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Add domain structure to object hierarchy
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It turns out that with the domain being the primary boundary of
threading in libfabric, it's not great assuming a 1:1 device to
domain mapping.  We previously hacked something up to make
the domain be part of the endpoint, sometimes, but that makes
for some really icky code.

This patch adds a domain structure to the object hierarchy and
unifies the when to create a new domain code between the two
transports.

Signed-off-by: Brian Barrett <[email protected]>
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bwbarrett committed Oct 26, 2024
1 parent 938668b commit 1573bf6
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Showing 6 changed files with 699 additions and 332 deletions.
139 changes: 106 additions & 33 deletions include/nccl_ofi.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -132,6 +132,7 @@ extern size_t system_page_size;

struct nccl_net_ofi_plugin;
struct nccl_net_ofi_device;
struct nccl_net_ofi_domain;
struct nccl_net_ofi_ep;
struct nccl_net_ofi_req;
struct nccl_net_ofi_mr_handle;
Expand All @@ -142,6 +143,7 @@ struct nccl_net_ofi_recv_comm;

typedef struct nccl_net_ofi_plugin nccl_net_ofi_plugin_t;
typedef struct nccl_net_ofi_device nccl_net_ofi_device_t;
typedef struct nccl_net_ofi_domain nccl_net_ofi_domain_t;
typedef struct nccl_net_ofi_ep nccl_net_ofi_ep_t;
typedef struct nccl_net_ofi_req nccl_net_ofi_req_t;
typedef struct nccl_net_ofi_mr_handle nccl_net_ofi_mr_handle_t;
Expand Down Expand Up @@ -232,11 +234,8 @@ typedef struct nccl_ofi_properties {
* Device Data
*
* A device is roughly a NIC (or a port on a NIC) or a multi-rail
* group. While a multi-threaded app may create multiple endpoints
* per device, the device data should be shared across multiple
* threads in the same process. Sharable structures such as address
* vectors, fabrics, and domains should be associated with a device
* instead of an endpoint.
* group. The device is the unit of bandwidth sharing and general NIC
* propoeries, and accessing domains (ie, groups of NIC resources).
*/
struct nccl_net_ofi_device {
struct nccl_net_ofi_plugin *plugin;
Expand All @@ -251,37 +250,22 @@ struct nccl_net_ofi_device {
*/
char *name;

/*
* Protocol-agnostic MR cache for this device. Note that Registrations
* are tied to domains in libfabric, but we do not have a
* domain-specific object today, so stashing it in the device itself.
* This should change if we were to break up nccl_net_ofi_device into
* separate device and domain objects.
*/
nccl_ofi_mr_cache_t *mr_cache;

/* do we need to use an mr rkey pool? This is a
* provider-specific behavior determined when providers are
* selected.
*/
bool need_mr_rkey_pool;

/* Memory registration key pool */
nccl_ofi_idpool_t mr_rkey_pool;

int (*get_properties)(nccl_net_ofi_device_t *base_dev,
nccl_ofi_properties_t *props);

/*
* @brief Get nccl_ofi_ep for given
* nccl_ofi_device. Create if it does not exist. Store
* in pthread key. Increase reference counter. Must be
* protected by lock stored in device.
*
* During the plugin initialization, this function will be
* called once per process using one of the instantiated device structs
* to create and configure the endpoint of the initializing thread.
/* Retrieve a domain associated with this device. There may
* be more than one domain per device, depending on a number
* of performance tradeoffs (be sure to read the domain
* description below).
*/
nccl_net_ofi_domain_t *(*get_domain)(nccl_net_ofi_device_t *dev);

int (*get_ep)(nccl_net_ofi_device_t *base_dev,
nccl_net_ofi_ep_t **ep);

Expand All @@ -293,25 +277,93 @@ struct nccl_net_ofi_device {
*/
int (*release)(nccl_net_ofi_device_t *device);

/* Lock for concurrency since endpoints can be shared by
/* Lock for concurrency since domains can be shared by
* multiple entities. */
pthread_mutex_t device_lock;

/* private */
/**
* Create a new endpoint
/*
* create a new domain. This funcion is a private pure
* virtual function, which is called from the base
* implementation of get_domain() and should not be called
* from the more general case.
*/
nccl_net_ofi_domain_t *(*create_domain)(nccl_net_ofi_device_t *dev);

/*
* hash table indexed by thread id of active domains.
*/
nccl_net_ofi_domain_t *domain_table;
};


/**
* Domain Object - Represents a protection and thread safety domain
*
* A domain is a weird combination of a Libfabric domain (and related
* resources like an AV and CQ) as well as a general thread boundary.
* Transports are free to implement fine grained threads, but
* generally it is expected that calls into resources that share the
* same domain will share the same lock.
*/
struct nccl_net_ofi_domain {
/* Backpointer to the device associated with this domain. */
nccl_net_ofi_device_t *device;

/*
* Retrieve an endpoint for this domain. If a suitable
* endpoint does not exist, call create_endpoint() to create
* one and return that endpoint. This function is a pure
* virtual function that must be implemented by inheriting
* classes.
*/
int (*get_ep)(nccl_net_ofi_domain_t *domain,
nccl_net_ofi_ep_t **endpoint);

/*
* Destructor - release resources associated with the domain
*/
int (*release)(nccl_net_ofi_domain_t *domain);

/*
* Protocol-agnostic MR cache for this device.
*/
nccl_ofi_mr_cache_t *mr_cache;

/* Memory registration key pool */
nccl_ofi_idpool_t mr_rkey_pool;


pthread_mutex_t domain_lock;

/* Private */
/* pure virtual function called when resources associated with
* the ep should be destroyed. Device lock will be held when
* this function is called.
*/
int (*free)(nccl_net_ofi_domain_t *domain);

