Provided by: libfabric-dev_1.6.2-3ubuntu0.1_amd64 
NAME
fi_cntr - Completion and event counter operations
fi_cntr_open / fi_close : Allocate/free a counter
fi_cntr_read : Read the current value of a counter
fi_cntr_readerr : Reads the number of operations which have completed in error.
fi_cntr_add : Increment a counter by a specified value
fi_cntr_set : Set a counter to a specified value
fi_cntr_wait : Wait for a counter to be greater or equal to a threshold value
SYNOPSIS
#include <rdma/fi_domain.h>
int fi_cntr_open(struct fid_domain *domain, struct fi_cntr_attr *attr,
struct fid_cntr **cntr, void *context);
int fi_close(struct fid *cntr);
uint64_t fi_cntr_read(struct fid_cntr *cntr);
uint64_t fi_cntr_readerr(struct fid_cntr *cntr);
int fi_cntr_add(struct fid_cntr *cntr, uint64_t value);
int fi_cntr_adderr(struct fid_cntr *cntr, uint64_t value);
int fi_cntr_set(struct fid_cntr *cntr, uint64_t value);
int fi_cntr_seterr(struct fid_cntr *cntr, uint64_t value);
int fi_cntr_wait(struct fid_cntr *cntr, uint64_t threshold,
int timeout);
ARGUMENTS
domain : Fabric domain
cntr : Fabric counter
attr : Counter attributes
context : User specified context associated with the counter
value : Value to increment or set counter
threshold : Value to compare counter against
timeout : Time in milliseconds to wait. A negative value indicates infinite timeout.
DESCRIPTION
Counters record the number of requested operations that have completed. Counters can provide a
light-weight completion mechanism by suppressing the generation of a full completion event. They are
useful for applications that only need to know the number of requests that have completed, and not
details about each request. For example, counters may be useful for implementing credit based flow
control or tracking the number of remote processes which have responded to a request.
Counters typically only count successful completions. However, if an operation completes in error, it
may increment an associated error value. That is, a counter actually stores two distinct values, with
error completions updating an error specific value.
fi_cntr_open
fi_cntr_open allocates a new fabric counter. The properties and behavior of the counter are defined by
struct fi_cntr_attr.
struct fi_cntr_attr {
enum fi_cntr_events events; /* type of events to count */
enum fi_wait_obj wait_obj; /* requested wait object */
struct fid_wait *wait_set; /* optional wait set */
uint64_t flags; /* operation flags */
};
events : A counter captures different types of events. The specific type which is to counted are one of
the following:
• FI_CNTR_EVENTS_COMP : The counter increments for every successful completion that occurs on an
associated bound endpoint. The type of completions -- sends and/or receives -- which are counted may
be restricted using control flags when binding the counter and the endpoint. Counters increment on all
successful completions, separately from whether the operation generates an entry in an event queue.
wait_obj : Counters may be associated with a specific wait object. Wait objects allow applications to
block until the wait object is signaled, indicating that a counter has reached a specific threshold.
Users may use fi_control to retrieve the underlying wait object associated with a counter, in order to
use it in other system calls. The following values may be used to specify the type of wait object
associated with a counter: FI_WAIT_NONE, FI_WAIT_UNSPEC, FI_WAIT_SET, FI_WAIT_FD, and FI_WAIT_MUTEX_COND.
The default is FI_WAIT_NONE.
• FI_WAIT_NONE : Used to indicate that the user will not block (wait) for events on the counter.
• FI_WAIT_UNSPEC : Specifies that the user will only wait on the counter using fabric interface calls,
such as fi_cntr_wait. In this case, the underlying provider may select the most appropriate or highest
performing wait object available, including custom wait mechanisms. Applications that select
FI_WAIT_UNSPEC are not guaranteed to retrieve the underlying wait object.
• FI_WAIT_SET : Indicates that the event counter should use a wait set object to wait for events. If
specified, the wait_set field must reference an existing wait set object.
• FI_WAIT_FD : Indicates that the counter should use a file descriptor as its wait mechanism. A file
descriptor wait object must be usable in select, poll, and epoll routines. However, a provider may
signal an FD wait object by marking it as readable, writable, or with an error.
• FI_WAIT_MUTEX_COND : Specifies that the counter should use a pthread mutex and cond variable as a wait
object.
wait_set : If wait_obj is FI_WAIT_SET, this field references a wait object to which the event counter
should attach. When an event is added to the event counter, the corresponding wait set will be signaled
if all necessary conditions are met. The use of a wait_set enables an optimized method of waiting for
events across multiple event counters. This field is ignored if wait_obj is not FI_WAIT_SET.
flags : Flags are reserved for future use, and must be set to 0.
fi_close
The fi_close call releases all resources associated with a counter. When closing the counter, there must
be no opened endpoints, transmit contexts, receive contexts or memory regions associated with the
counter. If resources are still associated with the counter when attempting to close, the call will
return -FI_EBUSY.
fi_cntr_control
The fi_cntr_control call is used to access provider or implementation specific details of the counter.
Access to the counter should be serialized across all calls when fi_cntr_control is invoked, as it may
redirect the implementation of counter operations. The following control commands are usable with a
counter:
FI_GETOPSFLAG (uint64_t *) : Returns the current default operational flags associated with the counter.
FI_SETOPSFLAG (uint64_t *) : Modifies the current default operational flags associated with the counter.
FI_GETWAIT (void **) : This command allows the user to retrieve the low-level wait object associated with
the counter. The format of the wait-object is specified during counter creation, through the counter
attributes. See fi_eq.3 for addition details using control with FI_GETWAIT.
fi_cntr_read
The fi_cntr_read call returns the current value of the counter.
fi_cntr_readerr
The read error call returns the number of operations that completed in error and were unable to update
the counter.
fi_cntr_add
This adds the user-specified value to the counter.
fi_cntr_adderr
This adds the user-specified value to the error value of the counter.
fi_cntr_set
This sets the counter to the specified value.
fi_cntr_seterr
This sets the error value of the counter to the specified value.
fi_cntr_wait
This call may be used to wait until the counter reaches the specified threshold, or until an error or
timeout occurs. Upon successful return from this call, the counter will be greater than or equal to the
input threshold value.
If an operation associated with the counter encounters an error, it will increment the error value
associated with the counter. Any change in a counter's error value will unblock any thread inside
fi_cntr_wait.
If the call returns due to timeout, -FI_ETIMEDOUT will be returned. The error value associated with the
counter remains unchanged.
It is invalid for applications to call this function if the counter has been configured with a wait
object of FI_WAIT_NONE or FI_WAIT_SET.
RETURN VALUES
Returns 0 on success. On error, a negative value corresponding to fabric errno is returned.
fi_cntr_read / fi_cntr_readerr : Returns the current value of the counter.
Fabric errno values are defined in rdma/fi_errno.h.
NOTES
In order to support a variety of counter implementations, updates made to counter values (e.g.
fi_cntr_set or fi_cntr_add) may not be immediately visible to counter read operations (i.e. fi_cntr_read
or fi_cntr_readerr). A small, but undefined, delay may occur between the counter changing and the
reported value being updated. However, a final updated value will eventually be reflected in the read
counter value, with the order of the updates maintained.
SEE ALSO
fi_getinfo(3), fi_endpoint(3), fi_domain(3), fi_eq(3), fi_poll(3)
AUTHORS
OpenFabrics.
Libfabric Programmer's Manual 2017-09-14 fi_cntr(3)