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jit.p: Add CPU performance counters as profiler source
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This profiler mode samples based on a specific CPU performance event
(cache-misses, branch-misses, etc) instead of wall-clock time.

Usage example:

  -jp=S[cache-misses]

Implementation by Antonio Nikishaev (@llelf).
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@lukego
lukego committed Sep 14, 2015
1 parent 6d7602c commit 53aedce
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Showing 2 changed files with 192 additions and 15 deletions.
8 changes: 6 additions & 2 deletions lib/luajit/src/jit/p.lua
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Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,7 @@
-- G Produce raw output suitable for graphical tools (e.g. flame graphs).
-- m<number> Minimum sample percentage to be shown. Default: 3.
-- i<number> Sampling interval in milliseconds. Default: 10.
-- S[<string>] Events source if performace events are enabled
--
----------------------------------------------------------------------------

Expand Down Expand Up @@ -243,11 +244,14 @@ end
-- Start profiling.
local function prof_start(mode)
local interval = ""
mode = mode:gsub("i%d*", function(s) interval = s; return "" end)
mode = mode:gsub("i%d+", function(s) interval = s; return "" end)
prof_min = 3
mode = mode:gsub("m(%d+)", function(s) prof_min = tonumber(s); return "" end)
prof_depth = 1
mode = mode:gsub("%-?%d+", function(s) prof_depth = tonumber(s); return "" end)
local flavour = "S[vanilla]"
mode = mode:gsub("S%[.+%]", function(s) flavour = s; return "" end)

local m = {}
for c in mode:gmatch(".") do m[c] = c end
prof_states = m.z or m.v
Expand Down Expand Up @@ -285,7 +289,7 @@ local function prof_start(mode)
prof_count1 = {}
prof_count2 = {}
prof_samples = 0
profile.start(scope:lower()..interval, prof_cb)
profile.start(scope:lower()..interval..flavour, prof_cb)
prof_ud = newproxy(true)
getmetatable(prof_ud).__gc = prof_finish
end
Expand Down
199 changes: 186 additions & 13 deletions lib/luajit/src/lj_profile.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@

#define lj_profile_c
#define LUA_CORE
#define _GNU_SOURCE 1

#include "lj_obj.h"

Expand All @@ -29,6 +30,17 @@
#define profile_lock(ps) UNUSED(ps)
#define profile_unlock(ps) UNUSED(ps)

#if 1
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/syscall.h>
#include <sys/ioctl.h>
#include <linux/perf_event.h>
#include <sys/prctl.h>
#endif


#elif LJ_PROFILE_PTHREAD

#include <pthread.h>
Expand Down Expand Up @@ -62,6 +74,8 @@ typedef struct ProfileState {
SBuf sb; /* String buffer for stack dumps. */
int interval; /* Sample interval in milliseconds. */
int samples; /* Number of samples for next callback. */
char *flavour; /* What generates profiling events. */
int perf_event_fd; /* Performace event file descriptor */
int vmstate; /* VM state when profile timer triggered. */
#if LJ_PROFILE_SIGPROF
struct sigaction oldsa; /* Previous SIGPROF state. */
Expand Down Expand Up @@ -176,29 +190,178 @@ static void profile_signal(int sig)
profile_trigger(&profile_state);
}


static int perf_event_open(struct perf_event_attr *attr,
pid_t pid, int cpu, int group_fd,
unsigned long flags)
{
return syscall(SYS_perf_event_open, attr, pid, cpu, group_fd, flags);
}


static void register_prof_events(ProfileState *ps)
{
struct flavour_t {
char *name; uint32_t type; uint64_t config;
};

static struct flavour_t flavours[] =
{
{ "sw-cpu-clock",
PERF_TYPE_SOFTWARE, PERF_COUNT_SW_CPU_CLOCK },

{ "sw-context-switches",
PERF_TYPE_SOFTWARE, PERF_COUNT_SW_CONTEXT_SWITCHES },

{ "sw-page-faults",
PERF_TYPE_SOFTWARE, PERF_COUNT_SW_PAGE_FAULTS },

{ "sw-minor-page-faults",
PERF_TYPE_SOFTWARE, PERF_COUNT_SW_PAGE_FAULTS_MIN },

{ "sw-major-page-faults",
PERF_TYPE_SOFTWARE, PERF_COUNT_SW_PAGE_FAULTS_MAJ },

{ "branch-instructions",
PERF_TYPE_HARDWARE, PERF_COUNT_HW_BRANCH_INSTRUCTIONS },

{ "cpu-cycles",
PERF_TYPE_HARDWARE, PERF_COUNT_HW_CPU_CYCLES },

{ "instructions",
PERF_TYPE_HARDWARE, PERF_COUNT_HW_INSTRUCTIONS },

{ "cache-references",
PERF_TYPE_HARDWARE, PERF_COUNT_HW_CACHE_REFERENCES },

{ "cache-misses",
PERF_TYPE_HARDWARE, PERF_COUNT_HW_CACHE_MISSES },

{ "branch-instructions",
PERF_TYPE_HARDWARE, PERF_COUNT_HW_BRANCH_INSTRUCTIONS },

{ "branch-misses",
PERF_TYPE_HARDWARE, PERF_COUNT_HW_BRANCH_MISSES },

{ "bus-cycles",
PERF_TYPE_HARDWARE, PERF_COUNT_HW_BUS_CYCLES },

{ "stalled-cycles-frontend",
PERF_TYPE_HARDWARE, PERF_COUNT_HW_STALLED_CYCLES_FRONTEND },