/* Create a new endpoint
*
* Pure virtual function to allocate a new endpoint structure
*/
int (*create_endpoint)(nccl_net_ofi_device_t *device,
int (*create_endpoint)(nccl_net_ofi_domain_t *domain,
nccl_net_ofi_ep_t **ep);

/* hash table of active endpoints. We reuse endpoints based
* on the thread that calls get_ep().
*/
nccl_net_ofi_ep_t *endpoint_table;

/* thread id of the thread that called get_domain(). Used as
the hash key for the domain hash */
long creating_thread_id;

/* hash table handle */
UT_hash_handle hh;
};


/**
* Endpoint - A per-Proxy Thread device abstraction
*
Expand All @@ -328,8 +380,8 @@ struct nccl_net_ofi_device {
* implementation.
*/
struct nccl_net_ofi_ep {
/* Backpointer to the device associated with this ep. */
nccl_net_ofi_device_t *device;
/* Backpointer to the domain associated with this ep. */
nccl_net_ofi_domain_t *domain;

/* Create a receiving object and provide a handle to it.
*
Expand Down Expand Up @@ -558,12 +610,33 @@ struct nccl_net_ofi_plugin {
*/
int nccl_net_ofi_create_plugin(nccl_net_ofi_plugin_t **plugin_p);

/* base implementation of endpoint release. endpoint_init() will set
* the release pointer to this function, although transports can
* override that function pointer and later call this function
* directly.
*/
int nccl_net_ofi_endpoint_release(nccl_net_ofi_ep_t *ep);

int nccl_net_ofi_endpoint_init(nccl_net_ofi_device_t *device, nccl_net_ofi_ep_t *ep);
/* initialize resources associated with the endpoint base class.
* Expectation is that this will be called by a transport's endpoint
* creation function */
int nccl_net_ofi_endpoint_init(nccl_net_ofi_domain_t *domain, nccl_net_ofi_ep_t *ep);

/* free resources associated with the endpoint base class.
* Expectation is that this will be called by a transport's endpoint
* free function. */
int nccl_net_ofi_endpoint_fini(nccl_net_ofi_ep_t *ep);

/* initialize resources associated with the domain base class.
* Expectation is that this will be called by a transport's domain
* creation routine */
int nccl_net_ofi_domain_init(nccl_net_ofi_device_t *device, nccl_net_ofi_domain_t *domain);

/* free resources associated with the domain base class. Expectation
* is that this will be called by a transport's domain free
* function. */
int nccl_net_ofi_domain_fini(nccl_net_ofi_domain_t *domain);

/**
* Constructor for a device object
*/
Expand Down
31 changes: 22 additions & 9 deletions include/nccl_ofi_rdma.h
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Original file line number Diff line number Diff line change
Expand Up @@ -750,12 +750,6 @@ typedef struct nccl_net_ofi_rdma_device_rail {

/* Fabric handle */
struct fid_fabric *fabric;

/* Access domain handles */
struct fid_domain *domain;

/* Completion Queue handle */
struct fid_cq *cq;
} nccl_net_ofi_rdma_device_rail_t;

/*
Expand Down Expand Up @@ -806,15 +800,34 @@ typedef struct nccl_net_ofi_rdma_device {

bool use_long_rkeys;

/* List of endpoints and set of addresses they have connections to */
nccl_ofi_ep_addr_list_t *ep_addr_list;

#if HAVE_NVTX_TRACING
nvtxDomainHandle_t nvtx_domain[MAX_NUM_RAILS];
#endif
} nccl_net_ofi_rdma_device_t;


typedef struct nccl_net_ofi_rdma_domain_rail {
/* Access domain handles */
struct fid_domain *domain;

struct fid_cq *cq;
} nccl_net_ofi_rdma_domain_rail_t;


typedef struct nccl_net_ofi_rdma_domain {
nccl_net_ofi_domain_t base;

int num_rails;
nccl_net_ofi_rdma_domain_rail_t *domain_rails;

/* Memory registration key pool */
nccl_ofi_idpool_t key_pool;

/* List of endpoints and set of addresses they have connections to */
nccl_ofi_ep_addr_list_t *ep_addr_list;
} nccl_net_ofi_rdma_domain_t;


struct nccl_net_ofi_rdma_plugin {
nccl_net_ofi_plugin_t base;

Expand Down
20 changes: 14 additions & 6 deletions include/nccl_ofi_sendrecv.h
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Original file line number Diff line number Diff line change
Expand Up @@ -111,16 +111,27 @@ typedef struct nccl_net_ofi_sendrecv_ep {
/* Endpoint handle to communicate to */
struct fid_ep *ofi_ep;

/* Access Domain handle */
struct fid_domain *domain;

/* Address vector handle */
struct fid_av *av;

/* Completion Queue handle */
struct fid_cq *cq;
} nccl_net_ofi_sendrecv_ep_t;


/*
* Domain - container for the libfabric domain, which is the threading
* boundary for most Libfabric providers, given how the util cq
* implementation works.
*/
typedef struct nccl_net_ofi_sendrecv_domain {
nccl_net_ofi_domain_t base;

/* Access Domain handle */
struct fid_domain *domain;
} nccl_net_ofi_sendrecv_domain_t;


/**
* @brief Sendrecv Device
*
Expand Down Expand Up @@ -163,9 +174,6 @@ typedef struct nccl_net_ofi_sendrecv_device {

/* Fabric handle */
struct fid_fabric *fabric;

/* Access Domain handle */
struct fid_domain *domain;
} nccl_net_ofi_sendrecv_device_t;

typedef struct nccl_net_ofi_sendrecv_req {
Expand Down
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