NAME

prof − Analyzes profile data

SYNOPSIS

prof [PC-sampling_options] [prog_name
 [PC-sampling_data_file]... ]

prof −pixie [pixie_options]  [prog_name
 [Addrs_file|Counts_file]... ]

prof −pixstats [pixstats_options] [prog_name
 [Addrs_file|Counts_file]... ]

PARAMETERS

prog_name
Name of the program executable to be profiled.  This program should be compiled with the −g1, −g2, or −g3 flag to obtain more complete profiling information.  If the default symbol table level (−g0) has been used, line number information, static procedure names, and file names are unavailable to the profiling code. 

FLAGS

For each prof option, you need to type only enough of the name to distinguish it from the other options.  If you do not specify any options, prof uses −procedures by default. Always specify −pixie  or −pixstats when you process .Addrs and .Counts files. 

The prof command accepts the following options:

−allCauses the profiles for all shared libraries (if any) described in the data file(s) to be displayed, in addition to the profile for the executable. 

−asmCauses the profiler to print the assembly instructions for each subroutine along with the cycle counts for each instruction.  The subroutines are sorted from highest cycle count to lowest.  The instructions for each subroutine are printed in order; they are not sorted by cycle count.  (Use this flag only with the −pixie flag.) 

−clock megahertz
Alters the appropriate parts of the listing to reflect the clock speed of the CPU. (Use this flag only with the −pixie flag.) 

−disassemble
Disassembles and shows the analyzed object code. (Use this flag only with the −pixstats flag.) 

−dislimit f
Limits the disassembly to blocks with f% frequency.  (Use this flag only with the −pixstats flag.) 

−exclude procedure_name
If you use one or more −exclude options, the profiler omits the specified procedure and its descendents from the listing. If any option uses an uppercase “E” (for “Exclude”), prof also omits that procedure from the base upon which it calculates percentages. 

−excobj object_file_name
Causes the profile for the named executable or shared library not to be printed.  You can use this flag multiple times in a single prof command. 

−feedback filename
Produces a file with information that the compiler system can use to decide which parts of the program will benefit most from global optimization and which parts will benefit most from in-line procedure substitution (requires basic-block counting). (Use this flag only with the −pixie flag.) 

−heavyReports the most heavily used lines in descending order of use.  (Use this flag only with the −pixie flag.) 

−incobj object_file_name
Causes the profile for the named shared library to be printed, in addition to the profile for the executable. You can use this flag multiple times in a single prof command. 

−invocations
For each procedure, reports how many times the procedure was invoked from each of its possible callers (requires basic-block counting).  For this listing, the −exclude and −only options apply to callees, but not to callers.  (Use this flag only with the −pixie flag.) 

−LdirChanges the library directory search order for shared object libraries so that prof looks for them in dir before the library recorded in profile_file and the default library directories.  You can specify multiple −Ldir switches to specify several directory names. 

−LChanges the library directory search order for shared object libraries so that prof never looks for them in the default library directories.  Use this option when the default library directories should not be searched and only the directories specified by −Ldir are to be searched. 

−linesGives the lines in order of occurrence within procedures.  The procedures are sorted in descending order of use.  (Use this flag only with the −pixie flag.) 

−merge filename
Sums the sampling data files (or, in pixie mode, the .Counts files) and writes the result into a new file with the specified name.  The −only and −exclude options have no affect on the merged data. 

−nocounts
Uses 1 for each basic block count. (Use this flag only with the −pixstats or −pixie flag.) 

-numbers
Prints each procedure’s starting line number if source file information is available from the object file.

−only procedure_name
If you use one or more −only options, the profile listing includes only the named procedures, rather than the entire program.  If any option uses an uppercase "O" for "Only," prof uses only the named procedures, rather than the entire program, as the base upon which it calculates percentages. 

−pixieSelects pixie mode, as opposed to sampling mode. 

