% PT_QRY_TIME(3)

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# NAME

pt_qry_time, pt_qry_core_bus_ratio, pt_insn_time, pt_insn_core_bus_ratio,

pt_blk_time, pt_blk_core_bus_ratio - query an Intel(R) Processor Trace decoder

for timing information

# SYNOPSIS

| **\#include `<intel-pt.h>`**

|

| **int pt_qry_time(struct pt_query_decoder \**decoder*, uint64_t \**time*,**

|                 **uint32_t \**lost_mtc*, uint32_t \**lost_cyc*);**

| **int pt_qry_core_bus_ratio(struct pt_query_decoder \**decoder*,**

|                           **uint32_t \**cbr*);**

|

| **int pt_insn_time(struct pt_insn_decoder \**decoder*, uint64_t \**time*,**

|                  **uint32_t \**lost_mtc*, uint32_t \**lost_cyc*);**

| **int pt_insn_core_bus_ratio(struct pt_insn_decoder \**decoder*,**

|                            **uint32_t \**cbr*);**

|

| **int pt_blk_time(struct pt_block_decoder \**decoder*, uint64_t \**time*,**

|                 **uint32_t \**lost_mtc*, uint32_t \**lost_cyc*);**

| **int pt_blk_core_bus_ratio(struct pt_block_decoder \**decoder*,**

|                           **uint32_t \**cbr*);**

Link with *-lipt*.

# DESCRIPTION

**pt_qry_time**(), **pt_insn_time**(), and **pt_blk_time**() provide the current

estimated timestamp count (TSC) value in the unsigned integer variable pointed

to by the *time* argument.  The returned value corresponds to what an **rdtsc**

instruction would have returned.

At configurable intervals, Intel PT contains the full, accurate TSC value.

Between those intervals, the timestamp count is estimated using a collection of

lower-bandwidth packets, the Mini Time Counter (MTC) packet and the Cycle Count

Packet (CYC).  Depending on the Intel PT configuration, timing can be very

precise at the cost of increased bandwidth or less precise but requiring lower

bandwidth.

The decoder needs to be calibrated in order to translate Cycle Counter ticks

into Core Crystal Clock ticks.  Without calibration, CYC packets need to be

dropped.  The decoder calibrates itself using MTC, CYC, and CBR packets.

To interpret MTC and CYC packets, the decoder needs additional information

provided in respective fields in the *pt_config* structure.  Lacking this

information, MTC packets may need to be dropped.  This will impact the precision

of the estimated timestamp count by losing periodic updates and it will impact

calibration, which may result in reduced precision for cycle-accurate timing.

The number of dropped MTC and CYC packets gives a rough idea about the quality

of the estimated timestamp count.  The value of dropped MTC and CYC packets is

given in the unsigned integer variables pointed to by the *lost_mtc* and

*lost_cyc* arguments respectively.  If one or both of the arguments is NULL, no

information on lost packets is provided for the respective packet type.

**pt_qry_core_bus_ratio**(), **pt_insn_core_bus_ratio**(), and

**pt_blk_core_bus_ratio**() give the last known core:bus ratio as provided by

the Core Bus Ratio (CBR) Intel PT packet.

# RETURN VALUE

All functions return zero on success or a negative *pt_error_code* enumeration

constant in case of an error.

# ERRORS

pte_invalid

:   The *decoder* or *time* (**pt_qry_time**(), **pt_insn_time**(), and

    **pt_blk_time**()) or *cbr* (**pt_qry_core_bus_ratio**(),

    **pt_insn_core_bus_ratio**(), and **pt_blk_core_bus_ratio**()) argument is

    NULL.

pte_no_time

:   There has not been a TSC packet to provide the full, accurate Time Stamp

    Count.  There may have been MTC or CYC packets, so the provided *time* may

    be non-zero.  It is zero if there has not been any timing packet yet.

    Depending on the Intel PT configuration, TSC packets may not have been

    enabled.  In this case, the *time* value provides the relative time based on

    other timing packets.

pte_no_cbr

:   There has not been a CBR packet to provide the core:bus ratio.  The *cbr*

    value is undefined in this case.

# NOTES

All decoders read ahead.  The estimated timestamp count and core:bus ratios

correspond to their current decode position, which may be ahead of the trace

position that matches the last event, instruction, or block.

The query decoder also provides an estimated timestamp count in the *pt_event*

structure.

# SEE ALSO

**pt_qry_alloc_decoder**(3), **pt_qry_free_decoder**(3),

**pt_qry_cond_branch**(3), **pt_qry_indirect_branch**(3), **pt_qry_event**(3),

**pt_insn_alloc_decoder**(3), **pt_insn_free_decoder**(3), **pt_insn_next**(3),

**pt_blk_alloc_decoder**(3), **pt_blk_free_decoder**(3), **pt_blk_next**(3)