zfs_arc plugin: Move reading of kstat values into separate functions.

This way error handling can be done in a central place and we can do this more
carefully overall.

diff --git a/src/zfs_arc.c b/src/zfs_arc.c
index ea05bf8..e77569f 100644 (file)
--- a/src/zfs_arc.c
+++ b/src/zfs_arc.c
@@ -54,12 +54,38 @@ static void za_submit_gauge (const char* type, const char* type_instance, gauge_
        za_submit (type, type_instance, &vv, 1);
 }
 
-static void za_submit_derive (const char* type, const char* type_instance, derive_t dv)
+static int za_read_derive (kstat_t *ksp, const char *kstat_value,
+    const char *type, const char *type_instance)
 {
-       value_t vv;
+  long long tmp;
+  value_t v;
+
+  tmp = get_kstat_value (ksp, kstat_value);
+  if (tmp == -1LL)
+  {
+    ERROR ("zfs_arc plugin: Reading kstat value \"%s\" failed.", kstat_value);
+    return (-1);
+  }
+
+  v.derive = (derive_t) tmp;
+  za_submit (type, type_instance, /* values = */ &v, /* values_num = */ 1);
+}
 
-       vv.derive = dv;
-       za_submit (type, type_instance, &vv, 1);
+static int za_read_gauge (kstat_t *ksp, const char *kstat_value,
+    const char *type, const char *type_instance)
+{
+  long long tmp;
+  value_t v;
+
+  tmp = get_kstat_value (ksp, kstat_value);
+  if (tmp == -1LL)
+  {
+    ERROR ("zfs_arc plugin: Reading kstat value \"%s\" failed.", kstat_value);
+    return (-1);
+  }
+
+  v.gauge = (gauge_t) tmp;
+  za_submit (type, type_instance, /* values = */ &v, /* values_num = */ 1);
 }
 
 static void za_submit_ratio (const char* type_instance, gauge_t hits, gauge_t misses)
@@ -79,21 +105,8 @@ static void za_submit_ratio (const char* type_instance, gauge_t hits, gauge_t mi
 
 static int za_read (void)
 {
-       gauge_t  arc_size, l2_size;
-       derive_t demand_data_hits,
-                demand_metadata_hits,
-                prefetch_data_hits,
-                prefetch_metadata_hits,
-                demand_data_misses,
-                demand_metadata_misses,
-                prefetch_data_misses,
-                prefetch_metadata_misses;
        gauge_t  arc_hits, arc_misses, l2_hits, l2_misses;
        value_t  l2_io[2];
-       derive_t mutex_miss;
-       derive_t allocated, deleted, stolen;
-       derive_t evict_l2_cached, evict_l2_eligible, evict_l2_ineligible;
-       derive_t hash_collisions;
 
        get_kstat (&ksp, "zfs", 0, "arcstats");
        if (ksp == NULL)
@@ -103,53 +116,32 @@ static int za_read (void)
        }
 
        /* Sizes */
-       arc_size   = get_kstat_value(ksp, "size");
-       l2_size    = get_kstat_value(ksp, "l2_size");
+       za_read_gauge (ksp, "size",    "cache_size", "arc");
+       za_read_gauge (ksp, "l2_size", "cache_size", "L2");
 
-       za_submit_gauge ("cache_size", "arc", arc_size);
-       za_submit_gauge ("cache_size", "L2", l2_size);
+        /* Operations */
+       za_read_derive (ksp, "allocated","cache_operation", "allocated");
+       za_read_derive (ksp, "deleted",  "cache_operation", "deleted");
+       za_read_derive (ksp, "stolen",   "cache_operation", "stolen");
 
