The Metering System is a portable Common Lisp code profiling tool. It gathers timing and consing statistics for specified functions while a program is running.

The Metering System

The Metering System is a portable Common Lisp code profiling tool. It gathers timing and consing statistics for specified functions while a program is running.

The Metering System is a combination of

  • the Monitor package written by Chris McConnell
  • the Profile package written by Skef Wholey and Rob MacLachlan

The two systems were merged and extended by Mark Kantrowitz.

Metering System was refreshed and adapted to the 2016 realities by Daniel Kochmański.

This code is in the public domain and is distributed without warranty of any kind.

Bug reports, comments, and suggestions should be sent to

Change Log

Date Name Ver Notes
26-JUN-90 mk Merged functionality of Monitor and Profile packages.
26-JUN-90 mk Now handles both inclusive and exclusive statistics with respect to nested calls. (Allows it to subtract total monitoring overhead for each function, not just the time spent monitoring the function itself.)
26-JUN-90 mk The table is now saved so that one may manipulate the data (sorting it, etc.) even after the original source of the data has been cleared.
25-SEP-90 mk Added get-cons functions for Lucid 3.0, MACL 1.3.2 required-arguments functions for Lucid 3.0, Franz Allegro CL, and MACL 1.3.2.
25-JAN-91 mk Now uses fdefinition if available.
25-JAN-91 mk Replaced (and :allegro (not :coral)) with :excl. Much better solution for the fact that both call themselves :allegro.
5-JUL-91 mk Fixed warning to occur only when file is loaded uncompiled.
5-JUL-91 mk When many unmonitored functions, print out number instead of whole list.
24-MAR-92 mk Updated for CLtL2 compatibility. space measuring doesn’t work in MCL, but fixed so that timing statistics do.
26-MAR-92 mk Updated for Lispworks. Replaced :ccl with (and :ccl (not :lispworks)).
27-MAR-92 mk Added get-cons for Allegro-V4.0.
01-JAN-93 mk 2.0 Support for MCL 2.0, CMU CL 16d, Allegro V3.1/4.0/4.1, Lucid 4.0, ibcl
25-JAN-94 mk 2.1 Patches for CLISP from Bruno Haible.
26-FEB-16 dk 3.0 General clean-up - removal of the obsolete implementations support and constructs, testing on the active implementations etc.
26-FEB-16 dk 3.1 Make warnings more ASDF-friendly
25-MAY-16 dk 3.2 Improve the documentation (document ignore-no-calls parameter)

To Do

  • Speed up monitoring code. Replace use of hash tables with an embedded offset in an array so that it will be faster than using gethash. (i.e., svref/closure reference is usually faster than gethash).
  • Check robustness with respect to profiled functions.
  • Add option to record caller statistics – this would list who called which functions and how often.
  • Switches to turn timing/CONSING statistics collection on/off.
  • Additional tests.


METERING has been tested (successfully) in the following lisps:

Name Version Testing date Addional notes
ABCL 1.3.3 Feb 2016
CCL 1.11 Feb 2016
CMUCL 21a Feb 2016
CLISP 2.49 Feb 2016
ECL 16.1.2 Feb 2016
GCL 2.6.13-pre Feb 2016
SBCL 1.3.2 Feb 2016
XCL Feb 2016 unstable (random crashes)

METERING needs to be tested in the following lisps:

  • Allegro
  • LispWorks
  • mocl

On XCL and GCL loading system with ASDF won’t work.

GCL has to first load the file, then compile it and load the compiled before:

(load "") ; GCL's issue
(compile-file "")
(load *)

METERING may be load with ASDF or by compiling and loading file:

(load (compile-file ""))

(load "metering.asd")
(asdf:load-system 'metering)


This system runs in any valid Common Lisp. Two small implementation-dependent changes can be made to improve performance and prettiness. In the section labelled “Implementation Dependent Changes” below, you should tailor the functions REQUIRED-ARGUMENTS, GET-CONS to your implementation for the best results. If GET-CONS is not specified for your implementation, no consing information will be reported. If you tailor these functions for a particular version of Common Lisp, we’d appreciate receiving the code.

Usage Notes


Start by monitoring big pieces of the program, then carefully choose which functions close to, but not in, the inner loop are to be monitored next. Don’t monitor functions that are called by other monitored functions: you will only confuse yourself.

If the per-call time reported is less than 1/10th of a second, then consider the clock resolution and profiling overhead before you believe the time. It may be that you will need to run your program many times in order to average out to a higher resolution.

The easiest way to use this package is to load it and execute either

(mon:with-monitoring (names*) ()


(mon:monitor-form your-form)

The former allows you to specify which functions will be monitored; the latter monitors all functions in the current package. Both automatically produce a table of statistics. Other variants can be constructed from the monitoring primitives, which are described below, along with a fuller description of these two macros.

For best results, compile this file before using.


Unless you are very lucky, the length of your machine’s clock “tick” is probably much longer than the time it takes a simple function to run. For example, on the IBM RT, the clock resolution is 1/50th of a second. This means that if a function is only called a few times, then only the first couple of decimal places are really meaningful.


The added monitoring code takes time to run every time that the monitored function is called, which can disrupt the attempt to collect timing information. In order to avoid serious inflation of the times for functions that take little time to run, an estimate of the overhead due to monitoring is subtracted from the times reported for each function.

Although this correction works fairly well, it is not totally accurate, resulting in times that become increasingly meaningless for functions with short runtimes. For example, subtracting the estimated overhead may result in negative times for some functions. This is only a concern when the estimated profiling overhead is many times larger than reported total CPU time.

