Libfabric Programmer's Manual

fi_av(3) Libfabric Programmer's Manual

NAME

fi_av - Address vector operations

fi_av_open / fi_close
Open or close an address vector
fi_av_bind
Associate an address vector with an event queue.
fi_av_insert / fi_av_insertsvc / fi_av_remove
Insert/remove an address into/from the address vector.
fi_av_lookup
Retrieve an address stored in the address vector.
fi_av_straddr
Convert an address into a printable string.

SYNOPSIS

#include <rdma/fi_domain.h>

int fi_av_open(struct fid_domain *domain, struct fi_av_attr *attr,
    struct fid_av **av, void *context);

int fi_close(struct fid *av);

int fi_av_bind(struct fid_av *av, struct fid *eq, uint64_t flags);

int fi_av_insert(struct fid_av *av, void *addr, size_t count,
    fi_addr_t *fi_addr, uint64_t flags, void *context);

int fi_av_insertsvc(struct fid_av *av, const char *node,
    const char *service, fi_addr_t *fi_addr, uint64_t flags,
    void *context);

int fi_av_insertsym(struct fid_av *av, const char *node,
    size_t nodecnt, const char *service, size_t svccnt,
    fi_addr_t *fi_addr, uint64_t flags, void *context);

int fi_av_remove(struct fid_av *av, fi_addr_t *fi_addr, size_t count,
    uint64_t flags);

int fi_av_lookup(struct fid_av *av, fi_addr_t fi_addr,
    void *addr, size_t *addrlen);

fi_addr_t fi_rx_addr(fi_addr_t fi_addr, int rx_index,
	  int rx_ctx_bits);

const char * fi_av_straddr(struct fid_av *av, const void *addr,
      char *buf, size_t *len);

ARGUMENTS

domain
Resource domain
av
Address vector
eq
Event queue
attr
Address vector attributes
context
User specified context associated with the address vector or insert operation.
addr
Buffer containing one or more addresses to insert into address vector.
addrlen
On input, specifies size of addr buffer. On output, stores number of bytes written to addr buffer.
fi_addr
For insert, a reference to an array where returned fabric addresses will be written. For remove, one or more fabric addresses to remove.
count
Number of addresses to insert/remove from an AV.
flags
Additional flags to apply to the operation.

DESCRIPTION

Address vectors are used to map higher level addresses, which may be more natural for an application to use, into fabric specific addresses. The mapping of addresses is fabric and provider specific, but may involve lengthy address resolution and fabric management protocols. AV operations are synchronous by default, but may be set to operate asynchronously by specifying the FI_EVENT flag to fi_av_open. When requesting asynchronous operation, the application must first bind an event queue to the AV before inserting addresses.

fi_av_open

fi_av_open allocates or opens an address vector. The properties and behavior of the address vector are defined by struct fi_av_attr.

struct fi_av_attr {
	enum fi_av_type  type;        /* type of AV */
	int              rx_ctx_bits; /* address bits to identify rx ctx */
	size_t           count;       /* # entries for AV */
	size_t           ep_per_node; /* # endpoints per fabric address */
	const char       *name;       /* system name of AV */
	void             *map_addr;   /* base mmap address */
	uint64_t         flags;       /* operation flags */
};
type
An AV type corresponds to a conceptual implementation of an address vector. The type specifies how an application views data stored in the AV, including how it may be accessed. Valid values are:
  • FI_AV_MAP
    Addresses which are inserted into an AV are mapped to a native fabric address for use by the application. The use of FI_AV_MAP requires that an application store the returned fi_addr_t value that is associated with each inserted address. The advantage of using FI_AV_MAP is that the returned fi_addr_t value may contain encoded address data, which is immediately available when processing data transfer requests. This can eliminate or reduce the number of memory lookups needed when initiating a transfer. The disadvantage of FI_AV_MAP is the increase in memory usage needed to store the returned addresses. Addresses are stored in the AV using a provider specific mechanism, including, but not limited to a tree, hash table, or maintained on the heap.
  • FI_AV_TABLE
    Addresses which are inserted into an AV of type FI_AV_TABLE are accessible using a simple index. Conceptually, the AV may be treated as an array of addresses, though the provider may implement the AV using a variety of mechanisms. When FI_AV_TABLE is used, the returned fi_addr_t is an index, with the index for an inserted address the same as its insertion order into the table. The index of the first address inserted into an FI_AV_TABLE will be 0, and successive insertions will be given sequential indices. Sequential indices will be assigned across insertion calls on the same AV.
  • FI_AV_UNSPEC
    Provider will choose its preferred AV type. The AV type used will be returned through the type field in fi_av_attr.
Receive Context Bits (rx_ctx_bits)
The receive context bits field is only for use with scalable endpoints. It indicates the number of bits reserved in a returned fi_addr_t, which will be used to identify a specific target receive context. See fi_rx_addr() and fi_endpoint(3) for additional details on receive contexts. The requested number of bits should be selected such that 2 ^ rx_ctx_bits >= rx_ctx_cnt for the endpoint.
count
Indicates the expected number of addresses that will be inserted into the AV. The provider uses this to optimize resource allocations.
ep_per_node
This field indicates the number of endpoints that will be associated with a specific fabric, or network, address. If the number of endpoints per node is unknown, this value should be set to 0. The provider uses this value to optimize resource allocations. For example, distributed, parallel applications may set this to the number of processes allocated per node, times the number of endpoints each process will open.
name
An optional system name associated with the address vector to create or open. Address vectors may be shared across multiple processes which access the same named domain on the same node. The name field allows the underlying provider to identify a shared AV.

