--- name: "libpfm_itanium" section: "3" platform: "linux" package: "libpfm3-3.2-dev" version: "3.2.070507-1.1" release: "Debian 6.0 (Squeeze)" platforms: ["linux"] url: "https://new.carta.tech/libpfm_itanium" --- # libpfm\_itanium(3) support for Itanium specific PMU features ## NAME libpfm\_itanium - support for Itanium specific PMU features ## SYNOPSIS ``` #include #include int pfm_ita_is_ear(unsigned int i); int pfm_ita_is_dear(unsigned int i); int pfm_ita_is_dear_tlb(unsigned int i); int pfm_ita_is_dear_cache(unsigned int i); int pfm_ita_is_iear(unsigned int i); int pfm_ita_is_iear_tlb(unsigned int i); int pfm_ita_is_iear_cache(unsigned int i); int pfm_ita_is_btb(unsigned int i); int pfm_ita_support_opcm(unsigned int i); int pfm_ita_support_iarr(unsigned int i); int pfm_ita_support_darr(unsigned int i); int pfm_ita_get_event_maxincr(unsigned int i, unsigned int *maxincr); int pfm_ita_get_event_umask(unsigned int i, unsigned long *umask); ``` ## DESCRIPTION The libpfm library provides full support for all the Itanium specific features of the PMU. The interface is defined in **pfmlib\_itanium.h**. It consists of a set of functions and structures which describe and allow access to the Itanium specific PMU features. The Itanium specific functions presented here are mostly used to retrieve the characteristics of an event. Given a opaque event descriptor, obtained by **pfm\_find\_event** or its derivatives, they return a boolean value indicating whether this event support this features or is of a particular kind. The **pfm\_ita\_is\_ear()** function returns 1 if the event designated by **i** corresponds to a EAR event, i.e., an Event Address Register type of events. Otherwise 0 is returned. For instance, **DATA\_EAR\_CACHE\_LAT4** is an ear event, but **CPU\_CYCLES** is not. It can be a data or instruction EAR event. The **pfm\_ita\_is\_dear()** function returns 1 if the event designated by **i** corresponds to an Data EAR event. Otherwise 0 is returned. It can be a cache or TLB EAR event. The **pfm\_ita\_is\_dear\_tlb()** function returns 1 if the event designated by **i** corresponds to a Data EAR TLB event. Otherwise 0 is returned. The **pfm\_ita\_is\_dear\_cache()** function returns 1 if the event designated by **i** corresponds to a Data EAR cache event. Otherwise 0 is returned. The **pfm\_ita\_is\_iear()** function returns 1 if the event designated by **i** corresponds to an instruction EAR event. Otherwise 0 is returned. It can be a cache or TLB instruction EAR event. The **pfm\_ita\_is\_iear\_tlb()** function returns 1 if the event designated by **i** corresponds to an instruction EAR TLB event. Otherwise 0 is returned. The **pfm\_ita\_is\_iear\_cache()** function returns 1 if the event designated by **i** corresponds to an instruction EAR cache event. Otherwise 0 is returned. The **pfm\_ita\_support\_opcm()** function returns 1 if the event designated by **i** supports opcode matching, i.e., can this event be measured accurately when opcode matching via PMC8/PMC9 is active. Not all events supports this feature. The **pfm\_ita\_support\_iarr()** function returns 1 if the event designated by **i** supports code address range restrictions, i.e., can this event be measured accurately when code range restriction is active. Otherwise 0 is returned. Not all events supports this feature. The **pfm\_ita\_support\_darr()** function returns 1 if the event designated by **i** supports data address range restrictions, i.e., can this event be measured accurately when data range restriction is active. Otherwise 0 is returned. Not all events supports this feature. The **pfm\_ita\_get\_event\_maxincr()** function returns in **maxincr** the maximum number of occurrences per cycle for the event designated by **i**. Certain Itanium events can occur more than once per cycle. When an event occurs more than once per cycle, the PMD counter will be incremented accordingly. It is possible to restrict measurement when event occur more than once per cycle. For instance, **NOPS\_RETIRED** can happen up to 6 times/cycle which means that the threshold can be adjusted between 0 and 5, where 5 would mean that the PMD counter would be incremented by 1 only when the nop instruction is executed more than 5 times/cycle. This function returns the maximum number of occurrences of the event per cycle, and is the non-inclusive upper bound for the threshold to program in the PMC register. The **pfm\_ita\_get\_event\_umask()** function returns in **umask** the umask for the event designated by **i**. When the Itanium specific features are needed to support a measurement their descriptions must be passed as model-specific input arguments to the **pfm\_dispatch\_events** call. The Itanium specific