diff --git a/include/dwarfs/filesystem_v2.h b/include/dwarfs/filesystem_v2.h
index 8a14b5ad..518d33c5 100644
--- a/include/dwarfs/filesystem_v2.h
+++ b/include/dwarfs/filesystem_v2.h
@@ -42,7 +42,7 @@ struct statvfs;
 
 namespace dwarfs {
 
-struct block_cache_options;
+struct filesystem_options;
 struct iovec_read_buf;
 
 class filesystem_writer;
@@ -55,7 +55,7 @@ class filesystem_v2 {
   filesystem_v2(logger& lgr, std::shared_ptr<mmif> mm);
 
   filesystem_v2(logger& lgr, std::shared_ptr<mmif> mm,
-                const block_cache_options& bc_options,
+                const filesystem_options& options,
                 const struct ::stat* stat_defaults = nullptr,
                 int inode_offset = 0);
 
diff --git a/include/dwarfs/logger.h b/include/dwarfs/logger.h
index fefe4ade..c6eec044 100644
--- a/include/dwarfs/logger.h
+++ b/include/dwarfs/logger.h
@@ -31,6 +31,7 @@
 #include <sstream>
 #include <stdexcept>
 #include <string>
+#include <string_view>
 #include <tuple>
 #include <type_traits>
 #include <utility>
@@ -60,7 +61,7 @@ class logger {
     policy_name_ = name;
   }
 
-  static level_type parse_level(const std::string& level);
+  static level_type parse_level(std::string_view level);
 
  private:
   std::string policy_name_; // TODO: const?
@@ -119,14 +120,17 @@ class timed_level_logger {
       : data_(std::move(ll.data_)) {}
 
   ~timed_level_logger() {
-    std::chrono::duration<double> sec =
-        std::chrono::high_resolution_clock::now() - data_->start_time;
-    data_->oss << " [" << time_with_unit(sec.count()) << "]";
-    data_->lgr.write(data_->level, data_->oss.str());
+    if (data_->output) {
+      std::chrono::duration<double> sec =
+          std::chrono::high_resolution_clock::now() - data_->start_time;
+      data_->oss << " [" << time_with_unit(sec.count()) << "]";
+      data_->lgr.write(data_->level, data_->oss.str());
+    }
   }
 
   template <typename T>
   timed_level_logger& operator<<(const T& val) {
+    data_->output = true;
     data_->oss << val;
     return *this;
   }
@@ -142,6 +146,7 @@ class timed_level_logger {
     std::ostringstream oss;
     const logger::level_type level;
     std::chrono::time_point<std::chrono::high_resolution_clock> start_time;
+    bool output{false};
   };
 
   std::unique_ptr<data> data_;
diff --git a/include/dwarfs/options.h b/include/dwarfs/options.h
index d2ac2ae1..f7f66845 100644
--- a/include/dwarfs/options.h
+++ b/include/dwarfs/options.h
@@ -26,18 +26,28 @@
 
 namespace dwarfs {
 
+enum class mlock_mode { NONE, TRY, MUST };
+
 struct block_cache_options {
   size_t max_bytes{0};
   size_t num_workers{0};
   double decompress_ratio{1.0};
 };
 
-enum class file_order_mode { NONE, PATH, SCRIPT, SIMILARITY };
+struct filesystem_options {
+  mlock_mode lock_mode{mlock_mode::NONE};
+  block_cache_options block_cache;
+};
 
-std::ostream& operator<<(std::ostream& os, file_order_mode mode);
+enum class file_order_mode { NONE, PATH, SCRIPT, SIMILARITY };
 
 struct scanner_options {
   file_order_mode file_order;
   bool no_time;
 };
+
+std::ostream& operator<<(std::ostream& os, file_order_mode mode);
+
+mlock_mode parse_mlock_mode(std::string_view mode);
+
 } // namespace dwarfs
diff --git a/src/dwarfs.cpp b/src/dwarfs.cpp
index d4740047..2d3b92f2 100644
--- a/src/dwarfs.cpp
+++ b/src/dwarfs.cpp
@@ -50,9 +50,11 @@ struct options {
   const char* cachesize_str;        // TODO: const?? -> use string?
   const char* debuglevel_str;       // TODO: const?? -> use string?
   const char* workers_str;          // TODO: const?? -> use string?
+  const char* mlock_str;            // TODO: const?? -> use string?
   const char* decompress_ratio_str; // TODO: const?? -> use string?
   size_t cachesize;
   size_t workers;
+  mlock_mode lock_mode;
   double decompress_ratio;
   logger::level_type debuglevel;
   struct ::stat stat_defaults;
@@ -68,32 +70,40 @@ struct options {
 
