Add ability to set readahead of mergerfs and branches

README.md

@@ -211,6 +211,8 @@ These options are the same regardless of whether you use them with the
 * **rename-exdev=passthrough|rel-symlink|abs-symlink**: When a rename
   fails with EXDEV optionally move the file to a special directory and
   symlink to it.
+* **readahead=UINT**: Set readahead (in kilobytes) for mergerfs and
+  branches if greater than 0. (default: 0)
 * **posix_acl=BOOL**: Enable POSIX ACL support (if supported by kernel
   and underlying filesystem). (default: false)
 * **async_read=BOOL**: Perform reads asynchronously. If disabled or
@@ -1528,8 +1530,7 @@ understand what behaviors it may impact
 * use `symlinkify` if your data is largely static and read-only
 * use tiered cache drives
 * use LVM and LVM cache to place a SSD in front of your HDDs
-* if `cache.files` is enabled increase readahead: `echo "1024" > /sys/class/bdi/0:$(stat -c%d /MOUNT)/read_ahead_kb`
-* increase readahead on all devices: `ls -1 /sys/class/bdi/*/read_ahead_kb | xargs -n1 -I{} sh -c "echo 1024 > {}"`
+* increase readahead: `readahead=1024`
 
 If you come across a setting that significantly impacts performance
 please contact trapexit so he may investigate further. Please test

man/mergerfs.1

@@ -265,6 +265,10 @@ instead.
 rename fails with EXDEV optionally move the file to a special directory
 and symlink to it.
 .IP \[bu] 2
+\f[B]readahead=UINT\f[R]: Set readahead (in kilobytes) for mergerfs and
+branches if greater than 0.
+(default: 0)
+.IP \[bu] 2
 \f[B]posix_acl=BOOL\f[R]: Enable POSIX ACL support (if supported by
 kernel and underlying filesystem).
 (default: false)
@@ -1982,11 +1986,7 @@ use tiered cache drives
 .IP \[bu] 2
 use LVM and LVM cache to place a SSD in front of your HDDs
 .IP \[bu] 2
-if \f[C]cache.files\f[R] is enabled increase readahead:
-\f[C]echo \[dq]1024\[dq] > /sys/class/bdi/0:$(stat -c%d /MOUNT)/read_ahead_kb\f[R]
-.IP \[bu] 2
-increase readahead on all devices:
-\f[C]ls -1 /sys/class/bdi/*/read_ahead_kb | xargs -n1 -I{} sh -c \[dq]echo 1024 > {}\[dq]\f[R]
+increase readahead: \f[C]readahead=1024\f[R]
 .PP
 If you come across a setting that significantly impacts performance
 please contact trapexit so he may investigate further.

src/config.cpp

@@ -105,6 +105,7 @@ Config::Config()
     nullrw(false),
     pid(::getpid()),
     posix_acl(false),
+    readahead(0),
     readdir(ReadDir::ENUM::POSIX),
     readdirplus(false),
     rename_exdev(RenameEXDEV::ENUM::PASSTHROUGH),
@@ -176,6 +177,7 @@ Config::Config()
   _map["nullrw"]                 = &nullrw;
   _map["pid"]                    = &pid;
   _map["posix_acl"]              = &posix_acl;
+  _map["readahead"]              = &readahead;
   //  _map["readdir"]            = &readdir;
   _map["readdirplus"]            = &readdirplus;
   _map["rename-exdev"]           = &rename_exdev;

src/config.hpp

@@ -133,6 +133,7 @@ public:
   ConfigBOOL     nullrw;
   ConfigUINT64   pid;
   ConfigBOOL     posix_acl;
+  ConfigUINT64   readahead;
   ReadDir        readdir;
   ConfigBOOL     readdirplus;
   RenameEXDEV    rename_exdev;