-       mutex_miss = get_kstat_value (ksp, "mutex_miss");
-       za_submit_derive ("mutex_operation", "miss", mutex_miss);
-
-       allocated = get_kstat_value(ksp, "allocated");
-       deleted   = get_kstat_value(ksp, "deleted");
-       stolen    = get_kstat_value(ksp, "stolen");
-       za_submit_derive ("cache_operation", "allocated", allocated);
-       za_submit_derive ("cache_operation", "deleted",   deleted);
-       za_submit_derive ("cache_operation", "stolen",    stolen);
-
-       hash_collisions = get_kstat_value(ksp, "hash_collisions");
-       za_submit_derive ("hash_collisions", "", hash_collisions);
-       
-       evict_l2_cached          = get_kstat_value(ksp, "evict_l2_cached");
-       evict_l2_eligible        = get_kstat_value(ksp, "evict_l2_eligible");
-       evict_l2_ineligible      = get_kstat_value(ksp, "evict_l2_ineligible");
+        /* Issue indicators */
+        za_read_derive (ksp, "mutex_miss", "mutex_operation", "miss");
+       za_read_derive (ksp, "hash_collisions", "hash_collisions", "");
        
-       za_submit_derive ("cache_eviction", "cached",     evict_l2_cached);
-       za_submit_derive ("cache_eviction", "eligible",   evict_l2_eligible);
-       za_submit_derive ("cache_eviction", "ineligible", evict_l2_ineligible);
+        /* Evictions */
+       za_read_derive (ksp, "evict_l2_cached",     "cache_eviction", "cached");
+       za_read_derive (ksp, "evict_l2_eligible",   "cache_eviction", "eligible");
+       za_read_derive (ksp, "evict_l2_ineligible", "cache_eviction", "ineligible");
 
        /* Hits / misses */
-       demand_data_hits       = get_kstat_value(ksp, "demand_data_hits");
-       demand_metadata_hits   = get_kstat_value(ksp, "demand_metadata_hits");
-       prefetch_data_hits     = get_kstat_value(ksp, "prefetch_data_hits");
-       prefetch_metadata_hits = get_kstat_value(ksp, "prefetch_metadata_hits");
-
-       demand_data_misses       = get_kstat_value(ksp, "demand_data_misses");
-       demand_metadata_misses   = get_kstat_value(ksp, "demand_metadata_misses");
-       prefetch_data_misses     = get_kstat_value(ksp, "prefetch_data_misses");
-       prefetch_metadata_misses = get_kstat_value(ksp, "prefetch_metadata_misses");
-
-       za_submit_derive ("cache_result", "demand_data-hit",       demand_data_hits);
-       za_submit_derive ("cache_result", "demand_metadata-hit",   demand_metadata_hits);
-       za_submit_derive ("cache_result", "prefetch_data-hit",     prefetch_data_hits);
-       za_submit_derive ("cache_result", "prefetch_metadata-hit", prefetch_metadata_hits);
-
-       za_submit_derive ("cache_result", "demand_data-miss",       demand_data_misses);
-       za_submit_derive ("cache_result", "demand_metadata-miss",   demand_metadata_misses);
-       za_submit_derive ("cache_result", "prefetch_data-miss",     prefetch_data_misses);
-       za_submit_derive ("cache_result", "prefetch_metadata-miss", prefetch_metadata_misses);
+       za_read_derive (ksp, "demand_data_hits",         "cache_result", "demand_data-hit");
+       za_read_derive (ksp, "demand_metadata_hits",     "cache_result", "demand_metadata-hit");
+       za_read_derive (ksp, "prefetch_data_hits",       "cache_result", "prefetch_data-hit");
+       za_read_derive (ksp, "prefetch_metadata_hits",   "cache_result", "prefetch_metadata-hit");
+       za_read_derive (ksp, "demand_data_misses",       "cache_result", "demand_data-miss");
+       za_read_derive (ksp, "demand_metadata_misses",   "cache_result", "demand_metadata-miss");
+       za_read_derive (ksp, "prefetch_data_misses",     "cache_result", "prefetch_data-miss");
+       za_read_derive (ksp, "prefetch_metadata_misses", "cache_result", "prefetch_metadata-miss");
 
        /* Ratios */
        arc_hits   = (gauge_t) get_kstat_value(ksp, "hits");