys->iopolicy); > + int node; > struct nvme_ns *ns; > > + /* > + * queue-depth iopolicy does not need to reference ->current_path > + * but round-robin needs the last path used to advance to the > + * next one, and numa will continue to use the last path unless > + * it is or has become not optimized > + */ > + if (iopolicy == NVME_IOPOLICY_QD) > + return nvme_queue_depth_path(head); > + > + node = numa_node_id(); > ns = srcu_dereference(head->current_path[node], &head->srcu); > if (unlikely(!ns)) > return __nvme_find_path(head, node); > > - if (READ_ONCE(head->subsys->iopolicy) == NVME_IOPOLICY_RR) > + if (iopolicy == NVME_IOPOLICY_RR) > return nvme_round_robin_path(head, node, ns); > + > if (unlikely(!nvme_path_is_optimized(ns))) > return __nvme_find_path(head, node); > return ns; > @@ -798,6 +856,25 @@ static ssize_t nvme_subsys_iopolicy_show(struct device *dev, > nvme_iopolicy_names[READ_ONCE(subsys->iopolicy)]); > } > > +void nvme_subsys_iopolicy_update(struct nvme_subsystem *subsys, int iopolicy) > +{ > + struct nvme_ctrl *ctrl; > + int old_iopolicy = READ_ONCE(subsys->iopolicy); > + > + WRITE_ONCE(subsys->iopolicy, iopolicy); > + > + mutex_lock(&nvme_subsystems_lock); > + list_for_each_entry(ctrl, &subsys->ctrls, subsys_entry) { > + atomic_set(&ctrl->nr_active, 0); > + nvme_mpath_clear_ctrl_paths(ctrl); > + } > + mutex_unlock(&nvme_subsystems_lock); > + > + pr_notice("%s: changed from %s to %s for subsysnqn %s\n", __func__, > + nvme_iopolicy_names[old_iopolicy], nvme_iopolicy_names[iopolicy], > + subsys->subnqn); > +} > + > static ssize_t nvme_subsys_iopolicy_store(struct device *dev, > struct device_attribute *attr, const char *buf, size_t count) > { > @@ -807,7 +884,7 @@ static ssize_t nvme_subsys_iopolicy_store(struct device *dev, > > for (i = 0; i < ARRAY_SIZE(nvme_iopolicy_names); i++) { > if (sysfs_streq(buf, nvme_iopolicy_names[i])) { > - WRITE_ONCE(subsys->iopolicy, i); > + nvme_subsys_iopolicy_update(subsys, i); > return count; > } > } > @@ -905,6 +982,7 @@ void nvme_mpath_init_ctrl(struct nvme_ctrl *ctrl) > mutex_init(&ctrl->ana_lock); > timer_setup(&ctrl->anatt_timer, nvme_anatt_timeout, 0); > INIT_WORK(&ctrl->ana_work, nvme_ana_work); > + atomic_set(&ctrl->nr_active, 0); > } > > int nvme_mpath_init_identify(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id) > diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h > index f243a5822c2b..f5557889b244 100644 > --- a/drivers/nvme/host/nvme.h > +++ b/drivers/nvme/host/nvme.h > @@ -50,6 +50,8 @@ extern struct workqueue_struct *nvme_wq; > extern struct workqueue_struct *nvme_reset_wq; > extern struct workqueue_struct *nvme_delete_wq; > > +extern struct mutex nvme_subsystems_lock; > + > /* > * List of workarounds for devices that required behavior not specified in > * the standard. > @@ -190,6 +192,7 @@ enum { > NVME_REQ_CANCELLED = (1 << 0), > NVME_REQ_USERCMD = (1 << 1), > NVME_MPATH_IO_STATS = (1 << 2), > + NVME_MPATH_CNT_ACTIVE = (1 << 3), > }; > > static inline struct nvme_request *nvme_req(struct request *req) > @@ -354,6 +357,7 @@ struct nvme_ctrl { > size_t ana_log_size; > struct timer_list anatt_timer; > struct work_struct ana_work; > + atomic_t nr_active; > #endif > > #ifdef CONFIG_NVME_HOST_AUTH > @@ -402,6 +406,7 @@ static inline enum nvme_ctrl_state nvme_ctrl_state(struct nvme_ctrl *ctrl) > enum nvme_iopolicy { > NVME_IOPOLICY_NUMA, > NVME_IOPOLICY_RR, > + NVME_IOPOLICY_QD, > }; > > struct nvme_subsystem { > @@ -935,6 +940,7 @@ void nvme_mpath_clear_ctrl_paths(struct nvme_ctrl *ctrl); > void nvme_mpath_shutdown_disk(struct nvme_ns_head *head); > void nvme_mpath_start_request(struct request *rq); > void nvme_mpath_end_request(struct request *rq); > +void nvme_subsys_iopolicy_update(struct nvme_subsystem *subsys, int iopolicy); > > static inline void nvme_trace_bio_complete(struct request *req) > { > @@ -1034,6 +1040,9 @@ static inline bool nvme_disk_is_ns_head(struct gendisk *disk) > { > return false; > } > +static inline void nvme_subsys_iopolicy_update(struct nvme_subsystem *subsys, int iopolicy) > +{ > +} > #endif /* CONFIG_NVME_MULTIPATH */ > > int nvme_ns_report_zones(struct nvme_ns *ns, sector_t sector, Thanks, --Nilay