On 5/10/24 05:43, John Meneghini wrote: > From: Hannes Reinecke <hare@xxxxxxxxxx> > > Add a latency-based I/O policy for multipathing. It uses the blk-nodelat > latency tracker to provide latencies for each node, and schedules > I/O on the path with the least latency for the submitting node. > > Signed-off-by: Hannes Reinecke <hare@xxxxxxxxxx> > > Make this compile when CONFIG_BLK_NODE_LATENCY is not set. > Advertise the 'latency' iopolicy in modinfo. > > Signed-off-by: John Meneghini <jmeneghi@xxxxxxxxxx> > --- > drivers/nvme/host/multipath.c | 63 ++++++++++++++++++++++++++++++----- > drivers/nvme/host/nvme.h | 1 + > 2 files changed, 55 insertions(+), 9 deletions(-) > > diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c > index d916a5ddf5d4..e9330bb1990b 100644 > --- a/drivers/nvme/host/multipath.c > +++ b/drivers/nvme/host/multipath.c > @@ -18,6 +18,7 @@ static const char *nvme_iopolicy_names[] = { > [NVME_IOPOLICY_NUMA] = "numa", > [NVME_IOPOLICY_RR] = "round-robin", > [NVME_IOPOLICY_QD] = "queue-depth", > + [NVME_IOPOLICY_LAT] = "latency", > }; > > static int iopolicy = NVME_IOPOLICY_NUMA; > @@ -32,6 +33,10 @@ static int nvme_set_iopolicy(const char *val, const struct kernel_param *kp) > iopolicy = NVME_IOPOLICY_RR; > else if (!strncmp(val, "queue-depth", 11)) > iopolicy = NVME_IOPOLICY_QD; > +#ifdef CONFIG_BLK_NODE_LATENCY > + else if (!strncmp(val, "latency", 7)) > + iopolicy = NVME_IOPOLICY_LAT; > +#endif > else > return -EINVAL; > > @@ -43,10 +48,36 @@ static int nvme_get_iopolicy(char *buf, const struct kernel_param *kp) > return sprintf(buf, "%s\n", nvme_iopolicy_names[iopolicy]); > } > > +static int nvme_activate_iopolicy(struct nvme_subsystem *subsys, int iopolicy) > +{ > + struct nvme_ns_head *h; > + struct nvme_ns *ns; > + bool enable = iopolicy == NVME_IOPOLICY_LAT; > + int ret = 0; > + > + mutex_lock(&subsys->lock); > + list_for_each_entry(h, &subsys->nsheads, entry) { > + list_for_each_entry_rcu(ns, &h->list, siblings) { > + if (enable) { > + ret = blk_nlat_enable(ns->disk); > + if (ret) > + break; > + } else > + blk_nlat_disable(ns->disk); Missing curly brackets for the else. > + } > + } > + mutex_unlock(&subsys->lock); > + return ret; > +} > + > module_param_call(iopolicy, nvme_set_iopolicy, nvme_get_iopolicy, > &iopolicy, 0644); > MODULE_PARM_DESC(iopolicy, > +#if defined(CONFIG_BLK_NODE_LATENCY) What is so special about the latency policy that it needs to be conditionally defined ? I missed that point. Why not drop CONFIG_BLK_NODE_LATENCY ? > + "Default multipath I/O policy; 'numa' (default) , 'round-robin', 'queue-depth' or 'latency'"); > +#else > "Default multipath I/O policy; 'numa' (default) , 'round-robin' or 'queue-depth'"); > +#endif > > void nvme_mpath_default_iopolicy(struct nvme_subsystem *subsys) > { > @@ -250,14 +281,16 @@ static struct nvme_ns *__nvme_find_path(struct nvme_ns_head *head, int node) > { > int found_distance = INT_MAX, fallback_distance = INT_MAX, distance; > struct nvme_ns *found = NULL, *fallback = NULL, *ns; > + int iopolicy = READ_ONCE(head->subsys->iopolicy); > > list_for_each_entry_rcu(ns, &head->list, siblings) { > if (nvme_path_is_disabled(ns)) > continue; > > - if (ns->ctrl->numa_node != NUMA_NO_NODE && > - READ_ONCE(head->subsys->iopolicy) == NVME_IOPOLICY_NUMA) > + if (iopolicy == NVME_IOPOLICY_NUMA) > distance = node_distance(node, ns->ctrl->numa_node); > + else if (iopolicy == NVME_IOPOLICY_LAT) > + distance = blk_nlat_latency(ns->disk, node); > else > distance = LOCAL_DISTANCE; > > @@ -381,8 +414,8 @@ static inline bool nvme_path_is_optimized(struct nvme_ns *ns) > > inline struct nvme_ns *nvme_find_path(struct nvme_ns_head *head) > { > - int iopolicy = READ_ONCE(head->subsys->iopolicy); > int node; > + int iopolicy = READ_ONCE(head->subsys->iopolicy); No need to move this line. > struct nvme_ns *ns; > > /* > @@ -401,8 +434,8 @@ inline struct nvme_ns *nvme_find_path(struct nvme_ns_head *head) > > if (iopolicy == NVME_IOPOLICY_RR) > return nvme_round_robin_path(head, node, ns); > - > - if (unlikely(!nvme_path_is_optimized(ns))) > + if (iopolicy == NVME_IOPOLICY_LAT || > + unlikely(!nvme_path_is_optimized(ns))) > return __nvme_find_path(head, node); > return ns; > } > @@ -872,15 +905,18 @@ static ssize_t nvme_subsys_iopolicy_store(struct device *dev, > { > struct nvme_subsystem *subsys = > container_of(dev, struct nvme_subsystem, dev); > - int i; > + int i, ret; > > for (i = 0; i < ARRAY_SIZE(nvme_iopolicy_names); i++) { > if (sysfs_streq(buf, nvme_iopolicy_names[i])) { > - nvme_subsys_iopolicy_update(subsys, i); > - return count; > + ret = nvme_activate_iopolicy(subsys, i); > + if (!ret) { > + nvme_subsys_iopolicy_update(subsys, i); > + return count; > + } > + return ret; It would be nicer to have this as: if (ret) break nvme_subsys_iopolicy_update(subsys, i); return count; > } > } > - whiteline change. > return -EINVAL; And "return ret;" here with ret initialized to -EINVAL when declared. > } > SUBSYS_ATTR_RW(iopolicy, S_IRUGO | S_IWUSR, > @@ -916,6 +952,15 @@ static int nvme_lookup_ana_group_desc(struct nvme_ctrl *ctrl, > > void nvme_mpath_add_disk(struct nvme_ns *ns, __le32 anagrpid) > { > + if (!blk_nlat_init(ns->disk) && > + READ_ONCE(ns->head->subsys->iopolicy) == NVME_IOPOLICY_LAT) { > + int ret = blk_nlat_enable(ns->disk); > + > + if (unlikely(ret)) > + pr_warn("%s: Failed to enable latency tracking, error %d\n", > + ns->disk->disk_name, ret); > + } > + > if (nvme_ctrl_use_ana(ns->ctrl)) { > struct nvme_ana_group_desc desc = { > .grpid = anagrpid, > diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h > index a557b4577c01..66bf003a6c48 100644 > --- a/drivers/nvme/host/nvme.h > +++ b/drivers/nvme/host/nvme.h > @@ -411,6 +411,7 @@ enum nvme_iopolicy { > NVME_IOPOLICY_NUMA, > NVME_IOPOLICY_RR, > NVME_IOPOLICY_QD, > + NVME_IOPOLICY_LAT, > }; > > struct nvme_subsystem { -- Damien Le Moal Western Digital Research