−pixstats
Selects generation of an alternative pixie-mode report for basic-block profiling data, as previously produced by the pixstats(1) command.  All flags of the previous version of pixstats are recognized, for compatibility. 

−procedures
Reports time spent per procedure (using data obtained from sampling or basic-block counting; the listing tells which one). For basic-block counting, this option also reports the number of invocations per procedure.

−quit nTruncates the −procedures and −heavy listings.  It can truncate after n lines (if n is an integer), after the first entry that represents less than n percent of the total (if n is followed immediately by a "%" character), or after enough entries have been printed to account for n percent of the total (if n is followed immediately by "cum%").  For example, "−quit 15" truncates each part of the listing after 15 lines of text, "−quit 15%" truncates each part after the first line that represents less than 15 percent of the whole, and "−quit 15cum%" truncates each part after the line that brought the cumulative percentage above 15 percent. 

−testcoverage
Reports all lines that never executed (requires basic-block counting). (Use this flag only with the −pixie flag.) 

−totalsFor −procedures and −invocations listings, prints cumulative statistics for the entire object file instead of for each procedure in the object. 

−truecycles [0,1,2]
Generates more analysis of a program to provide a more accurate reading of cycles. The higher the number chosen from the arguments, the more accurate the reading, although the profiler will run slower. (Use this flag only with the −pixie flag.) 

−zeroPrints a list of procedures that were never invoked (requires basic-block counting).  (Use this flag only with the −pixie flag.) 

DESCRIPTION

The prof command analyzes one or more data files generated by the compiler’s execution-profiling system and produces a listing.  The prof command can also combine those data files or produce a feedback file that lets the optimizer take into account the program’s run-time behavior during a subsequent compilation.  Profiling is a three-step process:

     1.Compile the program

     2.Execute the program

     3.Run prof to analyze the data. 

The compiler system provides two kinds of profiling:

PC-sampling
Interrupts the program periodically, recording the value of the program counter.

Basic-block counting
Divides the program into blocks delimited by labels, jump instructions, and branch instructions. It counts the number of times each block executes. This provides more detailed (line by line) information than PC-sampling.

The uprofile and kprofile tools provide a third kind of profiling, performance counter sampling. The Alpha architecture on-chip performance counters are used in performance counter sampling. 

The following sections describe how to perform the various kinds of profiling. 

PC-Sampling Profiles

To use PC-sampling, compile your program with the −p flag (strictly speaking, it is sufficient to use this flag only when linking the program).  Then, run the program containing the profiling startup routine that calls monstartup to allocate extra memory to hold the profiling data. If the program terminates normally or calls exit(2), it records the data in a file at the end of execution. 

If your program uses shared libraries, note that only its call-shared portion is profiled in detail. Only the total time spent in each shared library is recorded. To individually profile all library routines a program uses, build the program with the −non_shared switch (by default, the compiler produces a call-shared object unless −non_shared is explicitly specified), or set the PROFFLAGS environment variable as described in the Environment Variables section. 

After running your program, use prof to analyze the PC-sampling data file.  For example:

cc -c myprog.c
cc -p -o myprog myprog.o
myprog   (generates mon.out)
prof myprog mon.out

When you use prof for PC-sampling, the program name defaults to a.out.  The PC-sampling data file name defaults to mon.out; if you specify more than one PC-sampling data file, prof reports the sum of the data. 

PC-Sampling Environment Variables

You can use environment variables to change the default PC sampling and profile data collection behavior.  The variables are PROFDIR and PROFFLAGS. The general form for setting these variables is:

−For C shell:  setenv varname "value"

−For Bourne shell: varname = "value"; export varname

−For Korn shell: export varname = value

In the preceding example, varname can be one of the following:

PROFDIR
This environment variable causes PC-sampling data files to be generated with unique file names in a specified directory. You specify a directory path as the value and your prof results are placed in the file path/pid.progname where path is the pathname, pid is the process ID of the executing program, and progname is the program name. 