If the name field is non-NULL and the AV is not opened for read-only access, a named AV will be created, if it does not already exist.

map_addr
The map_addr determines the base fi_addr_t address that a provider should use when sharing an AV of type FI_AV_MAP between processes. Processes that provide the same value for map_addr to a shared AV may use the same fi_addr_t values returned from an fi_av_insert call.

The map_addr may be used by the provider to mmap memory allocated for a shared AV between processes; however, the provider is not required to use the map_addr in this fashion. The only requirement is that an fi_addr_t returned as part of an fi_av_insert call on one process is usable on another process which opens an AV of the same name at the same map_addr value. The relationship between the map_addr and any returned fi_addr_t is not defined.

If name is non-NULL and map_addr is 0, then the map_addr used by the provider will be returned through the attribute structure. The map_addr field is ignored if name is NULL.

flags
The following flags may be used when opening an AV.
  • FI_EVENT
    When the flag FI_EVENT is specified, all insert operations on this AV will occur asynchronously. There will be one EQ error entry generated for each failed address insertion, followed by one non-error event indicating that the insertion operation has completed. There will always be one non-error completion event for each insert operation, even if all addresses fail. The context field in all completions will be the context specified to the insert call, and the data field in the final completion entry will report the number of addresses successfully inserted. If an error occurs during the asynchronous insertion, an error completion entry is returned (see fi_eq(3) for a discussion of the fi_eq_err_entry error completion struct). The context field of the error completion will be the context that was specified in the insert call; the data field will contain the index of the failed address. There will be one error completion returned for each address that fails to insert into the AV.

    If an AV is opened with FI_EVENT, any insertions attempted before an EQ is bound to the AV will fail with -FI_ENOEQ.

    Error completions for failed insertions will contain the index of the failed address in the index field of the error completion entry.

    Note that the order of delivery of insert completions may not match the order in which the calls to fi_av_insert were made. The only guarantee is that all error completions for a given call to fi_av_insert will precede the single associated non-error completion.

  • FI_READ
    Opens an AV for read-only access. An AV opened for read-only access must be named (name attribute specified), and the AV must exist.
  • FI_SYMMETRIC
    Indicates that each node will be associated with the same number of endpoints, the same transport addresses will be allocated on each node, and the transport addresses will be sequential. This feature targets distributed applications on large fabrics and allows for highly-optimized storage of remote endpoint addressing.

fi_close

The fi_close call is used to release all resources associated with an address vector. Note that any events queued on an event queue referencing the AV are left untouched. It is recommended that callers retrieve all events associated with the AV before closing it.

When closing the address vector, there must be no opened endpoints associated with the AV. If resources are still associated with the AV when attempting to close, the call will return -FI_EBUSY.

fi_av_bind

Associates an event queue with the AV. If an AV has been opened with FI_EVENT, then an event queue must be bound to the AV before any insertion calls are attempted. Any calls to insert addresses before an event queue has been bound will fail with -FI_ENOEQ.

fi_av_insert

The fi_av_insert call inserts zero or more addresses into an AV. The number of addresses is specified through the count parameter. The addr parameter references an array of addresses to insert into the AV. Addresses inserted into an address vector must be in the same format as specified in the addr_format field of the fi_info struct provided when opening the corresponding domain.

For AV’s of type FI_AV_MAP, once inserted addresses have been mapped, the mapped values are written into the buffer referenced by fi_addr. The fi_addr buffer must remain valid until the AV insertion has completed and an event has been generated to an associated event queue. The value of the returned fi_addr should be considered opaque by the application for AVs of type FI_AV_MAP. The returned value may point to an internal structure or a provider specific encoding of low-level addressing data, for example. In the latter case, use of FI_AV_MAP may be able to avoid memory references during data transfer operations.

For AV’s of type FI_AV_TABLE, addresses are placed into the table in order. An address is inserted at the lowest index that corresponds to an unused table location, with indices starting at 0. That is, the first address inserted may be referenced at index 0, the second at index 1, and so forth. When addresses are inserted into an AV table, the assigned fi_addr values will be simple indices corresponding to the entry into the table where the address was inserted. Index values accumulate across successive insert calls in the order the calls are made, not necessarily in the order the insertions complete.

