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Commit 75c10e73 authored by Hannes Reinecke's avatar Hannes Reinecke Committed by Christoph Hellwig
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nvme-multipath: round-robin I/O policy 



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: default avatarHannes Reinecke <hare@suse.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent 49b1f22b

drivers/nvme/host/core.c

+6 −0
Original line number Diff line number Diff line
@@ -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;

drivers/nvme/host/multipath.c

+85 −1
Original line number Diff line number Diff line
@@ -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;



		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)

{

drivers/nvme/host/nvme.h

+9 −0
Original line number Diff line number Diff line
@@ -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)