{ "stalled-cycles-backend",
PERF_TYPE_HARDWARE, PERF_COUNT_HW_STALLED_CYCLES_BACKEND },

{ "cpu-cycles",
PERF_TYPE_HARDWARE, PERF_COUNT_HW_REF_CPU_CYCLES },

{ 0, 0, 0 }
};


struct perf_event_attr attr = { };

memset(&attr, 0, sizeof(struct perf_event_attr));

const struct flavour_t *f;
for (f = flavours; f->name != 0; f++)
{
if (strcmp (ps->flavour, f->name) == 0)
{
attr.type = f->type;
attr.config = f->config;
break;
}
}

if (strcmp (ps->flavour, "?") == 0)
{
const struct flavour_t *f;
fprintf (stderr, "I know: ");
for (f = flavours; f->name != 0; f++)
fprintf (stderr, "%s ", f->name);
fprintf(stderr, "\n");
}
else if (! f->name)
{
fprintf (stderr, "unknown profiling flavour `%s', S[?] to list\n", ps->flavour);
}

attr.size = sizeof(struct perf_event_attr);
attr.sample_type = PERF_SAMPLE_IP;
/* attr.read_format = PERF_FORMAT_GROUP | PERF_FORMAT_ID; */
attr.disabled=1;
attr.pinned=1;
attr.exclude_kernel=1;
attr.exclude_hv=1;

attr.sample_period = ps->interval;
/* attr.watermark=0; */
/* attr.wakeup_events=1; */

int fd = perf_event_open(&attr, 0, -1, -1, 0);
if (fd == -1)
{
printf ("! perf_event_open %m\n");
}

ps->perf_event_fd = fd;

fcntl(fd, F_SETFL, O_RDWR|O_NONBLOCK|O_ASYNC);
fcntl(fd, F_SETSIG, SIGPROF);
fcntl(fd, F_SETOWN, getpid());

ioctl(fd, PERF_EVENT_IOC_RESET, 0);

int err = ioctl(fd, PERF_EVENT_IOC_ENABLE, 0);
if (err != 0)
printf ("! perf_events enable\n");
}



/* Start profiling timer. */
static void profile_timer_start(ProfileState *ps)
{
int interval = ps->interval;
struct itimerval tm;
struct sigaction sa;
tm.it_value.tv_sec = tm.it_interval.tv_sec = interval / 1000;
tm.it_value.tv_usec = tm.it_interval.tv_usec = (interval % 1000) * 1000;
setitimer(ITIMER_PROF, &tm, NULL);
sa.sa_flags = SA_RESTART;
sa.sa_handler = profile_signal;
struct sigaction sa = {
.sa_flags = SA_RESTART,
.sa_handler = profile_signal
};

sigemptyset(&sa.sa_mask);
sigaction(SIGPROF, &sa, &ps->oldsa);

if (strcmp(ps->flavour, "vanilla") == 0)
{
int interval = ps->interval;
struct itimerval tm;
tm.it_value.tv_sec = tm.it_interval.tv_sec = interval / 1000;
tm.it_value.tv_usec = tm.it_interval.tv_usec = (interval % 1000) * 1000;
setitimer(ITIMER_PROF, &tm, NULL);
}
else
{
register_prof_events(ps);
}
}



/* Stop profiling timer. */
static void profile_timer_stop(ProfileState *ps)
{
struct itimerval tm;
tm.it_value.tv_sec = tm.it_interval.tv_sec = 0;
tm.it_value.tv_usec = tm.it_interval.tv_usec = 0;
setitimer(ITIMER_PROF, &tm, NULL);
sigaction(SIGPROF, &ps->oldsa, NULL);
if (ps->perf_event_fd)
{
ioctl(ps->perf_event_fd, PERF_EVENT_IOC_DISABLE, 0);
}
else
{
struct itimerval tm;
tm.it_value.tv_sec = tm.it_interval.tv_sec = 0;
tm.it_value.tv_usec = tm.it_interval.tv_usec = 0;
setitimer(ITIMER_PROF, &tm, NULL);
sigaction(SIGPROF, &ps->oldsa, NULL);
}
}

#elif LJ_PROFILE_PTHREAD
Expand Down Expand Up @@ -300,6 +463,8 @@ LUA_API void luaJIT_profile_start(lua_State *L, const char *mode,
{
ProfileState *ps = &profile_state;
int interval = LJ_PROFILE_INTERVAL_DEFAULT;
char *flavour;

while (*mode) {
int m = *mode++;
switch (m) {
Expand All @@ -315,6 +480,13 @@ LUA_API void luaJIT_profile_start(lua_State *L, const char *mode,
lj_trace_flushall(L);
break;
#endif
case 'S':
{
int k;
if (sscanf (mode, "[%m[^]]]%n", &flavour, &k) > 0)
mode += k;
}

default: /* Ignore unknown mode chars. */
break;
}
Expand All @@ -328,6 +500,7 @@ LUA_API void luaJIT_profile_start(lua_State *L, const char *mode,
ps->cb = cb;
ps->data = data;
ps->samples = 0;
ps->flavour = flavour;
lj_buf_init(L, &ps->sb);
profile_timer_start(ps);
}
Expand Down

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