PROFFLAGS
This environment variable can take any of the following values:

−threads
Causes a separate data file to be generated for each thread. The name of the data file takes the following form: pid.sid.progname.  The form of the filename resolves to pid as the process ID of the program, sid as the sequence number of the thread, and progname as the name of the program being profiled. 

−all
Causes the program to fully profile all the permanently loaded shared libraries, in addition to the nonshared or call-shared executable.

−incobj name
Causes the program to profile only the named executable or shared library.

−excobj name
Causes the program not to profile the named executable or shared library.

−stride
Causes prof to change the ratio of text segment stride size to PC-sample counter buffer size, that is, the number of instructions that are counted together in a single counter word.  The appropriate ratio involves a tradeoff of size versus precision.  Strides of 1, 2, 4, and 8 are supported.  A special stride of 0 causes a single PC-sample count to be recorded for each text segment.  The default stride is 2 for the executable, and 0 for each of its shared libraries. If −all or −incobj are specified, all selected objects are profiled with the same stride. 

You can use the PROFDIR and PROFFLAGS environment variables together. For more information, see the Programmer’s Guide. 

Basic-Block Counting

To use basic-block counting, compile your program without the option −p. Use the pixie program to translate your program into a profiling version and generate a file (program_name.Addrs) containing block addresses.  This file contains block addresses.  Then, run the pixie version of the program, which (assuming the program terminates normally or calls exit(2)) will generate a file (program_name.Counts) containing block counts. 

After running the pixie version of your program, use prof with the −pixie flag to analyze the .Addrsand .Counts files.  Notice that you must specify the name of your original program, not the name of the .pixie version. For example:

cc -c myprog.c
cc -o myprog myprog.o
pixie myprog (generates myprog.Addrs and myprog.pixie)
myprog.pixie (generates myprog.Counts)
prof -pixie myprog myprog.Addrs myprog.Counts

When you use prof with the −pixie option, the .Addrs file name defaults to program_name.Addrs, and the .Counts file name defaults to program_name.Counts. If you specify more than one .Counts file, prof reports the sum of the data. 

For each shared library selected for profiling, the prof command searches for an .Addrs file in the following locations if the file location is not explicitly specified on the command line:

−Current directory

−Directory in which the object file is located if the location of the object file is explicitly specified on the command line

−Directory in which pixie created it, as recorded in the .Counts file

For each selected shared library, the prof command searches for an object file in the following locations:

−Directories specified in −Ldir flags

−Directory in which pixie found it, as recorded in the .Addrs file, if the −L flag is specified

−Standard library search directories, as searched by ld, if the −L flag is not specified

Basic-Block Statistics

Use the −pixstats option to get an alternative profile. 

If a disassembly is requested, all basic blocks (or those whose execution count exceeds the −dislimit percentage of total instructions) are disassembled, in increasing address order.  Each block is labeled with its procedure name and any offset from the start of the procedure.  For each instruction, the relative estimated CPU cycle at which the instruction executes is printed, plus its source line, address, binary code, and assembly language.  The total CPU cycles used by one execution of the block, the number of times it was executed, and its percentage of all instructions executed are printed at the end of the block, following any line reporting a non-zero delay caused to a follow-on block. 

The main report begins with a record of the command line.  This is followed by a summary of the program’s behavior:

−Total CPU cycles used by the profiled objects, plus the equivalent number of seconds

−Total number of instructions executed

−Total delay caused by instructions executed in the preceding basic block

−Total integer and floating-point no-op, arithmetic and logical, logical, shift, load, store, load and store, load followed by load, load and store and fetch (data bus use), load and store relative to the stack or global pointers, floating-point, floating-point compare, conditional branch instructions executed (itemized)

−Total number of branch instructions executed whose target instruction is another branch

−Total number of such branches that are estimated to be taken, rather than executing the next instruction in line

−Total basic blocks, procedure calls, and branches that skip a single instruction that were executed. 

