man pages section 3: Extended Library Functions, Volume 1

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Updated: July 2014
 
 

cpc_set_add_request(3CPC)

Name

cpc_set_create, cpc_set_destroy, cpc_set_add_request, cpc_walk_requests - manage sets of counter requests

Synopsis

cc [ flag… ] file
–lcpc [ library… ] 
#include <libcpc.h>

cpc_set_t *cpc_set_create(
cpc_t *cpc);
int cpc_set_destroy(
cpc_t *cpc, cpc_set_t *
set);
int cpc_set_add_request(
cpc_t *cpc, cpc_set_t *
set,
     const char *event, 
uint64_t preset, uint_t 
flags,
     uint_t nattrs, const cpc_attr_t *
attrs);
void cpc_walk_requests(
cpc_t *cpc, cpc_set_t *
set, void *arg,
     void (*action)(void *
arg, int index, const char *
event,
     uint64_t preset, uint_t flags, int 
nattrs,
     const cpc_attr_t *attrs));

Description

The cpc_set_create() function returns an initialized and empty CPC set. A CPC set contains some number of requests, where a request represents a specific configuration of a hardware performance instrumentation counter or hardware sampling present on the processor. The cpc_set_t data structure is opaque and must not be accessed directly by the application.

Applications wanting to program one or more performance counters and hardware sampling must create an empty set with cpc_set_create () and add requests to the set with cpc_set_add_request (). Once all requests have been added to a set, the set must be bound to the hardware performance counters (see cpc_bind_curlwp (), cpc_bind_pctx(), and cpc_bind_cpu (), all described on cpc_bind_curlwp(3CPC)) before counting events. At bind time, the system attempts to match each request with an available physical counter capable of counting the event specified in the request. If the bind is successful, a 64-bit virtualized counter is created to store the counts accumulated by the hardware counter for the CPC request and the sampling buffer is created to store the sampling results for the SMPL request. These are stored and managed in CPC buffers separate from the CPC set whose requests are being counted. See cpc_buf_create(3CPC) and cpc_set_sample(3CPC).

The cpc_set_add_request() function specifies a configuration of a hardware counter and a hardware sampling. The arguments to cpc_set_add_request() are:

event

A string containing the name of an event supported by the system's processor. The cpc_walk_events_all(), cpc_walk_events_all_common(), cpc_walk_events_pic(), and cpc_walk_events_pic_common() functions (all described on cpc_npic(3CPC)) can be used to query the processor for the names of available events. Certain processors allow the use of raw event codes, in which case a string representation of an event code in a form acceptable to strtol(3C) can be used as the event argument.

preset

The value with which the system initializes the counter.

flags

Three flags are defined that modify the behavior of the counter acting on behalf of this request:

CPC_COUNT_USER

The counter should count events that occur while the processor is in user mode.

CPC_COUNT_SYSTEM

The counter should count events that occur while the processor is in privileged mode.

CPC_OVF_NOTIFY_EMT

For a CPU performance counter (CPC) request, you can request a signal to be sent to the application when the physical counter overflows. A SIGEMT signal is delivered if the processor is capable of delivering an interrupt when the counter counts past its maximum value. All CPC requests in the set containing the counter that overflowed are stopped until the set is rebound.

For a hardware sampling (SMPL) request, you can request a signal to be sent to the application when the specified number of SMPL records for the SMPL request have been collected. A SIGEMT signal is delivered if the processor is capable of delivering an interrupt when a certain number of SMPL records have been collected. SMPL requests will not be stopped even after any SMPL request in the set has collected the requested number of SMPL records and the counter associated with any CPC request in the set overflowed.

CPC_HW_SMPL

When adding a hardware sampling ( SMPL) request, this flag must be specified. When adding a CPU performance counter (CPC) request, this flag should not be specified.

At least one of CPC_COUNT_USER or CPC_COUNT_SYSTEM must be specified to program the hardware for counting.

nattrs, attrs

The nattrs argument specifies the number of attributes pointed to by the attrs argument, which is an array of cpc_attr_t structures containing processor-specific attributes that modify the request's configuration. The cpc_walk_attrs() and cpc_walk_attrs_common () functions (see cpc_npic(3CPC)) can be used to query the processor for the list of attributes it accepts. The library makes a private copy of the attrs array, allowing the application to dispose of it immediately after calling cpc_set_add_request ().

When adding a SMPL request, the number of SMPL records to collect must be requested by using the smpl_nrecs attribute, which should be an integer value greater than 0 and equal to or smaller than the supported maximum value returned by cpc_get_max_smpl_rec_count () function.

The cpc_walk_requests() function calls the action function on each request that has been added to the set. The arg argument is passed unmodified to the action function with each call. The flag argument passed to action function will include CPC_HW_SMPL flag for a SMPL request. Note that the flag is not included for a CPC request.

Return Values

Upon successful completion, cpc_set_create() returns a handle to the opaque cpc_set_t data structure. Otherwise, NULL is returned and errno is set to indicate the error.

Upon successful completion, cpc_set_destroy() returns 0. Otherwise, -1 is returned and errno is set to indicate the error.

Upon successful completion, cpc_set_add_request() returns an integer index used to refer to the data generated by that request during data retrieval. Otherwise, -1 is returned and errno is set to indicate the error.

Errors

These functions will fail if:

EINVAL

An event, attribute, or flag passed to cpc_set_add_request () was invalid.

For cpc_set_destroy() and cpc_set_add_request (), the set parameter was not created with the given cpc_t.

ENOMEM

There was not enough memory available to the process to create the library's data structures.

Attributes

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Interface Stability
Committed
MT-Level
Safe

See Also

cpc_bind_curlwp(3CPC), cpc_buf_create(3CPC), cpc_npic(3CPC), cpc_seterrhndlr(3CPC), libcpc(3LIB), strtol(3C), attributes(5)

Notes

The system automatically determines which particular physical counter to use to count the events specified by each request. Applications can force the system to use a particular counter by specifying the counter number in an attribute named picnum that is passed to cpc_set_add_request(). Counters are numbered from 0 to n - 1, where n is the number of counters in the processor as returned by cpc_npic(3CPC) for a CPC request and by cpc_npic(3CPC) for a SMPL request.

Some processors, such as UltraSPARC, do not allow the hardware counters to be programmed differently. In this case, all requests in the set must have the same configuration, or an attempt to bind the set will return EINVAL. If a cpc_errhndlr_t has been registered with cpc_seterrhndlr(3CPC), the error handler is called with subcode CPC_CONFLICTING_REQS. For example, on UltraSPARC pic0 and pic1 must both program events in the same processor mode (user mode, kernel mode, or both). For example, pic0 cannot be programmed with CPC_COUNT_USER while pic1 is programmed with CPC_COUNT_SYSTEM. Refer to the hardware documentation referenced by cpc_cpuref(3CPC) for details about a particular processor's performance instrumentation hardware.