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nvme-multipath: round-robin I/O policy

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Implement a simple round-robin I/O policy for multipathing.  Path
selection is done in two rounds, first iterating across all optimized
paths, and if that doesn't return any valid paths, iterate over all
optimized and non-optimized paths.  If no paths are found, use the
existing algorithm.  Also add a sysfs attribute 'iopolicy' to switch
between the current NUMA-aware I/O policy and the 'round-robin' I/O
policy.

Signed-off-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Hannes Reinecke 2019-02-18 11:43:26 +01:00 committed by Christoph Hellwig
parent 49b1f22b56
commit 75c10e7327
3 changed files with 100 additions and 1 deletions
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6
drivers/nvme/host/core.c
View File

@ -2328,6 +2328,9 @@ static struct attribute *nvme_subsys_attrs[] = {
&subsys_attr_serial.attr,
&subsys_attr_firmware_rev.attr,
&subsys_attr_subsysnqn.attr,
#ifdef CONFIG_NVME_MULTIPATH
&subsys_attr_iopolicy.attr,
#endif
NULL,
};
@ -2380,6 +2383,9 @@ static int nvme_init_subsystem(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id)
memcpy(subsys->firmware_rev, id->fr, sizeof(subsys->firmware_rev));
subsys->vendor_id = le16_to_cpu(id->vid);
subsys->cmic = id->cmic;
#ifdef CONFIG_NVME_MULTIPATH
subsys->iopolicy = NVME_IOPOLICY_NUMA;
#endif
subsys->dev.class = nvme_subsys_class;
subsys->dev.release = nvme_release_subsystem;

86
drivers/nvme/host/multipath.c
View File

@ -141,7 +141,10 @@ static struct nvme_ns *__nvme_find_path(struct nvme_ns_head *head, int node)
test_bit(NVME_NS_ANA_PENDING, &ns->flags))
continue;
distance = node_distance(node, ns->ctrl->numa_node);
if (READ_ONCE(head->subsys->iopolicy) == NVME_IOPOLICY_NUMA)
distance = node_distance(node, ns->ctrl->numa_node);
else
distance = LOCAL_DISTANCE;
switch (ns->ana_state) {
case NVME_ANA_OPTIMIZED:
@ -168,6 +171,47 @@ static struct nvme_ns *__nvme_find_path(struct nvme_ns_head *head, int node)
return found;
}
static struct nvme_ns *nvme_next_ns(struct nvme_ns_head *head,
struct nvme_ns *ns)
{
ns = list_next_or_null_rcu(&head->list, &ns->siblings, struct nvme_ns,
siblings);
if (ns)
return ns;
return list_first_or_null_rcu(&head->list, struct nvme_ns, siblings);
}
static struct nvme_ns *nvme_round_robin_path(struct nvme_ns_head *head,
int node, struct nvme_ns *old)
{
struct nvme_ns *ns, *found, *fallback = NULL;
if (list_is_singular(&head->list))
return old;
for (ns = nvme_next_ns(head, old);
ns != old;
ns = nvme_next_ns(head, ns)) {
if (ns->ctrl->state != NVME_CTRL_LIVE ||
test_bit(NVME_NS_ANA_PENDING, &ns->flags))
continue;
if (ns->ana_state == NVME_ANA_OPTIMIZED) {
found = ns;
goto out;
}
if (ns->ana_state == NVME_ANA_NONOPTIMIZED)
fallback = ns;
}
if (!fallback)
return NULL;
found = fallback;
out:
rcu_assign_pointer(head->current_path[node], found);
return found;
}
static inline bool nvme_path_is_optimized(struct nvme_ns *ns)
{
return ns->ctrl->state == NVME_CTRL_LIVE &&
@ -180,6 +224,8 @@ inline struct nvme_ns *nvme_find_path(struct nvme_ns_head *head)
struct nvme_ns *ns;
ns = srcu_dereference(head->current_path[node], &head->srcu);
if (READ_ONCE(head->subsys->iopolicy) == NVME_IOPOLICY_RR && ns)
ns = nvme_round_robin_path(head, node, ns);
if (unlikely(!ns || !nvme_path_is_optimized(ns)))
ns = __nvme_find_path(head, node);
return ns;
@ -471,6 +517,44 @@ void nvme_mpath_stop(struct nvme_ctrl *ctrl)
cancel_work_sync(&ctrl->ana_work);
}
#define SUBSYS_ATTR_RW(_name, _mode, _show, _store) \
struct device_attribute subsys_attr_##_name = \
__ATTR(_name, _mode, _show, _store)
static const char *nvme_iopolicy_names[] = {
[NVME_IOPOLICY_NUMA] = "numa",
[NVME_IOPOLICY_RR] = "round-robin",
};
static ssize_t nvme_subsys_iopolicy_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct nvme_subsystem *subsys =
container_of(dev, struct nvme_subsystem, dev);
return sprintf(buf, "%s\n",
nvme_iopolicy_names[READ_ONCE(subsys->iopolicy)]);
}
static ssize_t nvme_subsys_iopolicy_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t count)
{
struct nvme_subsystem *subsys =
container_of(dev, struct nvme_subsystem, dev);
int i;
for (i = 0; i < ARRAY_SIZE(nvme_iopolicy_names); i++) {
if (sysfs_streq(buf, nvme_iopolicy_names[i])) {
WRITE_ONCE(subsys->iopolicy, i);
return count;
}
}
return -EINVAL;
}
SUBSYS_ATTR_RW(iopolicy, S_IRUGO | S_IWUSR,
nvme_subsys_iopolicy_show, nvme_subsys_iopolicy_store);
static ssize_t ana_grpid_show(struct device *dev, struct device_attribute *attr,
char *buf)
{

9
drivers/nvme/host/nvme.h
View File

@ -252,6 +252,11 @@ struct nvme_ctrl {
unsigned long discard_page_busy;
};
enum nvme_iopolicy {
NVME_IOPOLICY_NUMA,
NVME_IOPOLICY_RR,
};
struct nvme_subsystem {
int instance;
struct device dev;
@ -271,6 +276,9 @@ struct nvme_subsystem {
u8 cmic;
u16 vendor_id;
struct ida ns_ida;
#ifdef CONFIG_NVME_MULTIPATH
enum nvme_iopolicy iopolicy;
#endif
};
/*
@ -491,6 +499,7 @@ static inline void nvme_mpath_check_last_path(struct nvme_ns *ns)
extern struct device_attribute dev_attr_ana_grpid;
extern struct device_attribute dev_attr_ana_state;
extern struct device_attribute subsys_attr_iopolicy;
#else
static inline bool nvme_ctrl_use_ana(struct nvme_ctrl *ctrl)