Repository: cyrus-and/prof
Branch: master
Commit: aba0aa7a9a2c
Files: 4
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Directory structure:
gitextract_sxopiv_i/

├── .gitignore
├── README.md
├── make-readme.sh
└── prof.h

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FILE: README.md
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# Prof

Self-contained C/C++ profiler library for Linux.

Prof offers a quick way to measure performance events (CPU clock cycles,
cache misses, branch mispredictions, etc.) of C/C++ code snippets. Prof is
just a wrapper around the `perf_event_open` system call, its main goal is to
be easy to setup and painless to use for targeted optimizations, namely, when
the hot spot has already been identified. In no way Prof is a replacement for
a fully-fledged profiler like perf, gprof, callgrind, etc.

## Examples

### Minimal

The following snippet prints the rough number of CPU clock cycles spent in
executing the code between the two Prof calls:

```c
#include "prof.h"

int main()
{
    PROF_START();
    // slow code goes here...
    PROF_STDOUT();
}
```

### Custom options

The following snippet instead counts both read and write faults of the level
1 data cache that occur in the userland code between the two Prof calls:

```c
#include <stdio.h>

#define PROF_USER_EVENTS_ONLY
#define PROF_EVENT_LIST \
    PROF_EVENT_CACHE(L1D, READ, MISS) \
    PROF_EVENT_CACHE(L1D, WRITE, MISS)
#include "prof.h"

int main()
{
    uint64_t faults[2] = { 0 };

    PROF_START();
    // slow code goes here...
    PROF_DO(faults[index] += counter);

    // fast or uninteresting code goes here...

    PROF_START();
    // slow code goes here...
    PROF_DO(faults[index] += counter);

    printf("L1: R = %" PRIu64 "; W = %" PRIu64 "\faults[0], faults[1]);
}
```

## Installation

Just include `prof.h`. Here is a quick way to fetch the latest version:

    wget -q https://raw.githubusercontent.com/cyrus-and/prof/master/prof.h

Please be aware that Prof uses `__attribute__((constructor))` to be the more
straightforward to setup as possible, so the header cannot be included more
than once.

This also means that in order to use Prof from additional threads, the setup
code (`prof_init` and `prof_fini` calls) must be replicated for each one of
them, for example:

```c
void *thread(void *args) {
    prof_init();

    // ...

    prof_fini();
    return NULL;
}
```

## Setup

Since Prof uses `perf_event_open` make sure to have the permission to access
the performance counters: either run the program as superuser (discouraged)
or set the value of `perf_event_paranoid` appropriately, for example:

```console
$ echo 1 | sudo tee /proc/sys/kernel/perf_event_paranoid
```

Optionally make it permanent with:

```console
$ echo 'kernel.perf_event_paranoid=1' | sudo tee /etc/sysctl.d/local.conf
```

See `man perf_event_open` for more information.

## API

### PROF_START()

Reset the counters and (re)start counting the events.

The events to be monitored are specified by setting the `PROF_EVENT_LIST`
macro before including this file to a list of `PROF_EVENT_*` invocations;
defaults to counting the number CPU clock cycles.

If the `PROF_USER_EVENTS_ONLY` macro is defined before including this file
then kernel and hypervisor events are excluded from the count.

### PROF_EVENT(type, config)

Specify an event to be monitored, `type` and `config` are defined in the
documentation of the `perf_event_open` system call.

### PROF_EVENT_HW(config)

Same as `PROF_EVENT` but for hardware events; prefix `PERF_COUNT_HW_` must be
omitted from `config`.

### PROF_EVENT_SW(config)

Same as `PROF_EVENT` but for software events; prefix `PERF_COUNT_SW_` must be
omitted from `config`.

### PROF_EVENT_CACHE(cache, op, result)

Same as `PROF_EVENT` but for cache events; prefixes `PERF_COUNT_HW_CACHE_`,
`PERF_COUNT_HW_CACHE_OP_` and `PERF_COUNT_HW_CACHE_RESULT_` must be omitted
from `cache`, `op` and `result`, respectively. Again `cache`, `op` and
`result` are defined in the documentation of the `perf_event_open` system
call.

### PROF_STOP()

Stop counting the events. The counter array can then be accessed with
`PROF_COUNTERS`.

### PROF_COUNTERS

Access the counter array. The order of counters is the same of the events
defined in `PROF_EVENT_LIST`. Elements of this array are 64 bit unsigned
integers.