src/fs_readahead.cpp

@@ -0,0 +1,86 @@
+/*
+  ISC License
+
+  Copyright (c) 2023, Antonio SJ Musumeci <trapexit@spawn.link>
+
+  Permission to use, copy, modify, and/or distribute this software for any
+  purpose with or without fee is hereby granted, provided that the above
+  copyright notice and this permission notice appear in all copies.
+
+  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+
+#include "fs_readahead.hpp"
+
+#include "fmt/core.h"
+#include "fs_lstat.hpp"
+
+#include <cstdint>
+#include <fstream>
+#include <string>
+
+#include <sys/sysmacros.h>
+
+namespace l
+{
+  static
+  std::string
+  generate_readahead_sys_path(const std::uint64_t major_,
+                              const std::uint64_t minor_)
+  {
+    return fmt::format("/sys/class/bdi/{}:{}/read_ahead_kb",major_,minor_);
+  }
+}
+
+int
+fs::readahead(const std::uint64_t major_dev_,
+              const std::uint64_t minor_dev_,
+              const std::uint64_t size_in_kb_)
+{
+  std::string syspath;
+  std::ofstream ofs;
+
+  syspath = l::generate_readahead_sys_path(major_dev_,minor_dev_);
+
+  ofs.open(syspath);
+  if(ofs)
+    {
+      ofs << fmt::format("{}\n",size_in_kb_);
+      ofs.close();
+    }
+
+  return 0;
+}
+
+int
+fs::readahead(const std::uint64_t dev_,
+              const std::uint64_t size_in_kb_)
+{
+  std::uint32_t major_dev;
+  std::uint32_t minor_dev;
+
+  major_dev = major(dev_);
+  minor_dev = minor(dev_);
+
+  return fs::readahead(major_dev,minor_dev,size_in_kb_);
+}
+
+int
+fs::readahead(const std::string   path_,
+              const std::uint64_t size_in_kb_)
+{
+  int rv;
+  struct stat st;
+
+  rv = fs::lstat(path_,&st);
+  if(rv == -1)
+    return -errno;
+
+  return fs::readahead(st.st_dev,size_in_kb_);
+}

src/fs_readahead.hpp

@@ -0,0 +1,39 @@
+/*
+  ISC License
+
+  Copyright (c) 2023, Antonio SJ Musumeci <trapexit@spawn.link>
+
+  Permission to use, copy, modify, and/or distribute this software for any
+  purpose with or without fee is hereby granted, provided that the above
+  copyright notice and this permission notice appear in all copies.
+
+  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+
+#pragma once
+
+#include <cstdint>
+#include <string>
+
+
+namespace fs
+{
+  int
+  readahead(const std::uint64_t major_dev,
+            const std::uint64_t minor_dev,
+            const std::uint64_t size_in_kb);
+
+  int
+  readahead(const std::uint64_t dev,
+            const std::uint64_t size_in_kb);
+
+  int
+  readahead(const std::string   path,
+            const std::uint64_t size_in_kb);
+}

src/fuse_init.cpp

@@ -16,9 +16,15 @@
 
 #include "config.hpp"
 #include "ugid.hpp"
+#include "fs_readahead.hpp"
+#include "syslog.hpp"
+
+#include "fmt/core.h"
 
 #include "fuse.h"
 
+#include <thread>
+
 
 namespace l
 {
@@ -77,6 +83,49 @@ namespace l
         cfg_->fuse_msg_size = FUSE_DEFAULT_MAX_PAGES_PER_REQ;
       }
   }
+
+  static
+  void
+  readahead(const std::string path_,
+            const int         readahead_)
+  {
+    int rv;
+
+    rv = fs::readahead(path_,readahead_);
+    if(rv == 0)
+      syslog_info("%s - readahead set to %d",path_.c_str(),readahead_);
+    else
+      syslog_error("%s - unable to set readahead",path_.c_str());
+  }
+
+  static
+  void
+  set_readahead_on_mount_and_branches()
+  {
+    Config::Read cfg;
+    Branches::CPtr branches;
+
+    if((uint64_t)cfg->readahead == 0)
+      return;
+
+    l::readahead(cfg->mountpoint,cfg->readahead);
+
+    branches = cfg->branches;
+    for(auto const &branch : *branches)
+      l::readahead(branch.path,cfg->readahead);
+  }
+
+  // Spawn a thread to do this because before init returns calls to
+  // set the value will block leading to a deadlock. This is just
+  // easier.
+  static
+  void
+  spawn_thread_to_set_readahead()
+  {
+    std::thread readahead_thread(l::set_readahead_on_mount_and_branches);
+
+    readahead_thread.detach();
+  }
 }
 
 namespace FUSE
@@ -104,6 +153,8 @@ namespace FUSE
     conn_->want &= ~FUSE_CAP_POSIX_LOCKS;
     conn_->want &= ~FUSE_CAP_FLOCK_LOCKS;
 
+    l::spawn_thread_to_set_readahead();
+
     return NULL;
   }
 }

src/mergerfs.cpp

@@ -14,6 +14,7 @@
   OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
 
+#include "fs_readahead.hpp"
 #include "fs_wait_for_mount.hpp"
 #include "syslog.hpp"