input arguments are described in the **pfmlib\_ita\_input\_param\_t** structure and the output parameters in **pfmlib\_ita\_output\_param\_t**. They are defined as follows: ``` typedef enum { PFMLIB_ITA_ISM_BOTH=0, PFMLIB_ITA_ISM_IA32=1, PFMLIB_ITA_ISM_IA64=2 } pfmlib_ita_ism_t; typedef struct { unsigned int flags; unsigned int thres; pfmlib_ita_ism_t ism; } pfmlib_ita_counter_t; typedef struct { unsigned char opcm_used; unsigned long pmc_val; } pfmlib_ita_opcm_t; typedef struct { unsigned char btb_used; unsigned char btb_tar; unsigned char btb_tac; unsigned char btb_bac; unsigned char btb_tm; unsigned char btb_ptm; unsigned char btb_ppm; unsigned int btb_plm; } pfmlib_ita_btb_t; typedef enum { PFMLIB_ITA_EAR_CACHE_MODE= 0, PFMLIB_ITA_EAR_TLB_MODE = 1, } pfmlib_ita_ear_mode_t; typedef struct { unsigned char ear_used; pfmlib_ita_ear_mode_t ear_mode; pfmlib_ita_ism_t ear_ism; unsigned int ear_plm; unsigned long ear_umask; } pfmlib_ita_ear_t; typedef struct { unsigned int rr_plm; unsigned long rr_start; unsigned long rr_end; } pfmlib_ita_input_rr_desc_t; typedef struct { unsigned long rr_soff; unsigned long rr_eoff; } pfmlib_ita_output_rr_desc_t; typedef struct { unsigned int rr_flags; pfmlib_ita_input_rr_desc_t rr_limits[4]; unsigned char rr_used; } pfmlib_ita_input_rr_t; typedef struct { unsigned int rr_nbr_used; pfmlib_ita_output_rr_desc_t rr_infos[4]; pfmlib_reg_t rr_br[8]; } pfmlib_ita_output_rr_t; typedef struct { pfmlib_ita_counter_t pfp_ita_counters[PMU_ITA_NUM_COUNTERS]; unsigned long pfp_ita_flags; pfmlib_ita_opcm_t pfp_ita_pmc8; pfmlib_ita_opcm_t pfp_ita_pmc9; pfmlib_ita_ear_t pfp_ita_iear; pfmlib_ita_ear_t pfp_ita_dear; pfmlib_ita_btb_t pfp_ita_btb; pfmlib_ita_input_rr_t pfp_ita_drange; pfmlib_ita_input_rr_t pfp_ita_irange; } pfmlib_ita_input_param_t; typedef struct { pfmlib_ita_output_rr_t pfp_ita_drange; pfmlib_ita_output_rr_t pfp_ita_irange; } pfmlib_ita_output_param_t; ``` ## INSTRUCTION SET The Itanium processor provides two additional per-event features for counters: thresholding and instruction set selection. They can be set using the **pfp\_ita\_counters** data structure for each event. The **ism** field can be initialized as follows: - **PFMLIB\_ITA\_ISM\_BOTH** The event will be monitored during IA-64 and IA-32 execution - **PFMLIB\_ITA\_ISM\_IA32** The event will only be monitored during IA-32 execution - **PFMLIB\_ITA\_ISM\_IA64** The event will only be monitored during IA-64 execution If **ism** has a value of zero, it will default to PFMLIB\_ITA\_ISM\_BOTH. The **thres** indicates the threshold for the event. A threshold of **n** means that the counter will be incremented by one only when the event occurs more than **n** times per cycle. The **flags** field contains event-specific flags. The currently defined flags are: - PFMLIB\_ITA\_FL\_EVT\_NO\_QUALCHECK When this flag is set it indicates that the library should ignore the qualifiers constraints for this event. Qualifiers includes opcode matching, code and data range restrictions. When an event is marked as not supporting a particular qualifier, it usually means that it is ignored, i.e., the extra level of filtering is ignored. For instance, the CPU\_CYCLES events does not support code range restrictions and by default the library will refuse to program it if range restriction is also requested. Using the flag will override the check and the call to **pfm\_dispatch\_events** will succeed. In this case, CPU\_CYCLES will be measured for the entire program and not just for the code range requested. For certain measurements this is perfectly acceptable as the range restriction will only be applied relevant to events which support it. Make sure you understand which events do not support certains qualifiers before using this flag. ## OPCODE MATCHING The **pfp\_ita\_pmc8** and **pfp\_ita\_pmc9** fields of type **pfmlib\_ita\_opcm\_t** contain the description of what to do with the opcode matchers. Itanium supports opcode matching via PMC8 and PMC9. When this feature is used the **opcm\_used** field must be set to 1, otherwise it is ignored by the library. The **pmc\_val** simply contains the raw value to store in PMC8 or PMC9. The library does not modify the values for PMC8 and PMC9, they will be stored in the **pfp\_pmcs** table of the generic output parameters. ## EVENT ADDRESS REGISTERS The **pfp\_ita\_iear** field of type **pfmlib\_ita\_ear\_t** describes what to do with instruction Event Address Registers (I-EARs). Again if this feature is used the **ear\_used** must be set to 1, otherwise it will be ignored by the library. The **ear\_mode** must be set to either one of **PFMLIB\_ITA\_EAR\_TLB\_MODE**, **PFMLIB\_ITA\_EAR\_CACHE\_MODE**to indicate the type of EAR to program. The umask to