Because insertions occur at a pre-determined index, the fi_addr parameter may be NULL. If fi_addr is non-NULL, it must reference an array of fi_addr_t, and the buffer must remain valid until the insertion operation completes. Note that if fi_addr is NULL and synchronous operation is requested, individual insertion failures cannot be reported and the application must use other calls, such as fi_av_lookup to learn which specific addresses failed to insert. Since fi_av_remove is provider-specific, it is recommended that calls to fi_av_insert following a call to fi_av_remove always reference a valid buffer in the fi_addr parameter. Otherwise it may be difficult to determine what the next assigned index will be.

flags
The following flag may be passed to fi_av_insert
  • FI_MORE
    In order to allow optimized address insertion, the application may specify the FI_MORE flag to the insert call to give a hint to the provider that more insertion requests will follow, allowing the provider to aggregate insertion requests if desired. Providers are free to ignore FI_MORE.

fi_av_insertsvc

The fi_av_insertsvc call behaves similar to fi_av_insert, but allows the application to specify the node and service names, similar to the fi_getinfo inputs, rather than an encoded address. The node and service parameters are defined the same as fi_getinfo(3). Node should be a string that corresponds to a hostname or network address. The service string corresponds to a textual representation of a transport address.

fi_av_insertsym

fi_av_insertsym performs a symmetric insert that inserts a sequential range of nodes and/or service addresses into an AV. The svccnt parameter indicates the number of transport (endpoint) addresses to insert into the AV for each node address, with the service parameter specifying the starting transport address. Inserted transport addresses will be of the range {service, service + svccnt - 1}, inclusive. All service addresses for a node will be inserted before the next node is inserted.

The nodecnt parameter indicates the number of node (network) addresses to insert into the AV, with the node parameter specifying the starting node address. Inserted node addresses will be of the range {node, node + nodecnt - 1}, inclusive. If node is a non-numeric string, such as a hostname, it must contain a numeric suffix if nodecnt > 1.

As an example, if node = “10.1.1.1”, nodecnt = 2, service = “5000”, and svccnt = 2, the following addresses will be inserted into the AV in the order shown: 10.1.1.1:5000, 10.1.1.1:5001, 10.1.1.2:5000, 10.1.1.2:5001. If node were replaced by the hostname “host10”, the addresses would be: host10:5000, host10:5001, host11:5000, host11:5001.

The total number of inserted addresses will be nodecnt x svccnt.

fi_av_remove

fi_av_remove removes a set of addresses from an address vector. All resources associated with the indicated addresses are released. The removed address - either the mapped address (in the case of FI_AV_MAP) or index (FI_AV_TABLE) - is invalid until it is returned again by a new fi_av_insert.

The behavior of operations in progress that reference the removed addresses is undefined.

The use of fi_av_remove is an optimization that applications may use to free memory allocated with addresses that will no longer be accessed. Inserted addresses are not required to be removed. fi_av_close will automatically cleanup any resources associated with addresses remaining in the AV when it is invoked.

fi_av_lookup

This call returns the address stored in the address vector that corresponds to the given fi_addr. The returned address is the same format as those stored by the AV. On input, the addrlen parameter should indicate the size of the addr buffer. If the actual address is larger than what can fit into the buffer, it will be truncated. On output, addrlen is set to the size of the buffer needed to store the address, which may be larger than the input value.

fi_rx_addr

This function is used to convert an endpoint address, returned by fi_av_insert, into an address that specifies a target receive context. The specified fi_addr parameter must either be a value returned from fi_av_insert, in the case of FI_AV_MAP, or an index, in the case of FI_AV_TABLE. The value for rx_ctx_bits must match that specified in the AV attributes for the given address.

Connected endpoints that support multiple receive contexts, but are not associated with address vectors should specify FI_ADDR_NOTAVAIL for the fi_addr parameter.

fi_av_straddr

The fi_av_straddr function converts the provided address into a printable string. The specified address must be of the same format as those stored by the AV, though the address itself is not required to have been inserted. On input, the len parameter should specify the size of the buffer referenced by buf. On output, addrlen is set to the size of the buffer needed to store the address. This size may be larger than the input len. If the provided buffer is too small, the results will be truncated. fi_av_straddr returns a pointer to buf.

NOTES

Providers may implement AV’s using a variety of mechanisms. Specifically, a provider may begin resolving inserted addresses as soon as they have been added to an AV, even if asynchronous operation has been specified. Similarly, a provider may lazily release resources from removed entries.

RETURN VALUES

Insertion calls for an AV opened for synchronous operation will return the number of addresses that were successfully inserted. In the case of failure, the return value will be less than the number of addresses that were specified.

Insertion calls for an AV opened for asynchronous operation (with FI_EVENT flag specified) will return 0 if the operation was successfully initiated. In the case of failure, a negative fabric errno will be returned.

In both the synchronous and asynchronous modes of operation, the fi_addr buffer associated with a failed insertion will be set to FI_ADDR_NOTAVAIL.

All other calls return 0 on success, or a negative value corresponding to fabric errno on error. Fabric errno values are defined in rdma/fi_errno.h.

ERRORS

SEE ALSO

fi_getinfo(3), fi_endpoint(3), fi_domain(3), fi_eq(3)