### PROF_DO(block)

Stop counting the events and execute the code provided by `block` for each
event. Within `code`: `index` refers to the event position index in the
counter array defined by `PROF_COUNTERS`; `counter` is the actual value of
the counter. `index` is a 64 bit unsigned integer.

### PROF_CALL(callback)

Same as `PROF_DO` except that `callback` is the name of a *callable* object
(e.g. a function) which, for each event, is be called with the two parameters
`index` and `counter`.

### PROF_FILE(file)

Stop counting the events and write to `file` (a stdio.h `FILE *`) as many
lines as are events in `PROF_EVENT_LIST`. Each line contains `index` and
`counter` (as defined by `PROF_DO`) separated by a tabulation character. If
there is only one event then `index` is omitted.

### PROF_STDOUT()

Same as `PROF_LOG_FILE` except that `file` is `stdout`.

### PROF_STDERR()

Same as `PROF_LOG_FILE` except that `file` is `stderr`.

## License

Copyright (c) 2024 Andrea Cardaci <cyrus.and@gmail.com>

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

<!-- autogenerated from prof.h -->


================================================
FILE: make-readme.sh
================================================
#!/bin/sh

<prof.h >README.md awk '
BEGIN                  { first_doc = 1 }
/^ \*\/$/              { def = NR + 1; in_doc = 0 }
in_doc                 { sub(" \\* ?", ""); doc=(doc == "" ? $0 : doc "\n" $0) }
/^\/\*$/               { in_doc = 1 }
NR==def                { if (first_doc) first_doc = 0; else print "" }
NR==def && /^#define/  { NF -= 1; $1 = "###"; printf "%s\n\n%s", $0, doc; doc="" }
NR==def && !/^#define/ { print doc; doc = "" }
END                    { printf "\n%s\n\n<!-- autogenerated from prof.h -->\n", doc }
'


================================================
FILE: prof.h
================================================
/*
 * # Prof
 *
 * Self-contained C/C++ profiler library for Linux.
 *
 * Prof offers a quick way to measure performance events (CPU clock cycles,
 * cache misses, branch mispredictions, etc.) of C/C++ code snippets. Prof is
 * just a wrapper around the `perf_event_open` system call, its main goal is to
 * be easy to setup and painless to use for targeted optimizations, namely, when
 * the hot spot has already been identified. In no way Prof is a replacement for
 * a fully-fledged profiler like perf, gprof, callgrind, etc.
 *
 * ## Examples
 *
 * ### Minimal
 *
 * The following snippet prints the rough number of CPU clock cycles spent in
 * executing the code between the two Prof calls:
 *
 * ```c
 * #include "prof.h"
 *
 * int main()
 * {
 *     PROF_START();
 *     // slow code goes here...
 *     PROF_STDOUT();
 * }
 * ```
 *
 * ### Custom options
 *
 * The following snippet instead counts both read and write faults of the level
 * 1 data cache that occur in the userland code between the two Prof calls:
 *
 * ```c
 * #include <stdio.h>
 *
 * #define PROF_USER_EVENTS_ONLY
 * #define PROF_EVENT_LIST \
 *     PROF_EVENT_CACHE(L1D, READ, MISS) \
 *     PROF_EVENT_CACHE(L1D, WRITE, MISS)
 * #include "prof.h"
 *
 * int main()
 * {
 *     uint64_t faults[2] = { 0 };
 *
 *     PROF_START();
 *     // slow code goes here...
 *     PROF_DO(faults[index] += counter);
 *
 *     // fast or uninteresting code goes here...
 *
 *     PROF_START();
 *     // slow code goes here...
 *     PROF_DO(faults[index] += counter);
 *
 *     printf("L1: R = %" PRIu64 "; W = %" PRIu64 "\faults[0], faults[1]);
 * }
 * ```
 *
 * ## Installation
 *
 * Just include `prof.h`. Here is a quick way to fetch the latest version:
 *
 *     wget -q https://raw.githubusercontent.com/cyrus-and/prof/master/prof.h
 *
 * Please be aware that Prof uses `__attribute__((constructor))` to be the more
 * straightforward to setup as possible, so the header cannot be included more
 * than once.
 *
 * This also means that in order to use Prof from additional threads, the setup
 * code (`prof_init` and `prof_fini` calls) must be replicated for each one of
 * them, for example:
 *
 * ```c
 * void *thread(void *args) {
 *     prof_init();
 *
 *     // ...
 *
 *     prof_fini();
 *     return NULL;
 * }
 * ```
 *
 * ## Setup
 *
 * Since Prof uses `perf_event_open` make sure to have the permission to access
 * the performance counters: either run the program as superuser (discouraged)
 * or set the value of `perf_event_paranoid` appropriately, for example:
 *
 * ```console
 * $ echo 1 | sudo tee /proc/sys/kernel/perf_event_paranoid
 * ```
 *
 * Optionally make it permanent with:
 *
 * ```console
 * $ echo 'kernel.perf_event_paranoid=1' | sudo tee /etc/sysctl.d/local.conf
 * ```
 *
 * See `man perf_event_open` for more information.
 */
#ifndef PROF_H
#define PROF_H

