Simplify computation of next snapshot time.
authorAndre Noll <maan@systemlinux.org>
Thu, 27 Aug 2009 14:27:29 +0000 (16:27 +0200)
committerAndre Noll <maan@systemlinux.org>
Fri, 28 Aug 2009 09:02:05 +0000 (11:02 +0200)
Using an int64_t rather than a struct timeval for the next snapshot time
makes the code simpler and more readable as we don't have to use the
tv_xxx() functions to perform manipulations.

dss.c

diff --git a/dss.c b/dss.c
index f04be8f..f82664f 100644 (file)
--- a/dss.c
+++ b/dss.c
@@ -47,7 +47,7 @@ static int create_process_stopped;
 /** Process id of current pre-remove/rm/post-remove process. */
 static pid_t remove_pid;
 /** When the next snapshot is due. */
-static struct timeval next_snapshot_time;
+static int64_t next_snapshot_time;
 /** When to try to remove something. */
 static struct timeval next_removal_check;
 /** Creation time of the snapshot currently being created. */
@@ -153,17 +153,15 @@ static void dss_get_snapshot_list(struct snapshot_list *sl)
 
 static int next_snapshot_is_due(void)
 {
-       struct timeval now, unit_interval = {.tv_sec = 24 * 3600 * conf.unit_interval_arg},
-               tmp, diff;
-       int64_t x = 0;
+       int64_t x = 0, now = get_current_time(), unit_interval
+               = 24 * 3600 * conf.unit_interval_arg;
        unsigned wanted = desired_number_of_snapshots(0, conf.num_intervals_arg),
                num_complete_snapshots = 0;
        int i, ret;
        struct snapshot *s = NULL;
        struct snapshot_list sl;
 
-       gettimeofday(&now, NULL);
-       if (tv_diff(&next_snapshot_time, &now, NULL) > 0)
+       if (next_snapshot_time > now)
                return 0;
        assert(snapshot_creation_status == HS_READY);
        current_snapshot_creation_time = 0;
@@ -175,27 +173,20 @@ static int next_snapshot_is_due(void)
                x += s->completion_time - s->creation_time;
        }
        assert(x >= 0);
-       if (num_complete_snapshots)
-               x /= num_complete_snapshots; /* avg time to create one snapshot */
-       x *= wanted; /* time to create all snapshots in interval 0 */
-       tmp.tv_sec = x;
-       tmp.tv_usec = 0;
-       ret = tv_diff(&unit_interval, &tmp, &diff); /* total sleep time per unit interval */
-       if (ret < 0 || !s) { /* unit_interval < tmp or no snapshot */
-               ret = 1;
-               goto out;
-       }
 
-       tv_divide(wanted, &diff, &tmp); /* sleep time between two snapshots */
-       diff.tv_sec = s->completion_time; /* completion time of the latest snapshot */
-       diff.tv_usec = 0;
-       tv_add(&diff, &tmp, &next_snapshot_time);
-       ret = (tv_diff(&now, &next_snapshot_time, &diff) < 0)? 0 : 1;
+       next_snapshot_time = now;
+       if (num_complete_snapshots == 0)
+               goto out;
+       x /= num_complete_snapshots; /* avg time to create one snapshot */
+       if (unit_interval < x * wanted) /* oops, no sleep at all */
+               goto out;
+       next_snapshot_time = s->completion_time + unit_interval / wanted - x;
 out:
        free_snapshot_list(&sl);
+       ret = next_snapshot_time <= now;
        if (ret == 0)
                DSS_DEBUG_LOG("next snapshot due in %lu seconds\n",
-                       tv2ms(&diff) / 1000);
+                       next_snapshot_time - now);
        else
                DSS_DEBUG_LOG("next snapshot: now\n");
        return ret;
@@ -707,8 +698,7 @@ static int handle_rsync_exit(int status)
                DSS_WARNING_LOG("rsync process %d returned %d -- restarting\n",
                        (int)create_pid, es);
                snapshot_creation_status = HS_NEEDS_RESTART;
-               gettimeofday(&next_snapshot_time, NULL);
-               next_snapshot_time.tv_sec += 60;
+               next_snapshot_time = get_current_time() + 60;
                ret = 1;
                goto out;
        }
@@ -748,8 +738,7 @@ static int handle_pre_create_hook_exit(int status)
                        DSS_NOTICE_LOG("deferring snapshot creation...\n");
                        warn_count = 60; /* warn only once per hour */
                }
-               gettimeofday(&next_snapshot_time, NULL);
-               next_snapshot_time.tv_sec += 60;
+               next_snapshot_time = get_current_time() + 60;
                snapshot_creation_status = HS_READY;
                ret = 0;
                goto out;