store into PMC10 must be in **ear\_umask**. The privilege level mask at which the I-EAR will be monitored must be set in **ear\_plm** which can be any combination of **PFM\_PLM0**, **PFM\_PLM1**, **PFM\_PLM2**, **PFM\_PLM3**. If **ear\_plm** is 0 then the default privilege level mask in **pfp\_dfl\_plm** is used. Finally the instruction set for which to monitor is in **ear\_ism** and can be any one of **PFMLIB\_ITA\_ISM\_BOTH**, **PFMLIB\_ITA\_ISM\_IA32**, or **PFMLIB\_ITA\_ISM\_IA64**. The **pfp\_ita\_dear** field of type **pfmlib\_ita\_ear\_t** describes what to do with data Event Address Registers (D-EARs). The description is identical to the I-EARs except that it applies to PMC11. In general, there are four different methods to program the EAR (data or instruction): - **Method 1** There is an EAR event in the list of events to monitor and **ear\_used** is cleared. In this case the EAR will be programmed (PMC10 or PMC11) based on the information encoded in the event. A counting monitor (PMC4/PMD4-PMC7/PMD7) will be programmed to count DATA\_EAR\_EVENT or INSTRUCTION\_EAR\_EVENTS depending on the type of EAR. - **Method 2** There is an EAR event in the list of events to monitor and **ear\_used** is set. In this case the EAR will be programmed (PMC10 or PMC11) using the information in the **pfp\_ita\_iear** or **pfp\_ita\_dear** structure because it contains more detailed information, such as privilege level and instruction set. A counting monitor (PMC4/PMD4-PMC7/PMD7) will be programmed to count DATA\_EAR\_EVENT or INSTRUCTION\_EAR\_EVENTS depending on the type of EAR. - **Method 3** There is no EAR event in the list of events to monitor and and **ear\_used** is cleared. In this case no EAR is programmed. - **Method 4** There is no EAR event in the list of events to monitor and and **ear\_used** is set. In this case case the EAR will be programmed (PMC10 or PMC11) using the information in the **pfp\_ita\_iear** or **pfp\_ita\_dear** structure. This is the free running mode for the EAR. ## BRANCH TRACE BUFFER The **pfp\_ita\_btb** of type **pfmlib\_ita\_btb\_t** field is used to configure the Branch Trace Buffer (BTB). If the **btb\_used** is set, then the library will take the configuration into account, otherwise any BTB configuration will be ignored. The various fields in this structure provide means to filter out the kind of branches that gets recorded in the BTB. Each one represents an element of the branch architecture of the Itanium processor. Refer to the Itanium specific documentation for more details on the branch architecture. The fields are as follows: - **btb\_tar** If the value of this field is 1, then branches predicted by the Target Address Register (TAR) predictions are captured. If 0 no branch predicted by the TAR is included. - **btb\_tac** If this field is 1, then branches predicted by the Target Address Cache (TAC) are captured. If 0 no branch predicted by the TAC is included. - **btb\_bac** If this field is 1, then branches predicted by the Branch Address Corrector (BAC) are captured. If 0 no branch predicted by the BAC is included. - **btb\_tm** If this field is 0, then no branch is captured. If this field is 1, then non taken branches are captured. If this field is 2, then taken branches are captured. Finally if this field is 3 then all branches are captured. - **btb\_ptm** If this field is 0, then no branch is captured. If this field is 1, then branches with a mispredicted target address are captured. If this field is 2, then branches with correctly predicted target address are captured. Finally if this field is 3 then all branches are captured regardless of target address prediction. - **btb\_ppm** If this field is 0, then no branch is captured. If this field is 1, then branches with a mispredicted path (taken/non taken) are captured. If this field is 2, then branches with correctly predicted path are captured. Finally if this field is 3 then all branches are captured regardless of their path prediction. - **btb\_plm** This is the privilege level mask at which the BTB captures branches. It can be any combination of **PFM\_PLM0**, **PFM\_PLM1**, **PFM\_PLM2**, **PFM\_PLM3**. If **btb\_plm** is 0 then the default privilege level mask in **pfp\_dfl\_plm** is used. There are 4 methods to program the BTB and they are as follows: - **Method 1** The **BRANCH\_EVENT** is in the list of events to monitor and **btb\_used** is cleared. In this case, the BTB will be configured (PMC12) to record ALL branches. A counting monitor (PMC4/PMD4-PMC7/PMD7) will be programmed to count **BRANCH\_EVENT**. - **Method 2** The **BRANCH\_EVENT** is in the list of events to monitor and **btb\_used** is set. In this case, the BTB will be configured (PMC12) using