Added documentation, bugfixes, improvements

- Added dlt-kpi.txt as asciidoc document.
- Fixed a bug where extremely high CPU- and IO-Wait times were
  calculated.
- CPU- and IO-Wait time are now being divided by CPU count.

3 files changed, 67 insertions, 8 deletions

diff --git a/src/kpi/dlt-kpi-common.c b/src/kpi/dlt-kpi-common.c
index c0c7767..26c4e28 100644
--- a/src/kpi/dlt-kpi-common.c
+++ b/src/kpi/dlt-kpi-common.c
@@ -26,6 +26,8 @@
 
 #include "dlt-kpi-common.h"
 
+static int dlt_kpi_cpu_count = -1;
+
 DltReturnValue dlt_kpi_read_file_compact(char *filename, char **target)
 {
     char buffer[BUFFER_SIZE];
@@ -66,3 +68,49 @@ DltReturnValue dlt_kpi_read_file(char* filename, char* buffer, uint maxLength)
 
     return DLT_RETURN_OK;
 }
+
+int dlt_kpi_read_cpu_count()
+{
+    char buffer[BUFFER_SIZE];
+    int ret = dlt_kpi_read_file("/proc/cpuinfo", buffer, sizeof(buffer));
+    if(ret != 0)
+    {
+        fprintf(stderr, "dlt_kpi_get_cpu_count(): Could not read /proc/cpuinfo\n");
+        return -1;
+    }
+
+    char* delim = "[] \t\n";
+    char* tok = strtok(buffer, delim);
+    if(tok == NULL)
+    {
+        fprintf(stderr, "dlt_kpi_get_cpu_count(): Could not extract token\n");
+        return -1;
+    }
+
+    int num = 0;
+    do
+    {
+        if(strcmp(tok, "processor") == 0)
+            num++;
+
+        tok = strtok(NULL, delim);
+    }
+    while(tok != NULL);
+
+    return num;
+}
+
+int dlt_kpi_get_cpu_count()
+{
+    if(dlt_kpi_cpu_count <= 0)
+    {
+        dlt_kpi_cpu_count = dlt_kpi_read_cpu_count();
+        if(dlt_kpi_cpu_count <= 0)
+        {
+            fprintf(stderr, "Could not get CPU count\n");
+            dlt_kpi_cpu_count = -1;
+        }
+    }
+
+    return dlt_kpi_cpu_count;
+}
diff --git a/src/kpi/dlt-kpi-common.h b/src/kpi/dlt-kpi-common.h
index 4e220a8..4777d6f 100644
--- a/src/kpi/dlt-kpi-common.h
+++ b/src/kpi/dlt-kpi-common.h
@@ -36,5 +36,6 @@
 
 DltReturnValue dlt_kpi_read_file(char* filename, char* buffer, uint maxLength);
 DltReturnValue dlt_kpi_read_file_compact(char *filename, char **target);
+int dlt_kpi_get_cpu_count();
 
 #endif /* SRC_KPI_DLT_KPI_COMMON_H_ */
diff --git a/src/kpi/dlt-kpi-process.c b/src/kpi/dlt-kpi-process.c
index d126551..168adf7 100644
--- a/src/kpi/dlt-kpi-process.c
+++ b/src/kpi/dlt-kpi-process.c
@@ -43,9 +43,11 @@ DltReturnValue dlt_kpi_process_update_io_wait(DltKpiProcess *process, unsigned l
 
     unsigned long int total_io_wait = dlt_kpi_read_process_stat_to_ulong(process->pid, 42);
 
+    int cpu_count = dlt_kpi_get_cpu_count();
+
     process->io_wait = (total_io_wait - process->last_io_wait) * 1000 / sysconf(_SC_CLK_TCK); // busy milliseconds since last update
-    if(time_dif_ms > 0)
-        process->io_wait = process->io_wait * 1000 / time_dif_ms; // busy milliseconds per second
+    if(time_dif_ms > 0 && cpu_count > 0)
+        process->io_wait = process->io_wait * 1000 / time_dif_ms / cpu_count; // busy milliseconds per second per CPU
 
     process->last_io_wait = total_io_wait;
 
@@ -65,9 +67,16 @@ DltReturnValue dlt_kpi_process_update_cpu_time(DltKpiProcess *process, unsigned
 
     unsigned long total_cpu_time = utime + stime;
 
-    process->cpu_time = (total_cpu_time - process->last_cpu_time) * 1000 / sysconf(_SC_CLK_TCK); // busy milliseconds since last update
-    if(time_dif_ms > 0)
-        process->cpu_time = process->cpu_time * 1000 / time_dif_ms; // busy milliseconds per second
+    if(process->last_cpu_time > 0 && process->last_cpu_time <= total_cpu_time)
+    {
+        int cpu_count = dlt_kpi_get_cpu_count();
+
+        process->cpu_time = (total_cpu_time - process->last_cpu_time) * 1000 / sysconf(_SC_CLK_TCK); // busy milliseconds since last update
+        if(time_dif_ms > 0 && cpu_count > 0)
+            process->cpu_time = process->cpu_time * 1000 / time_dif_ms / cpu_count; // busy milliseconds per second per CPU
+    }
+    else
+        process->cpu_time = 0;
 
     process->last_cpu_time = total_cpu_time;
 
@@ -319,13 +328,14 @@ unsigned long int dlt_kpi_read_process_stat_to_ulong(pid_t pid, unsigned int ind
     }
 
     char *buffer = NULL;
-    DltReturnValue tmp = dlt_kpi_read_process_file_to_str(pid, &buffer, "stat");
-    if(tmp < DLT_RETURN_OK)
+    if(dlt_kpi_read_process_file_to_str(pid, &buffer, "stat") < DLT_RETURN_OK)
     {
+        // fprintf(stderr, "dlt_kpi_read_process_stat_to_ulong(): Error while reading process stat file. Pid: %d. Requested index: %u\n", pid, index); // can happen if process closed shortly before
+
         if(buffer != NULL)
             free(buffer);
 
-        return tmp;
+        return 0;
     }
 
     char *tok = strtok(buffer, " \t\n");