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Ported perf code to work on arm and adjusted to changes in the kernel…
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… that broke mmap().

The kernel doesn't allow anymore to setup a perf fd with any cpu and the inherit flag
(to take into account threads created later on), so now we setup a fd/mmap area for each
cpu in the system.
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@illupus
illupus committed Aug 20, 2013
1 parent f36257e commit 25961ac
Showing 1 changed file with 143 additions and 39 deletions.
182 changes: 143 additions & 39 deletions mono/profiler/proflog.c
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Expand Up @@ -65,12 +65,12 @@
#endif

/* the architecture needs a memory fence */
#if defined(__linux__) && (defined(__i386__) || defined(__x86_64__))
#if defined(__linux__) && (defined(__i386__) || defined(__x86_64__) || defined(__arm__))
#include <unistd.h>
#include <sys/syscall.h>
#include "perf_event.h"
#define USE_PERF_EVENTS 1
static int read_perf_mmap (MonoProfiler* prof);
static int read_perf_mmap (MonoProfiler* prof, int cpu);
#endif

#define BUFFER_SIZE (4096 * 16)
Expand Down Expand Up @@ -1558,15 +1558,74 @@ dump_sample_hits (MonoProfiler *prof, StatBuffer *sbuf, int recurse)

#if USE_PERF_EVENTS
#ifndef __NR_perf_event_open
#ifdef __arm__
#define __NR_perf_event_open 364
#else
#define __NR_perf_event_open 241
#endif
#endif

static int
mono_cpu_count (void)
{
int count = 0;
#ifdef PLATFORM_ANDROID
/* Android tries really hard to save power by powering off CPUs on SMP phones which
* means the normal way to query cpu count returns a wrong value with userspace API.
* Instead we use /sys entries to query the actual hardware CPU count.
*/
char buffer[8] = {'\0'};
int present = open ("/sys/devices/system/cpu/present", O_RDONLY);
/* Format of the /sys entry is a cpulist of indexes which in the case
* of present is always of the form "0-(n-1)" when there is more than
* 1 core, n being the number of CPU cores in the system. Otherwise
* the value is simply 0
*/
if (present != -1 && read (present, (char*)buffer, sizeof (buffer)) > 3)
count = strtol (((char*)buffer) + 2, NULL, 10);
if (present != -1)
close (present);
if (count > 0)
return count + 1;
#endif
#ifdef _SC_NPROCESSORS_ONLN
count = sysconf (_SC_NPROCESSORS_ONLN);
if (count > 0)
return count;
#endif
#ifdef USE_SYSCTL
{
int mib [2];
size_t len = sizeof (int);
mib [0] = CTL_HW;
mib [1] = HW_NCPU;
if (sysctl (mib, 2, &count, &len, NULL, 0) == 0)
return count;
}
#endif
#ifdef HOST_WIN32
{
SYSTEM_INFO info;
GetSystemInfo (&info);
return info.dwNumberOfProcessors;
}
#endif
/* FIXME: warn */
return 1;
}

static int perf_fd = -1;
static void *mmap_base;
static struct perf_event_mmap_page *page_desc = NULL;
static int num_pages = 64;
typedef struct {
int perf_fd;
unsigned int prev_pos;
void *mmap_base;
struct perf_event_mmap_page *page_desc;
} PerfData ;

static PerfData *perf_data = NULL;
static int num_perf;
#define PERF_PAGES_SHIFT 4
static int num_pages = 1 << PERF_PAGES_SHIFT;
static unsigned int mmap_mask;
static unsigned int prev_pos = 0;

typedef struct {
struct perf_event_header h;
Expand All @@ -1587,24 +1646,25 @@ perf_event_syscall (struct perf_event_attr *attr, pid_t pid, int cpu, int group_
return syscall(/*__NR_perf_event_open*/ 298, attr, pid, cpu, group_fd, flags);
#elif defined(__i386__)
return syscall(/*__NR_perf_event_open*/ 336, attr, pid, cpu, group_fd, flags);
#elif defined(__arm__)
return syscall(/*__NR_perf_event_open*/ 364, attr, pid, cpu, group_fd, flags);
#else
return -1;
#endif
}

static int
setup_perf_map (void)
setup_perf_map (PerfData *perf)
{
mmap_mask = num_pages * getpagesize () - 1;
mmap_base = mmap (NULL, (num_pages + 1) * getpagesize (), PROT_READ|PROT_WRITE, MAP_SHARED, perf_fd, 0);
if (mmap_base == MAP_FAILED) {
perf->mmap_base = mmap (NULL, (num_pages + 1) * getpagesize (), PROT_READ|PROT_WRITE, MAP_SHARED, perf->perf_fd, 0);
if (perf->mmap_base == MAP_FAILED) {
if (do_debug)
printf ("failed mmap\n");
return 0;
}
page_desc = mmap_base;
perf->page_desc = perf->mmap_base;
if (do_debug)
printf ("mmap version: %d\n", page_desc->version);
printf ("mmap version: %d\n", perf->page_desc->version);
return 1;
}

Expand Down Expand Up @@ -1646,21 +1706,26 @@ dump_perf_hits (MonoProfiler *prof, void *buf, int size)

/* read events from the ring buffer */
static int
read_perf_mmap (MonoProfiler* prof)
read_perf_mmap (MonoProfiler* prof, int cpu)
{
PerfData *perf = perf_data + cpu;
unsigned char *buf;
unsigned char *data = (unsigned char*)mmap_base + getpagesize ();
unsigned int head = page_desc->data_head;
unsigned char *data = (unsigned char*)perf->mmap_base + getpagesize ();
unsigned int head = perf->page_desc->data_head;
int diff, size;
unsigned int old;