#include <errno.h>
#include <inttypes.h>
#include <linux/perf_event.h>
#include <stdarg.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/syscall.h>
#include <unistd.h>

/*
 * ## API
 */

/*
 * Reset the counters and (re)start counting the events.
 *
 * The events to be monitored are specified by setting the `PROF_EVENT_LIST`
 * macro before including this file to a list of `PROF_EVENT_*` invocations;
 * defaults to counting the number CPU clock cycles.
 *
 * If the `PROF_USER_EVENTS_ONLY` macro is defined before including this file
 * then kernel and hypervisor events are excluded from the count.
 */
#define PROF_START()                                                           \
    do {                                                                       \
        PROF_IOCTL_(ENABLE);                                                   \
        PROF_IOCTL_(RESET);                                                    \
    } while (0)

/*
 * Specify an event to be monitored, `type` and `config` are defined in the
 * documentation of the `perf_event_open` system call.
 */
#define PROF_EVENT(type, config)                                               \
    (uint32_t)(type), (uint64_t)(config),

/*
 * Same as `PROF_EVENT` but for hardware events; prefix `PERF_COUNT_HW_` must be
 * omitted from `config`.
 */
#define PROF_EVENT_HW(config)                                                  \
    PROF_EVENT(PERF_TYPE_HARDWARE, PERF_COUNT_HW_ ## config)

/*
 * Same as `PROF_EVENT` but for software events; prefix `PERF_COUNT_SW_` must be
 * omitted from `config`.
 */
#define PROF_EVENT_SW(config)                                                  \
    PROF_EVENT(PERF_TYPE_SOFTWARE, PERF_COUNT_SW_ ## config)

/*
 * Same as `PROF_EVENT` but for cache events; prefixes `PERF_COUNT_HW_CACHE_`,
 * `PERF_COUNT_HW_CACHE_OP_` and `PERF_COUNT_HW_CACHE_RESULT_` must be omitted
 * from `cache`, `op` and `result`, respectively. Again `cache`, `op` and
 * `result` are defined in the documentation of the `perf_event_open` system
 * call.
 */
#define PROF_EVENT_CACHE(cache, op, result)                                    \
    PROF_EVENT(PERF_TYPE_HW_CACHE,                                             \
               (PERF_COUNT_HW_CACHE_ ## cache) |                               \
               (PERF_COUNT_HW_CACHE_OP_ ## op << 8) |                          \
               (PERF_COUNT_HW_CACHE_RESULT_ ## result << 16))

/*
 * Stop counting the events. The counter array can then be accessed with
 * `PROF_COUNTERS`.
 */
#define PROF_STOP()                                                            \
    do {                                                                       \
        PROF_IOCTL_(DISABLE);                                                  \
        PROF_READ_COUNTERS_(prof_event_buf_);                                  \
    } while (0)

/*
 * Access the counter array. The order of counters is the same of the events
 * defined in `PROF_EVENT_LIST`. Elements of this array are 64 bit unsigned
 * integers.
 */
#define PROF_COUNTERS                                                          \
    (prof_event_buf_ + 1)

/*
 * Stop counting the events and execute the code provided by `block` for each
 * event. Within `code`: `index` refers to the event position index in the
 * counter array defined by `PROF_COUNTERS`; `counter` is the actual value of
 * the counter. `index` is a 64 bit unsigned integer.
 */
#define PROF_DO(block)                                                         \
    do {                                                                       \
        uint64_t i_;                                                           \
        PROF_STOP();                                                           \
        for (i_ = 0; i_ < prof_event_cnt_; i_++) {                             \
            uint64_t index = i_;                                               \
            uint64_t counter = prof_event_buf_[i_ + 1];                        \
            (void)index;                                                       \
            (void)counter;                                                     \
            block;                                                             \
        }                                                                      \
    } while (0)