 const struct fuse_opt dwarfs_opts[] = {
     // TODO: user, group, atime, mtime, ctime for those fs who don't have it?
-    //       second level cachesize
     DWARFS_OPT("cachesize=%s", cachesize_str, 0),
     DWARFS_OPT("debuglevel=%s", debuglevel_str, 0),
     DWARFS_OPT("workers=%s", workers_str, 0),
-    DWARFS_OPT("decratio=%s", decompress_ratio_str, 0), FUSE_OPT_END};
+    DWARFS_OPT("mlock=%s", mlock_str, 0),
+    DWARFS_OPT("decratio=%s", decompress_ratio_str, 0),
+    FUSE_OPT_END};
 
 options opts;
 stream_logger s_lgr(std::cerr);
 std::shared_ptr<filesystem_v2> s_fs;
+struct fuse_session* s_session;
 
 void op_init(void* /*userdata*/, struct fuse_conn_info* /*conn*/) {
   DEBUG_FUNC("")
 
   log_proxy<debug_logger_policy> log(s_lgr);
 
-  auto ti = log.timed_info();
+  try {
+    auto ti = log.timed_info();
 
-  block_cache_options bco;
-  bco.max_bytes = opts.cachesize;
-  bco.num_workers = opts.workers;
-  bco.decompress_ratio = opts.decompress_ratio;
-  s_fs = std::make_shared<filesystem_v2>(
-      s_lgr, std::make_shared<mmap>(opts.fsimage), bco, &opts.stat_defaults,
-      FUSE_ROOT_ID);
+    filesystem_options options;
+    options.lock_mode = opts.lock_mode;
+    options.block_cache.max_bytes = opts.cachesize;
+    options.block_cache.num_workers = opts.workers;
+    options.block_cache.decompress_ratio = opts.decompress_ratio;
+    s_fs = std::make_shared<filesystem_v2>(
+        s_lgr, std::make_shared<mmap>(opts.fsimage), options,
+        &opts.stat_defaults, FUSE_ROOT_ID);
 
-  ti << "file system initialized";
+    ti << "file system initialized";
+  } catch (const std::exception& e) {
+    log.error() << "error initializing file system: " << e.what();
+    fuse_session_exit(s_session);
+  }
 }
 
 void op_destroy(void* /*userdata*/) {
@@ -376,8 +386,9 @@ void usage(const char* progname) {
             << "DWARFS options:\n"
             << "    -o cachesize=SIZE      set size of block cache (512M)\n"
             << "    -o workers=NUM         number of worker threads (2)\n"
+            << "    -o mlock=NAME          mlock mode: (none), try, must\n"
             << "    -o decratio=NUM        ratio for full decompression (0.8)\n"
-            << "    -o debuglevel=NAME     error, warn, info, debug, trace\n"
+            << "    -o debuglevel=NAME     error, warn, (info), debug, trace\n"
             << std::endl;
 
   fuse_cmdline_help();
@@ -438,27 +449,27 @@ int run_fuse(struct fuse_args& args) {
   // fsops.getxattr = op_getxattr;
   // fsops.listxattr = op_listxattr;
 
-  auto se = fuse_session_new(&args, &fsops, sizeof(fsops), nullptr);
+  s_session = fuse_session_new(&args, &fsops, sizeof(fsops), nullptr);
   int err = 1;
 
-  if (se) {
-    if (fuse_set_signal_handlers(se) == 0) {
-      if (fuse_session_mount(se, fuse_opts.mountpoint) == 0) {
+  if (s_session) {
+    if (fuse_set_signal_handlers(s_session) == 0) {
+      if (fuse_session_mount(s_session, fuse_opts.mountpoint) == 0) {
         if (fuse_daemonize(fuse_opts.foreground) == 0) {
           if (fuse_opts.singlethread) {
-            err = fuse_session_loop(se);
+            err = fuse_session_loop(s_session);
           } else {
             struct fuse_loop_config config;
             config.clone_fd = fuse_opts.clone_fd;
             config.max_idle_threads = fuse_opts.max_idle_threads;
-            err = fuse_session_loop_mt(se, &config);
+            err = fuse_session_loop_mt(s_session, &config);
           }
         }
-        fuse_session_unmount(se);
+        fuse_session_unmount(s_session);
       }
-      fuse_remove_signal_handlers(se);
+      fuse_remove_signal_handlers(s_session);
     }
-    fuse_session_destroy(se);
+    fuse_session_destroy(s_session);
   }
 
   ::free(fuse_opts.mountpoint);
@@ -485,6 +496,8 @@ int main(int argc, char* argv[]) {
                         ? logger::parse_level(opts.debuglevel_str)
                         : logger::INFO;
   opts.workers = opts.workers_str ? folly::to<size_t>(opts.workers_str) : 2;
+  opts.lock_mode =
+      opts.mlock_str ? parse_mlock_mode(opts.mlock_str) : mlock_mode::NONE;
   opts.decompress_ratio = opts.decompress_ratio_str
                               ? folly::to<double>(opts.decompress_ratio_str)
                               : 0.8;
diff --git a/src/dwarfs/filesystem_v2.cpp b/src/dwarfs/filesystem_v2.cpp
index 0b17b266..c6cf0721 100644
--- a/src/dwarfs/filesystem_v2.cpp
+++ b/src/dwarfs/filesystem_v2.cpp
@@ -19,6 +19,7 @@
  * along with dwarfs.  If not, see <https://www.gnu.org/licenses/>.
  */
 
+#include <cerrno>
 #include <cstddef>
 #include <cstring>
 #include <optional>
@@ -26,8 +27,11 @@
 #include <unordered_map>
 #include <vector>
 
+#include <sys/mman.h>
 #include <sys/statvfs.h>
 
+#include <boost/system/system_error.hpp>
+
 #include <folly/Range.h>
 
 #include <fmt/format.h>
@@ -141,7 +145,9 @@ make_metadata(logger& lgr, std::shared_ptr<mmif> mm,
               section_map const& sections, std::vector<uint8_t>& schema_buffer,
               std::vector<uint8_t>& meta_buffer,
               const struct ::stat* stat_defaults = nullptr,
-              int inode_offset = 0, bool force_buffers = false) {
+              int inode_offset = 0, bool force_buffers = false,
+              mlock_mode lock_mode = mlock_mode::NONE) {
+  log_proxy<debug_logger_policy> log(lgr);
   auto schema_it = sections.find(section_type::METADATA_V2_SCHEMA);
   auto meta_it = sections.find(section_type::METADATA_V2);
 
@@ -153,18 +159,32 @@ make_metadata(logger& lgr, std::shared_ptr<mmif> mm,
     throw std::runtime_error("no metadata found");
   }
 
+  auto meta_section =
+      get_section_data(mm, meta_it->second, meta_buffer, force_buffers);
+
+  if (lock_mode != mlock_mode::NONE) {
+    int rv = ::mlock(meta_section.data(), meta_section.size());
+    if (rv != 0) {
+      boost::system::error_code ec(errno, boost::system::generic_category());
+      if (lock_mode == mlock_mode::MUST) {
+        throw boost::system::system_error(ec, "mlock");
+      } else {
+        log.warn() << "mlock() failed: " << ec.message();
+      }
+    }
+  }
+
   return metadata_v2(
       lgr,
       get_section_data(mm, schema_it->second, schema_buffer, force_buffers),
-      get_section_data(mm, meta_it->second, meta_buffer, force_buffers),
-      stat_defaults, inode_offset);
+      meta_section, stat_defaults, inode_offset);
 }
 
 template <typename LoggerPolicy>
 class filesystem_ : public filesystem_v2::impl {
  public:
   filesystem_(logger& lgr_, std::shared_ptr<mmif> mm,
-              const block_cache_options& bc_options,
+              const filesystem_options& options,
               const struct ::stat* stat_defaults, int inode_offset);
 
   void dump(std::ostream& os, int detail_level) const override;
@@ -198,13 +218,13 @@ class filesystem_ : public filesystem_v2::impl {
 
 template <typename LoggerPolicy>
 filesystem_<LoggerPolicy>::filesystem_(logger& lgr, std::shared_ptr<mmif> mm,
-                                       const block_cache_options& bc_options,
+                                       const filesystem_options& options,
                                        const struct ::stat* stat_defaults,
                                        int inode_offset)
     : log_(lgr)
     , mm_(mm) {
   filesystem_parser parser(mm_);
-  block_cache cache(lgr, bc_options);
+  block_cache cache(lgr, options.block_cache);
 
   section_map sections;
 
@@ -223,7 +243,7 @@ filesystem_<LoggerPolicy>::filesystem_(logger& lgr, std::shared_ptr<mmif> mm,
   std::vector<uint8_t> schema_buffer;
 
   meta_ = make_metadata(lgr, mm_, sections, schema_buffer, meta_buffer_,
-                        stat_defaults, inode_offset);
+                        stat_defaults, inode_offset, false, options.lock_mode);
 
   log_.debug() << "read " << cache.block_count() << " blocks and "
                << meta_.size() << " bytes of metadata";
@@ -341,15 +361,15 @@ ssize_t filesystem_<LoggerPolicy>::readv(uint32_t inode, iovec_read_buf& buf,
 } // namespace
 
 filesystem_v2::filesystem_v2(logger& lgr, std::shared_ptr<mmif> mm)
-    : filesystem_v2(lgr, std::move(mm), block_cache_options()) {}
+    : filesystem_v2(lgr, std::move(mm), filesystem_options()) {}
 
 filesystem_v2::filesystem_v2(logger& lgr, std::shared_ptr<mmif> mm,
-                             const block_cache_options& bc_options,
+                             const filesystem_options& options,
                              const struct ::stat* stat_defaults,
                              int inode_offset)
     : impl_(make_unique_logging_object<filesystem_v2::impl, filesystem_,
                                        logger_policies>(
-          lgr, std::move(mm), bc_options, stat_defaults, inode_offset)) {}
+          lgr, std::move(mm), options, stat_defaults, inode_offset)) {}
 
 void filesystem_v2::rewrite(logger& lgr, progress& prog,
                             std::shared_ptr<mmif> mm,
diff --git a/src/dwarfs/logger.cpp b/src/dwarfs/logger.cpp
index b5ca5c6b..d4ffec9f 100644
--- a/src/dwarfs/logger.cpp
+++ b/src/dwarfs/logger.cpp
@@ -29,6 +29,8 @@
 
 #include <boost/date_time/posix_time/posix_time.hpp>
 
+#include <fmt/format.h>
+
 #include "dwarfs/logger.h"
 
 namespace dwarfs {
@@ -69,18 +71,23 @@ void backtrace(std::ostream& os) {
 }
 } // namespace
 
-logger::level_type logger::parse_level(const std::string& level) {
-  if (level == "error")
+logger::level_type logger::parse_level(std::string_view level) {
+  if (level == "error") {
     return ERROR;
-  if (level == "warn")
+  }
+  if (level == "warn") {
     return WARN;
-  if (level == "info")
+  }
+  if (level == "info") {
     return INFO;
-  if (level == "debug")
+  }
+  if (level == "debug") {
     return DEBUG;
-  if (level == "trace")
+  }
+  if (level == "trace") {
     return TRACE;
-  throw std::runtime_error("invalid logger level");
+  }
+  throw std::runtime_error(fmt::format("invalid logger level: {}", level));
 }
 
 stream_logger::stream_logger(std::ostream& os, level_type threshold)
diff --git a/src/dwarfs/mmap.cpp b/src/dwarfs/mmap.cpp
index 604751ce..890cf4c1 100644
--- a/src/dwarfs/mmap.cpp
+++ b/src/dwarfs/mmap.cpp
@@ -26,6 +26,7 @@
 #include <sys/stat.h>
 #include <unistd.h>
 
+#include <boost/system/error_code.hpp>
 #include <boost/system/system_error.hpp>
 
 #include "dwarfs/mmap.h"
diff --git a/src/dwarfs/options.cpp b/src/dwarfs/options.cpp
index 31661cd6..887c73f4 100644
--- a/src/dwarfs/options.cpp
+++ b/src/dwarfs/options.cpp
@@ -22,6 +22,8 @@
 #include <ostream>
 #include <string>
 
+#include <fmt/format.h>
+
 #include "dwarfs/options.h"
 
 namespace dwarfs {
@@ -49,4 +51,17 @@ std::ostream& operator<<(std::ostream& os, file_order_mode mode) {
   return os << modestr;
 }
 
+mlock_mode parse_mlock_mode(std::string_view mode) {
+  if (mode == "none") {
+    return mlock_mode::NONE;
+  }
+  if (mode == "try") {
+    return mlock_mode::TRY;
+  }
+  if (mode == "must") {
+    return mlock_mode::MUST;
+  }
+  throw std::runtime_error(fmt::format("invalid lock mode: {}", mode));
+}
+
 } // namespace dwarfs
diff --git a/src/dwarfsbench.cpp b/src/dwarfsbench.cpp
index d6bf6651..a02ef6b6 100644
--- a/src/dwarfsbench.cpp
+++ b/src/dwarfsbench.cpp
@@ -39,7 +39,8 @@ using namespace dwarfs;
 namespace {
 
 int dwarfsbench(int argc, char** argv) {
-  std::string filesystem, cache_size_str, decompress_ratio_str, log_level;
+  std::string filesystem, cache_size_str, lock_mode_str, decompress_ratio_str,
+      log_level;
   size_t num_workers;
   size_t num_readers;
 
@@ -58,6 +59,9 @@ int dwarfsbench(int argc, char** argv) {
     ("cache-size,s",
         po::value<std::string>(&cache_size_str)->default_value("256m"),
         "block cache size")
+    ("lock-mode,m",
+        po::value<std::string>(&cache_size_str)->default_value("none"),
+        "mlock mode (none, try, must)")
     ("decompress-ratio,r",
         po::value<std::string>(&decompress_ratio_str)->default_value("0.8"),
         "block cache size")
@@ -80,14 +84,15 @@ int dwarfsbench(int argc, char** argv) {
   }
 
   stream_logger lgr(std::cerr, logger::parse_level(log_level));
-  block_cache_options bco;
+  filesystem_options fsopts;
 
-  bco.max_bytes = parse_size_with_unit(cache_size_str);
-  bco.num_workers = num_workers;
-  bco.decompress_ratio = folly::to<double>(decompress_ratio_str);
+  fsopts.lock_mode = parse_mlock_mode(lock_mode_str);
+  fsopts.block_cache.max_bytes = parse_size_with_unit(cache_size_str);
+  fsopts.block_cache.num_workers = num_workers;
+  fsopts.block_cache.decompress_ratio = folly::to<double>(decompress_ratio_str);
 
   dwarfs::filesystem_v2 fs(lgr, std::make_shared<dwarfs::mmap>(filesystem),
-                           bco);
+                           fsopts);
 
   worker_group wg("reader", num_readers);
 
diff --git a/test/dwarfs.cpp b/test/dwarfs.cpp
index e68dc532..9ebd602d 100644
--- a/test/dwarfs.cpp
+++ b/test/dwarfs.cpp
@@ -196,10 +196,10 @@ void basic_end_to_end_test(const std::string& compressor,
 
   auto mm = std::make_shared<test::mmap_mock>(oss.str());
 
-  block_cache_options bco;
-  bco.max_bytes = 1 << 20;
+  filesystem_options opts;
+  opts.block_cache.max_bytes = 1 << 20;
 
-  filesystem_v2 fs(lgr, mm, bco);
+  filesystem_v2 fs(lgr, mm, opts);
 
   auto entry = fs.find("/foo.pl");
   struct ::stat st;