perf_counter tools: kerneltop: add real-time data acquisition thread

Decouple kerneltop display from event acquisition by introducing
a separate data acquisition thread. This fixes annnoying kerneltop
display refresh jitter and missed events.

Also add a -r <prio> option, to switch the data acquisition thread
to real-time priority.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Orig-LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 39 insertions, 18 deletions

diff --git a/Documentation/perf_counter/kerneltop.c b/Documentation/perf_counter/kerneltop.c
index 430810dae1fe..33b4fcf6e489 100644
--- a/Documentation/perf_counter/kerneltop.c
+++ b/Documentation/perf_counter/kerneltop.c
@@ -77,6 +77,8 @@
 #include <errno.h>
 #include <ctype.h>
 #include <time.h>
+#include <sched.h>
+#include <pthread.h>
 
 #include <sys/syscall.h>
 #include <sys/ioctl.h>
@@ -181,6 +183,7 @@ static int			tid				= -1;
 static int                      profile_cpu                     = -1;
 static int                      nr_cpus                         =  0;
 static int                      nmi                             =  1;
+static unsigned int             realtime_prio                   =  0;
 static int                      group                           =  0;
 static unsigned int             page_size;
 static unsigned int             mmap_pages                      =  16;
@@ -334,6 +337,7 @@ static void display_help(void)
         " -l                           # show scale factor for RR events\n"
         " -d delay  --delay=<seconds>  # sampling/display delay           [default:  2]\n"
         " -f CNT    --filter=CNT       # min-event-count filter          [default: 100]\n\n"
+        " -r prio   --realtime=<prio>  # event acquisition runs with SCHED_FIFO policy\n"
         " -s symbol --symbol=<symbol>  # function to be showed annotated one-shot\n"
         " -x path   --vmlinux=<path>   # the vmlinux binary, required for -s use\n"
         " -z        --zero             # zero counts after display\n"
@@ -620,7 +624,6 @@ static int compare(const void *__sym1, const void *__sym2)
         return sym_weight(sym1) < sym_weight(sym2);
 }
 
-static time_t                   last_refresh;
 static long                     events;
 static long                     userspace_events;
 static const char               CONSOLE_CLEAR[] = "";
@@ -634,6 +637,7 @@ static void print_sym_table(void)
         float events_per_sec = events/delay_secs;
         float kevents_per_sec = (events-userspace_events)/delay_secs;
 
+        events = userspace_events = 0;
         memcpy(tmp, sym_table, sizeof(sym_table[0])*sym_table_count);
         qsort(tmp, sym_table_count, sizeof(tmp[0]), compare);
 
@@ -714,8 +718,6 @@ static void print_sym_table(void)
         if (sym_filter_entry)
                 show_details(sym_filter_entry);
 
-        last_refresh = time(NULL);
-
         {
                 struct pollfd stdin_poll = { .fd = 0, .events = POLLIN };
 
@@ -726,6 +728,16 @@ static void print_sym_table(void)
         }
 }
 
+static void *display_thread(void *arg)
+{
+        printf("KernelTop refresh period: %d seconds\n", delay_secs);
+
+        while (!sleep(delay_secs))
+                print_sym_table();
+
+        return NULL;
+}
+
 static int read_symbol(FILE *in, struct sym_entry *s)
 {
         static int filter_match = 0;
@@ -1081,19 +1093,20 @@ static void process_options(int argc, char *argv[])
                         {"filter",      required_argument,      NULL, 'f'},
                         {"group",       required_argument,      NULL, 'g'},
                         {"help",        no_argument,            NULL, 'h'},
-                        {"scale",       no_argument,            NULL, 'l'},
                         {"nmi",         required_argument,      NULL, 'n'},
+                        {"mmap_info",   no_argument,            NULL, 'M'},
+                        {"mmap_pages",  required_argument,      NULL, 'm'},
+                        {"munmap_info", no_argument,            NULL, 'U'},
                         {"pid",         required_argument,      NULL, 'p'},
-                        {"vmlinux",     required_argument,      NULL, 'x'},
+                        {"realtime",    required_argument,      NULL, 'r'},
+                        {"scale",       no_argument,            NULL, 'l'},
                         {"symbol",      required_argument,      NULL, 's'},
                         {"stat",        no_argument,            NULL, 'S'},
+                        {"vmlinux",     required_argument,      NULL, 'x'},
                         {"zero",        no_argument,            NULL, 'z'},
-                        {"mmap_pages",  required_argument,      NULL, 'm'},
-                        {"mmap_info",   no_argument,            NULL, 'M'},
-                        {"munmap_info", no_argument,            NULL, 'U'},
                         {NULL,          0,                      NULL,  0 }
                 };
-                int c = getopt_long(argc, argv, "+:ac:C:d:De:f:g:hln:m:p:s:Sx:zMU",
+                int c = getopt_long(argc, argv, "+:ac:C:d:De:f:g:hln:m:p:r:s:Sx:zMU",
                                     long_options, &option_index);
                 if (c == -1)
                         break;
@@ -1127,6 +1140,7 @@ static void process_options(int argc, char *argv[])
                                 profile_cpu = -1;
                         }
                         tid                             =   atoi(optarg); break;
+                case 'r': realtime_prio                 =   atoi(optarg); break;
                 case 's': sym_filter                    = strdup(optarg); break;
                 case 'S': run_perfstat                  =              1; break;
                 case 'x': vmlinux                       = strdup(optarg); break;
@@ -1289,6 +1303,7 @@ int main(int argc, char *argv[])
         struct pollfd event_array[MAX_NR_CPUS * MAX_COUNTERS];
         struct mmap_data mmap_array[MAX_NR_CPUS][MAX_COUNTERS];
         struct perf_counter_hw_event hw_event;
+        pthread_t thread;
         int i, counter, group_fd, nr_poll = 0;
         unsigned int cpu;
         int ret;
@@ -1363,8 +1378,20 @@ int main(int argc, char *argv[])
                 }
         }
 
-        printf("KernelTop refresh period: %d seconds\n", delay_secs);
-        last_refresh = time(NULL);
+        if (pthread_create(&thread, NULL, display_thread, NULL)) {
+                printf("Could not create display thread.\n");
+                exit(-1);
+        }
+
+        if (realtime_prio) {
+                struct sched_param param;
+
+                param.sched_priority = realtime_prio;
+                if (sched_setscheduler(0, SCHED_FIFO, &param)) {
+                        printf("Could not set realtime priority.\n");
+                        exit(-1);
+                }
+        }
 
         while (1) {
                 int hits = events;
@@ -1374,14 +1401,8 @@ int main(int argc, char *argv[])
                                 mmap_read(&mmap_array[i][counter]);
                 }
 
-                if (time(NULL) >= last_refresh + delay_secs) {
-                        print_sym_table();
-                        events = userspace_events = 0;
-                }
-
                 if (hits == events)
-                        ret = poll(event_array, nr_poll, 1000);
-                hits = events;
+                        ret = poll(event_array, nr_poll, 100);
         }
 
         return 0;