[PATCH] blktrace: add support for checking events dropped by the kernel

diff --git a/blktrace.c b/blktrace.c
index 5c30d30021f3c8494ffad8a8b1d171127798a7cb..71e3b3e6d01b853f867142c84c4c07091f8d3cc9 100644 (file)
--- a/blktrace.c
+++ b/blktrace.c
@@ -34,6 +34,7 @@
 #include <sched.h>
 #include <ctype.h>
 #include <getopt.h>
+#include <errno.h>
 
 #include "blktrace.h"
 
@@ -649,9 +650,40 @@ static int start_devices(void)
        return 0;
 }
 
+static int get_dropped_count(const char *buts_name)
+{
+       int fd;
+       char tmp[MAXPATHLEN + 64];
+
+       snprintf(tmp, sizeof(tmp), "%s/block/%s/dropped",
+                relay_path, buts_name);
+
+       fd = open(tmp, O_RDONLY);
+       if (fd < 0) {
+               /*
+                * this may be ok, if the kernel doesn't support dropped counts
+                */
+               if (errno == ENOENT)
+                       return 0;
+
+               fprintf(stderr, "Couldn't open dropped file %s\n", tmp);
+               return -1;
+       }
+
+       if (read(fd, tmp, sizeof(tmp)) < 0) {
+               perror(tmp);
+               close(fd);
+               return -1;
+       }
+
+       close(fd);
+
+       return atoi(tmp);
+}
+
 static void show_stats(void)
 {
-       int i, j;
+       int i, j, dropped;
        struct device_information *dip;
        struct thread_information *tip;
        unsigned long long events_processed;
@@ -667,7 +699,9 @@ static void show_stats(void)
                               tip->cpu, tip->events_processed);
                        events_processed += tip->events_processed;
                }
-               printf("  Total:  %20lld events\n", events_processed);
+               dropped = get_dropped_count(dip->buts_name);
+               printf("  Total:  %20lld events (dropped %d)\n",
+                               events_processed, dropped);
        }
 }