diff --git a/browser/app/nsBrowserApp.cpp b/browser/app/nsBrowserApp.cpp
index e663aecf0f70..8d96a3ee6a42 100644
--- a/browser/app/nsBrowserApp.cpp
+++ b/browser/app/nsBrowserApp.cpp
@@ -219,6 +219,10 @@ static int do_main(int argc, char* argv[], char* envp[]) {
 }
 
 static nsresult InitXPCOMGlue(LibLoadingStrategy aLibLoadingStrategy) {
+  if (gBootstrap) {
+    return NS_OK;
+  }
+
   UniqueFreePtr<char> exePath = BinaryPath::Get();
   if (!exePath) {
     Output("Couldn't find the application directory.\n");
@@ -243,6 +247,33 @@ uint32_t gBlocklistInitFlags = eDllBlocklistInitFlagDefault;
 #endif
 
 int main(int argc, char* argv[], char* envp[]) {
+#if defined(MOZ_ENABLE_FORKSERVER)
+  if (strcmp(argv[argc - 1], "forkserver") == 0) {
+    nsresult rv = InitXPCOMGlue(LibLoadingStrategy::NoReadAhead);
+    if (NS_FAILED(rv)) {
+      return 255;
+    }
+
+    // Run a fork server in this process, single thread.  When it
+    // returns, it means the fork server have been stopped or a new
+    // content process is created.
+    //
+    // For the later case, XRE_ForkServer() will return false, running
+    // in a content process just forked from the fork server process.
+    // argc & argv will be updated with the values passing from the
+    // chrome process.  With the new values, this function
+    // continues the reset of the code acting as a content process.
+    if(gBootstrap->XRE_ForkServer(&argc, &argv)) {
+      // Return from the fork server in the fork server process.
+      // Stop the fork server.
+      gBootstrap->NS_LogTerm();
+      return 0;
+    }
+    // In a content process forked from the fork server.
+    // Start acting as a content process.
+  }
+#endif
+
   mozilla::TimeStamp start = mozilla::TimeStamp::Now();
 
   AUTO_BASE_PROFILER_INIT;
diff --git a/ipc/app/MozillaRuntimeMain.cpp b/ipc/app/MozillaRuntimeMain.cpp
index b0a31cc23b0c..df61f8c47d13 100644
--- a/ipc/app/MozillaRuntimeMain.cpp
+++ b/ipc/app/MozillaRuntimeMain.cpp
@@ -13,18 +13,67 @@
 
 using namespace mozilla;
 
-int main(int argc, char* argv[]) {
-#ifdef HAS_DLL_BLOCKLIST
-  DllBlocklist_Initialize(eDllBlocklistInitFlagIsChildProcess);
+static bool
+UseForkServer(int argc, char* argv[]) {
+#if defined(MOZ_ENABLE_FORKSERVER)
+  return strcmp(argv[argc - 1], "forkserver") == 0;
+#else
+  return false;
 #endif
+}
 
+static int
+RunForkServer(Bootstrap::UniquePtr&& bootstrap, int argc, char* argv[]) {
+#if defined(MOZ_ENABLE_FORKSERVER)
+  int ret = 0;
+
+  bootstrap->NS_LogInit();
+
+  // Run a fork server in this process, single thread.  When it
+  // returns, it means the fork server have been stopped or a new
+  // content process is created.
+  //
+  // For the later case, XRE_ForkServer() will return false, running
+  // in a content process just forked from the fork server process.
+  // argc & argv will be updated with the values passing from the
+  // chrome process.  With the new values, this function
+  // continues the reset of the code acting as a content process.
+  if(bootstrap->XRE_ForkServer(&argc, &argv)) {
+    // Return from the fork server in the fork server process.
+    // Stop the fork server.
+  } else {
+    // In a content process forked from the fork server.
+    // Start acting as a content process.
+    ret = content_process_main(bootstrap.get(), argc, argv);
+  }
+
+  bootstrap->NS_LogTerm();
+  return ret;
+#else
+  return 0;
+#endif
+}
+
+int main(int argc, char* argv[]) {
   Bootstrap::UniquePtr bootstrap = GetBootstrap();
   if (!bootstrap) {
     return 2;
   }
-  int ret = content_process_main(bootstrap.get(), argc, argv);
-#if defined(DEBUG) && defined(HAS_DLL_BLOCKLIST)
-  DllBlocklist_Shutdown();
+
+  int ret;
+  if (UseForkServer(argc, argv)) {
+    ret = RunForkServer(std::move(bootstrap), argc, argv);
+  } else {
+#ifdef HAS_DLL_BLOCKLIST
+    DllBlocklist_Initialize(eDllBlocklistInitFlagIsChildProcess);
 #endif
+
+    ret = content_process_main(bootstrap.get(), argc, argv);
+
+#if defined(DEBUG) && defined(HAS_DLL_BLOCKLIST)
+    DllBlocklist_Shutdown();
+#endif
+  }
+
   return ret;
 }
diff --git a/ipc/chromium/src/base/process_util_linux.cc b/ipc/chromium/src/base/process_util_linux.cc
index ea2b1edc34ac..0132072025cb 100644
--- a/ipc/chromium/src/base/process_util_linux.cc
+++ b/ipc/chromium/src/base/process_util_linux.cc
@@ -162,14 +162,32 @@ handle_sigchld(int s) {
   waitpid(-1, nullptr, WNOHANG);
 }
 