the information in the **pfp\_ita\_btb** structure. A counting monitor (PMC4/PMD4-PMC7/PMD7) will be programmed to count **BRANCH\_EVENT**. - **Method 3** The **BRANCH\_EVENT** is not in the list of events to monitor and **btb\_used** is set. In this case, the BTB will be configured (PMC12) using the information in the **pfp\_ita\_btb** structure. This is the free running mode for the BTB. - **Method 4** The **BRANCH\_EVENT** is not in the list of events to monitor and **btb\_used** is cleared. In this case, the BTB is not programmed. ## DATA AND CODE RANGE RESTRICTIONS The **pfp\_ita\_drange** and **pfp\_ita\_irange** fields control the range restrictions for the data and code respectively. The idea is that the application passes a set of ranges, each designated by a start and end address. Upon return from **pfm\_dispatch\_events()**, the application gets back the set of registers and their values that needs to be programmed via a kernel interface. Range restriction is implemented using the debug registers. There is a limited number of debug registers and they go in pair. With 8 data debug registers, a maximum of 4 distinct ranges can be specified. The same applies to code range restrictions. Moreover, there are some severe constraints on the alignment and size of the range. Given that the size range is specified using a bitmask, there can be situations where the actual range is larger than the requested range. The library will make the best effort to cover only what is requested. It will never cover less than what is requested. The algorithm uses more than one pair of debug registers to get a more precise range if necessary. Hence, up to the 4 pairs can be used to describe a single range. The library returns the start and end offsets of the actual range compared to the requested range. If range restriction is to be used, the **rr\_used** field must be set to one, otherwise settings will be ignored. The ranges are described by the **pfmlib\_ita2\_input\_rr\_t** structure. Up to 4 ranges can be defined. Each range is described in by a entry in **rr\_limits**. The **pfmlib\_ita2\_input\_rr\_desc\_t** structure is defined as follows: - **rr\_plm** The privilege level at which the range is active. It can be any combinations of **PFM\_PLM0**, **PFM\_PLM1**, **PFM\_PLM2**, **PFM\_PLM3**. If **rr\_plm** is 0 then the default privilege level mask in **pfp\_dfl\_plm** is used.The privilege level is only relevant for code ranges, data ranges ingores the setting. - **rr\_start** This is the start address of the range. Any address is supported but for code range it must be bundle aligned, i.e., 16-byte aligned. - **rr\_end** This is the end address of the range. Any address is supported but for code range it must be bundle aligned, i.e., 16-byte aligned. The library will provide the values for the debug registers as well as some information about the actual ranges in the output parameters and more precisely in the **pfmlib\_ita2\_output\_rr\_t** structure for each range. The structure is defined as follows: - **rr\_nbr\_used** Contains the number of debug registers used to cover the range. This is necessarily an even number as debug registers always go in pair. The value of this field is between 0 and 7. - **rr\_br** This table contains the list of debug registers necessary to cover the ranges. Each element is of type **pfmlib\_reg\_t**. The **reg\_num** field contains the debug register index while **reg\_value** contains the debug register value. Both the index and value must be copied into the kernel specific argument to program the debug registers. The library never programs them. - **rr\_infos** Contains information about the ranges defined. Because of alignment restrictions, the actual range covered by the debug registers may be larger than the requested range. This table describe the differences between the requested and actual ranges expressed as offsets: - **rr\_soff** Contains the start offset of the actual range described by the debug registers. If zero, it means the library was able to match exactly the beginning of the range. Otherwise it represents the number of byte by which the actual range preceeds the requested range. - **rr\_eoff** Contains the end offset of the actual range described by the debug registers. If zero, it means the library was able to match exactly the end of the range. Otherwise it represents the number of bytes by which the actual range exceeds the requested range. ## ERRORS Refer to the description of **pfm\_dispatch\_events()** for errors when using the Itanium specific input and output arguments. ## SEE ALSO [pfm\_dispatch\_events(3)](/pfm_dispatch_events/3.md) and set of examples shipped with the library ## AUTHOR Stephane Eranian \