If you monitor functions that are called by monitored functions, in :inclusive mode the monitoring overhead for the inner function is subtracted from the CPU time for the outer function. [We do this by counting for each function not only the number of calls to this function, but also the number of monitored calls while it was running.] In :exclusive mode this is not necessary, since we subtract the monitoring time of inner functions, overhead & all.

Otherwise, the estimated monitoring overhead is not represented in the reported total CPU time. The sum of total CPU time and the estimated monitoring overhead should be close to the total CPU time for the entire monitoring run (as determined by TIME).

A timing overhead factor is computed at load time. This will be incorrect if the monitoring code is run in a different environment than this file was loaded in. For example, saving a core image on a high performance machine and running it on a low performance one will result in the use of an erroneously small overhead factor.

If your times vary widely, possible causes are:

  • Garbage collection. Try turning it off, then running your code. Be warned that monitoring code will probably cons when it does (get-internal-run-time).


WITH-MONITORING (&rest functions)                         [Macro]
                (&optional (nested :exclusive) 
                           (threshold 0.01)
                           (key :percent-time))
                &body body
The named functions will be set up for monitoring, the body forms executed,
a table of results printed, and the functions unmonitored. The nested,
threshold, and key arguments are passed to report-monitoring below.

MONITOR-FORM form                                         [Macro]
              &optional (nested :exclusive)
                        (threshold 0.01)
                        (key :percent-time)
All functions in the current package are set up for monitoring while
the form is executed, and automatically unmonitored after a table of
results has been printed. The nested, threshold, and key arguments 
are passed to report-monitoring below.

*MONITORED-FUNCTIONS*                                     [Variable]
This holds a list of all functions that are currently being monitored.

MONITOR &rest names                                       [Macro]
The named functions will be set up for monitoring by augmenting
their function definitions with code that gathers statistical information
about code performance. As with the TRACE macro, the function names are
not evaluated. Calls the function MON::MONITORING-ENCAPSULATE on each
function name. If no names are specified, returns a list of all 
monitored functions.

If name is not a symbol, it is evaled to return the appropriate
closure. This allows you to monitor closures stored anywhere like
in a variable, array or structure. Most other monitoring packages 
can't handle this. 

MONITOR-ALL &optional (package *package*)                 [Function]
Monitors all functions in the specified package, which defaults to
the current package.

UNMONITOR &rest names                                     [Macro]
Removes monitoring code from the named functions. If no names are
specified, all currently monitored functions are unmonitored.

RESET-MONITORING-INFO name                                [Function]
Resets the monitoring statistics for the specified function.

RESET-ALL-MONITORING                                      [Function]
Resets the monitoring statistics for all monitored functions.

MONITORED name                                            [Function]
Predicate to test whether a function is monitored.

REPORT-MONITORING &optional names                         [Function]
                            (nested :exclusive) 
                            (threshold 0.01)
                            (key :percent-time)
Creates a table of monitoring information for the specified list
of names, and displays the table using display-monitoring-results.
If names is :all or nil, uses all currently monitored functions.
Takes the following arguments:
   - NESTED specifies whether nested calls of monitored functions
     are included in the times for monitored functions.
     o  If :inclusive, the per-function information is for the entire
        duration of the monitored function, including any calls to
        other monitored functions. If functions A and B are monitored,
        and A calls B, then the accumulated time and consing for A will
        include the time and consing of B.  Note: if a function calls
        itself recursively, the time spent in the inner call(s) may
        be counted several times.
     o  If :exclusive, the information excludes time attributed to
        calls to other monitored functions. This is the default.
   - THRESHOLD specifies that only functions which have been executed
     more than threshold percent of the time will be reported. Defaults
     to 1%. If a threshold of 0 is specified, all functions are listed,
     even those with 0 or negative running times (see note on overhead).
   - KEY specifies that the table be sorted by one of the following
     sort keys:
        :function       alphabetically by function name
        :percent-time   by percent of total execution time
        :percent-cons   by percent of total consing
        :calls          by number of times the function was called
        :time-per-call  by average execution time per function
        :cons-per-call  by average consing per function
        :time           same as :percent-time
        :cons           same as :percent-cons
   - IGNORE-NO-CALLS specifies whenever functions which were not
     called should be reported.

DISPLAY-MONITORING-RESULTS &optional (threshold 0.01)     [Function]
                                     (key :percent-time)
                                     (ignore-no-calls t)
Prints a table showing for each named function:
   - the total CPU time used in that function for all calls
   - the total number of bytes consed in that function for all calls
   - the total number of calls
   - the average amount of CPU time per call
   - the average amount of consing per call
   - the percent of total execution time spent executing that function
   - the percent of total consing spent consing in that function
Summary totals of the CPU time, consing, and calls columns are printed.
An estimate of the monitoring overhead is also printed. May be run
even after unmonitoring all the functions, to play with the data.


                   %     %                       Per      Total   Total
  Function         Time  Cons  Calls  Sec/Call   Call     Time    Cons
  FIND-ROLE:       0.58  0.00    136  0.003521      0  0.478863       0
  GROUP-ROLE:      0.35  0.00    365  0.000802      0  0.292760       0
  GROUP-PROJECTOR: 0.05  0.00    102  0.000408      0  0.041648       0
  FEATURE-P:       0.02  0.00    570  0.000028      0  0.015680       0
  TOTAL:                        1173                   0.828950       0
  Estimated total monitoring overhead: 0.88 seconds