Make dlfilter backend less aggressive about filtering out errors

Ref #260

src/perf_dlfilter.c

@@ -13,10 +13,14 @@ int filter_event_early(void *data, const struct perf_dlfilter_sample *sample,
       perf_dlfilter_fns.resolve_ip(ctx);
   const struct perf_dlfilter_al *resolved_addr =
       perf_dlfilter_fns.resolve_addr(ctx);
-  if (!resolved_ip || !resolved_ip->sym || !resolved_addr ||
-      !resolved_addr->sym ||
+
+  // Only filter out events we for sure don't want. It's better to be less aggressive than
+  // too aggressive, as being too aggressive will lead to broken traces, while being not
+  // aggressive enough just makes things slower.
+  if (resolved_ip && resolved_ip->sym && resolved_addr && resolved_addr->sym &&
       strcmp(resolved_ip->sym, resolved_addr->sym) == 0) {
     return 1;
   }
+
   return 0;
 }