systemctl: piece-meal strv extension is expensive

If we have many entries to add to an strv we really should try to be smarter than constantly realloc()ing the strv
array. Instead, grow it exponentially.

diff --git a/src/systemctl/systemctl.c b/src/systemctl/systemctl.c
index 94c99c4..73f5710 100644 (file)
--- a/src/systemctl/systemctl.c
+++ b/src/systemctl/systemctl.c
@@ -2658,14 +2658,25 @@ static int expand_names(sd_bus *bus, char **names, const char* suffix, char ***r
         if (!strv_isempty(globs)) {
                 _cleanup_(sd_bus_message_unrefp) sd_bus_message *reply = NULL;
                 _cleanup_free_ UnitInfo *unit_infos = NULL;
+                size_t allocated, n;
 
                 r = get_unit_list(bus, NULL, globs, &unit_infos, 0, &reply);
                 if (r < 0)
                         return r;
 
-                for (i = 0; i < r; i++)
-                        if (strv_extend(&mangled, unit_infos[i].id) < 0)
+                n = strv_length(mangled);
+                allocated = n + 1;
+
+                for (i = 0; i < r; i++) {
+                        if (!GREEDY_REALLOC(mangled, allocated, n+2))
+                                return log_oom();
+
+                        mangled[n] = strdup(unit_infos[i].id);
+                        if (!mangled[n])
                                 return log_oom();
+
+                        mangled[++n] = NULL;
+                }
         }
 
         *ret = mangled;