/*
 * Same as `PROF_DO` except that `callback` is the name of a *callable* object
 * (e.g. a function) which, for each event, is be called with the two parameters
 * `index` and `counter`.
 */
#define PROF_CALL(callback)                                                    \
    PROF_DO(callback(index, counter))

/*
 * Stop counting the events and write to `file` (a stdio.h `FILE *`) as many
 * lines as are events in `PROF_EVENT_LIST`. Each line contains `index` and
 * `counter` (as defined by `PROF_DO`) separated by a tabulation character. If
 * there is only one event then `index` is omitted.
 */
#define PROF_FILE(file)                                                        \
    PROF_DO(if (prof_event_cnt_ > 1) {                                         \
            fprintf((file), "%" PRIu64 "\t%" PRIu64 "\n", index, counter);     \
        } else {                                                               \
            fprintf((file), "%" PRIu64 "\n", counter);                         \
        }                                                                      \
    )

/*
 * Same as `PROF_LOG_FILE` except that `file` is `stdout`.
 */
#define PROF_STDOUT()                                                          \
    PROF_FILE(stdout)

/*
 * Same as `PROF_LOG_FILE` except that `file` is `stderr`.
 */
#define PROF_STDERR()                                                          \
    PROF_FILE(stderr)

/* DEFAULTS ----------------------------------------------------------------- */

#ifndef PROF_EVENT_LIST
#ifdef PERF_COUNT_HW_REF_CPU_CYCLES /* since Linux 3.3 */
#define PROF_EVENT_LIST PROF_EVENT_HW(REF_CPU_CYCLES)
#else
#define PROF_EVENT_LIST PROF_EVENT_HW(CPU_CYCLES)
#endif
#endif

/* UTILITY ------------------------------------------------------------------ */

#define PROF_ASSERT_(x)                                                        \
    do {                                                                       \
        if (!(x)) {                                                            \
            fprintf(stderr, "# %s:%d: PROF error", __FILE__, __LINE__);        \
            if (errno) {                                                       \
                fprintf(stderr, " (%s)", strerror(errno));                     \
            }                                                                  \
            printf("\n");                                                      \
            abort();                                                           \
        }                                                                      \
    } while (0)

#define PROF_IOCTL_(mode)                                                      \
    do {                                                                       \
        PROF_ASSERT_(ioctl(prof_fd_,                                           \
                           PERF_EVENT_IOC_ ## mode,                            \
                           PERF_IOC_FLAG_GROUP) != -1);                        \
    } while (0)

#define PROF_READ_COUNTERS_(buffer)                                            \
    do {                                                                       \
        const ssize_t to_read = sizeof(uint64_t) * (prof_event_cnt_ + 1);      \
        PROF_ASSERT_(read(prof_fd_, buffer, to_read) == to_read);              \
    } while (0)

/* SETUP -------------------------------------------------------------------- */

static __thread int prof_fd_;
static __thread uint64_t prof_event_cnt_;
static __thread uint64_t *prof_event_buf_;

static void prof_init_(uint64_t dummy, ...) {
    uint32_t type;
    va_list ap;

    prof_fd_ = -1;
    prof_event_cnt_ = 0;
    va_start(ap, dummy);
    while (type = va_arg(ap, uint32_t), type != (uint32_t)-1) {
        struct perf_event_attr pe;
        uint64_t config;
        int fd;

        config = va_arg(ap, uint64_t);

        memset(&pe, 0, sizeof(struct perf_event_attr));
        pe.size = sizeof(struct perf_event_attr);
        pe.read_format = PERF_FORMAT_GROUP;
        pe.type = type;
        pe.config = config;
        #ifdef PROF_USER_EVENTS_ONLY
        pe.exclude_kernel = 1;
        pe.exclude_hv = 1;
        #endif

        fd = syscall(__NR_perf_event_open, &pe, 0, -1, prof_fd_, 0);
        PROF_ASSERT_(fd != -1);
        if (prof_fd_ == -1) {
            prof_fd_ = fd;
        }

        prof_event_cnt_++;
    }
    va_end(ap);

    prof_event_buf_ = (uint64_t *)malloc((prof_event_cnt_ + 1) *
                                         sizeof(uint64_t));
}

void __attribute__((constructor)) prof_init()
{
    prof_init_(0, PROF_EVENT_LIST /*,*/ (uint32_t)-1);
}

void __attribute__((destructor)) prof_fini()
{
    PROF_ASSERT_(close(prof_fd_) != -1);
    free(prof_event_buf_);
}

#endif

/*
 * ## License
 *
 * Copyright (c) 2024 Andrea Cardaci <cyrus.and@gmail.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */