Allow setting of scheduling priority

README.md

@@ -1,6 +1,6 @@
 % mergerfs(1) mergerfs user manual
 % Antonio SJ Musumeci <trapexit@spawn.link>
-% 2023-01-24
+% 2023-01-25
 
 # NAME
 
@@ -203,6 +203,9 @@ These options are the same regardless of whether you use them with the `mergerfs
   `read-thread-count` refers to the number of threads reading FUSE
   messages which are dispatched to process threads. -1 means disabled
   otherwise acts like `read-thread-count`. (default: -1)
+* **scheduling-priority=INT**: Set mergerfs' scheduling
+  priority. Valid values range from -20 to 19. See `setpriority` man
+  page for more details. (default: -10)
 * **fsname=STR**: Sets the name of the filesystem as seen in
   **mount**, **df**, etc. Defaults to a list of the source paths
   concatenated together with the longest common prefix removed.

src/config.cpp

@@ -64,6 +64,7 @@ namespace l
     IFERT("readdirplus");
     IFERT("threads");
     IFERT("version");
+    IFERT("scheduling-priority");
 
     return false;
   }
@@ -103,6 +104,7 @@ Config::Config()
     readdir(ReadDir::ENUM::POSIX),
     readdirplus(false),
     rename_exdev(RenameEXDEV::ENUM::PASSTHROUGH),
+    scheduling_priority(-10),
     security_capability(true),
     srcmounts(branches),
     statfs(StatFS::ENUM::BASE),
@@ -171,6 +173,7 @@ Config::Config()
   //  _map["readdir"]            = &readdir;
   _map["readdirplus"]            = &readdirplus;
   _map["rename-exdev"]           = &rename_exdev;
+  _map["scheduling-priority"]    = &scheduling_priority;
   _map["security_capability"]    = &security_capability;
   _map["srcmounts"]              = &srcmounts;
   _map["statfs"]                 = &statfs;

src/config.hpp

@@ -133,6 +133,7 @@ public:
   ReadDir        readdir;
   ConfigBOOL     readdirplus;
   RenameEXDEV    rename_exdev;
+  ConfigINT      scheduling_priority;
   ConfigBOOL     security_capability;
   SrcMounts      srcmounts;
   StatFS         statfs;
@@ -145,6 +146,7 @@ public:
   ConfigBOOL     writeback_cache;
   XAttr          xattr;
 
+
 public:
   friend std::ostream& operator<<(std::ostream &s,
                                   const Config &c);

src/mergerfs.cpp

@@ -139,15 +139,13 @@ namespace l
 
   static
   void
-  setup_resources(void)
+  setup_resources(const int scheduling_priority_)
   {
-    const int prio = -10;
-
     std::srand(time(NULL));
     resources::reset_umask();
     resources::maxout_rlimit_nofile();
     resources::maxout_rlimit_fsize();
-    resources::setpriority(prio);
+    resources::setpriority(scheduling_priority_);
   }
 
   static
@@ -204,7 +202,7 @@ namespace l
     if(cfg->branches_mount_timeout > 0)
       l::wait_for_mount(cfg);
 
-    l::setup_resources();
+    l::setup_resources(cfg->scheduling_priority);
     l::get_fuse_operations(ops,cfg->nullrw);
 
     return fuse_main(args.argc,