Next, some ratios are printed:

−Stores : stores + loads

−Instructions : basic block

−Instructions : branches

−Backward branches : branches

−CPU cycles : procedure calls

−Instructions : procedure calls

−Integer no-ops : integer and floating-point no-ops

−Floating-point no-ops : integer and floating-point no-ops

−Floating-point pipeline interlocks : floating-point operators

Next, basic blocks are analyzed according to how many instructions they contain. For each size, pixstats reports the execution count, its precentage and cumulative percentage relative to both instructions and basic blocks, the number of instructions contained in blocks of that size, the percentage and cumulative percentage of this relative to all instructions, and the CPU-cycle cost per instruction of blocks of that size. Then, pixstats prints various averages and quartiles of basic block size, plus the largest basic block execution count encountered (to indicate the chance of integer overflow in the analysis). 

Next, pixstats analyzes the number of registers (integer and floating-point) that are saved on procedure entry (and restored on exit). It prints the number of procedure entries that save a given number of registers, and the percentage and cumulative percentage of this relative to all procedure entries, all registers saved, and all instructions executed. Finally, it prints some averages and ratios. 

The next two tables contain information on the sizes of executed procedures’ stack frames and the frequency of execution of each kind of instruction.  Frame sizes are reported in “bits” for example, 6 bits means a 32- to 48-byte stack frame. The number, percentage, and cumulative percentage of executed calls to procedures with the given frame size is printed. Similarly, the execution count is printed for each machine instruction code, but this table is ordered by decreasing usage. 

The next four tables are similar. They contain information on the memory displacement from a base register, in each of four kinds of instruction:

−Branch

−Load or store within a stack frame

−Load or store within a global offset table

−All load or store instructions

Again, the “size” of the displacement is reported in bits; for example, 6 bits means a 32 to 63 byte displacement. For both positive displacements (in the “0-extend” column) and negative displacements (in the “1-extend” column), the execution count is printed along with percentage and cumulative percentage.  The summed cumulative percentage is printed last (in the “sign-extend” column). 

In the “static” analysis of instructions, each instruction is counted once per executed basic-block. The “static” distribution will be the same as the regular opcode distribution when -nocounts is specified. Following “static” totals for instructions and basic blocks, the number and percentage of each instruction code is listed. 

The next two tables contain information on how many times each integer and floating-point register was accessed, plus its percentage, ordered by register number.  For integer registers, the number and percent of uses as a base register in memory operations is also listed. 

Finally, pixstats prints a flat profile of CPU cycles used by procedures.  This includes the CPU cycles used by the procedure, the percentage of the total, the cumulative percentage, the number of instructions executed as part of the procedure, its average number of CPU cycles per instruction, the number of calls made to the procedure, the average number of CPU cycles per call, and the procedure name. If −numbers is specified, the object and source file names and line number are also printed. 

Performance Counter Samples

After running the uprofile or kprofile utility to collect profiling data or your program or the kernel, respectively, run prof to examine the resulting mon.out or kmon.out file, as follows:

−For uprofile output: prof prog_name mon.out

−For kprofile output: prof /vmunix kmon.out

Use prof as for PC sampling, except that only the executable has a profile.  Old performance counter sample data files, generated on versions of the operating system prior to Digital UNIX Version 4.0, must be analyzed as if they contained PC-sampling data. 

FILES

crt0.oNormal startup code

mcrt0.oStartup code for PC-sampling

libprof1.aLibrary for PC-sampling

kmon.outDefault kprofile data file

mon.outDefault PC-sampling data file

umon.outDefault uprofile data file

RELATED INFORMATION

Programmer’s Guide

Commands:  as(1), atom(1), cc(1), gprof(1), uprofile(1), kprofile(1), dxprof(1).  (dxprof(1) is available only if the Developer’s Tool Kit and associated reference pages are installed on your system.) 

Atom Tools: pixie(5)

Functions: monitor(3), profil(2)