wallet: warn if lockable memory limit is too low

src/common/util.cpp

@@ -728,6 +728,21 @@ std::string get_nix_version_display_string()
     return true;
   }
 
+  ssize_t get_lockable_memory()
+  {
+#ifdef __GLIBC__
+    struct rlimit rlim;
+    if (getrlimit(RLIMIT_MEMLOCK, &rlim) < 0)
+    {
+      MERROR("Failed to determine the lockable memory limit");
+      return -1;
+    }
+    return rlim.rlim_cur;
+#else
+    return -1;
+#endif
+  }
+
   bool on_startup()
   {
     mlog_configure("", true);

src/common/util.h

@@ -221,6 +221,8 @@ namespace tools
 
   void set_strict_default_file_permissions(bool strict);
 
+  ssize_t get_lockable_memory();
+
   void set_max_concurrency(unsigned n);
   unsigned get_max_concurrency();
 

src/wallet/wallet_args.cpp

@@ -211,6 +211,14 @@ namespace wallet_args
 
     Print(print) << boost::format(wallet_args::tr("Logging to %s")) % log_path;
 
+    const ssize_t lockable_memory = tools::get_lockable_memory();
+    if (lockable_memory >= 0 && lockable_memory < 256 * 4096) // 256 pages -> at least 256 secret keys and other such small/medium objects
+      Print(print) << tr("WARNING: You may not have a high enough lockable memory limit")
+#ifdef ELPP_OS_UNIX
+        << ", " << tr("see ulimit -l")
+#endif
+        ;
+
     return {std::move(vm), should_terminate};
   }
 }