#if defined(__i386__)
asm volatile("lock; addl $0,0(%%esp)":::"memory");
#elif defined (__x86_64__)
asm volatile("lfence":::"memory");
#elif defined (__arm__)
((void(*)(void))0xffff0fa0)();
#else
asm volatile("":::"memory");
#endif

old = prev_pos;
old = perf->prev_pos;
diff = head - old;
if (diff < 0) {
if (do_debug)
Expand All @@ -1684,13 +1749,13 @@ read_perf_mmap (MonoProfiler* prof)
printf ("found bytes of events: %d\n", size);
dump_perf_hits (prof, buf, size);
old += size;
prev_pos = old;
page_desc->data_tail = old;
perf->prev_pos = old;
perf->page_desc->data_tail = old;
return 0;
}

static int
setup_perf_event (void)
setup_perf_event_for_cpu (PerfData *perf, int cpu)
{
struct perf_event_attr attr;
memset (&attr, 0, sizeof (attr));
Expand All @@ -1711,26 +1776,43 @@ setup_perf_event (void)
attr.freq = 1;
attr.sample_freq = sample_freq;

perf_fd = perf_event_syscall (&attr, getpid (), -1, -1, 0);
perf->perf_fd = perf_event_syscall (&attr, getpid (), cpu, -1, 0);
if (do_debug)
printf ("perf fd: %d, freq: %d, event: %llu\n", perf_fd, sample_freq, attr.config);
if (perf_fd < 0) {
if (perf_fd == -EPERM) {
printf ("perf fd: %d, freq: %d, event: %llu\n", perf->perf_fd, sample_freq, attr.config);
if (perf->perf_fd < 0) {
if (perf->perf_fd == -EPERM) {
fprintf (stderr, "Perf syscall denied, do \"echo 1 > /proc/sys/kernel/perf_event_paranoid\" as root to enable.\n");
} else {
if (do_debug)
perror ("open perf event");
}
return 0;
}
if (!setup_perf_map ()) {
close (perf_fd);
perf_fd = -1;
if (!setup_perf_map (perf)) {
close (perf->perf_fd);
perf->perf_fd = -1;
return 0;
}
return 1;
}

static int
setup_perf_event (void)
{
int i, count = 0;
mmap_mask = num_pages * getpagesize () - 1;
num_perf = mono_cpu_count ();
perf_data = calloc (num_perf, sizeof (PerfData));
for (i = 0; i < num_perf; ++i) {
count += setup_perf_event_for_cpu (perf_data + i, i);
}
if (count)
return 1;
free (perf_data);
perf_data = NULL;
return 0;
}

#endif /* USE_PERF_EVENTS */

static void
Expand All @@ -1746,8 +1828,11 @@ log_shutdown (MonoProfiler *prof)
}
#endif
#if USE_PERF_EVENTS
if (page_desc)
read_perf_mmap (prof);
if (perf_data) {
int i;
for (i = 0; i < num_perf; ++i)
read_perf_mmap (prof, i);
}
#endif
dump_sample_hits (prof, prof->stat_buffers, 1);
take_lock ();
Expand Down Expand Up @@ -1853,10 +1938,15 @@ helper_thread (void* arg)
max_fd = command_socket;
}
#if USE_PERF_EVENTS
if (perf_fd >= 0) {
FD_SET (perf_fd, &rfds);
if (max_fd < perf_fd)
max_fd = perf_fd;
if (perf_data) {
int i;
for ( i = 0; i < num_perf; ++i) {
if (perf_data [i].perf_fd < 0)
continue;
FD_SET (perf_data [i].perf_fd, &rfds);
if (max_fd < perf_data [i].perf_fd)
max_fd = perf_data [i].perf_fd;
}
}
#endif
tv.tv_sec = 1;
Expand Down Expand Up @@ -1889,16 +1979,30 @@ helper_thread (void* arg)
if (do_debug)
fprintf (stderr, "helper shutdown\n");
#if USE_PERF_EVENTS
if (perf_fd >= 0)
read_perf_mmap (prof);
if (perf_data) {
int i;
for ( i = 0; i < num_perf; ++i) {
if (perf_data [i].perf_fd < 0)
continue;
if (FD_ISSET (perf_data [i].perf_fd, &rfds))
read_perf_mmap (prof, i);
}
}
#endif
safe_dump (prof, ensure_logbuf (0));
return NULL;
}
#if USE_PERF_EVENTS
if (perf_fd >= 0 && FD_ISSET (perf_fd, &rfds)) {
read_perf_mmap (prof);
safe_dump (prof, ensure_logbuf (0));
if (perf_data) {
int i;
for ( i = 0; i < num_perf; ++i) {
if (perf_data [i].perf_fd < 0)
continue;
if (FD_ISSET (perf_data [i].perf_fd, &rfds)) {
read_perf_mmap (prof, i);
safe_dump (prof, ensure_logbuf (0));
}
}
}
#endif
if (command_socket >= 0 && FD_ISSET (command_socket, &rfds)) {
Expand Down Expand Up @@ -2041,7 +2145,7 @@ create_profiler (const char *filename)
#if USE_PERF_EVENTS
if (sample_type && !do_mono_sample)
need_helper_thread = setup_perf_event ();
if (perf_fd < 0) {
if (!perf_data) {
/* FIXME: warn if different freq or sample type */
do_mono_sample = 1;
}
Expand Down

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