-void
-InitForkServerProcess() {
+static void
+InstallChildSignalHandler() {
   // Since content processes are not children of the chrome process
   // any more, the fork server process has to handle SIGCHLD, or
   // content process would remain zombie after dead.
   signal(SIGCHLD, handle_sigchld);
 }
 
+static void
+ReserveFileDescriptors() {
+  // Reserve the lower positions of the file descriptors to make sure
+  // debug files and other files don't take these positions.  So we
+  // can keep their file descriptors during CloseSuperfluousFds() with
+  // out any confliction with mapping passing from the parent process.
+  int fd = open("/dev/null", O_RDONLY);
+  for (int i = 1; i < 10; i++) {
+    dup(fd);
+  }
+}
+
+void
+InitForkServerProcess() {
+  InstallChildSignalHandler();
+  ReserveFileDescriptors();
+}
+
 static bool
 LaunchAppWithForkServer(const std::vector<std::string>& argv,
                       const LaunchOptions& options,
diff --git a/ipc/glue/ForkServer.cpp b/ipc/glue/ForkServer.cpp
index caf85f0bb0f8..18b2f770e482 100644
--- a/ipc/glue/ForkServer.cpp
+++ b/ipc/glue/ForkServer.cpp
@@ -300,6 +300,9 @@ ForkServer::RunForkServer(int* aArgc, char*** aArgv) {
     forkserver.mAppProcBuilder->InitAppProcess(aArgc, aArgv);
     forkserver.mAppProcBuilder.reset();
 
+    // Open log files again with the right names with the new PID.
+    nsTraceRefcnt::ResetLogFiles();
+
     return false;
 }
 
diff --git a/ipc/glue/ForkServiceChild.cpp b/ipc/glue/ForkServiceChild.cpp
index d148cc1127e2..071b77f4051d 100644
--- a/ipc/glue/ForkServiceChild.cpp
+++ b/ipc/glue/ForkServiceChild.cpp
@@ -112,5 +112,45 @@ ForkServiceChild::OnMessageReceived(IPC::Message&& message) {
     message.EndRead(iter__, message.type());
 }
 
+NS_IMPL_ISUPPORTS(ForkServerLauncher, nsIObserver)
+
+bool ForkServerLauncher::mHaveStartedClient = false;
+StaticRefPtr<ForkServerLauncher> ForkServerLauncher::mSingleton;
+
+ForkServerLauncher::ForkServerLauncher() {
+}
+
+ForkServerLauncher::~ForkServerLauncher() {
+}
+
+already_AddRefed<ForkServerLauncher>
+ForkServerLauncher::Create() {
+    if (mSingleton == nullptr) {
+        mSingleton = new ForkServerLauncher();
+    }
+    RefPtr<ForkServerLauncher> launcher = mSingleton;
+    return launcher.forget();
+}
+
+NS_IMETHODIMP
+ForkServerLauncher::Observe(nsISupports* aSubject,
+                           const char* aTopic,
+                           const char16_t* aData) {
+    if (!mHaveStartedClient && strcmp(aTopic, NS_XPCOM_STARTUP_CATEGORY) == 0) {
+        mHaveStartedClient = true;
+        ForkServiceChild::StartForkServer();
+
+        nsCOMPtr<nsIObserverService> obsSvc = mozilla::services::GetObserverService();
+        MOZ_ASSERT(obsSvc != nullptr);
+        obsSvc->AddObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID, false);
+    }
+
+    if (mHaveStartedClient && strcmp(aTopic, NS_XPCOM_SHUTDOWN_OBSERVER_ID) == 0) {
+        mHaveStartedClient = false;
+        ForkServiceChild::StopForkServer();
+    }
+    return NS_OK;
+}
+
 }
 }
diff --git a/ipc/glue/ForkServiceChild.h b/ipc/glue/ForkServiceChild.h
index 7a8ed5a429c5..362e08803c1b 100644
--- a/ipc/glue/ForkServiceChild.h
+++ b/ipc/glue/ForkServiceChild.h
@@ -73,6 +73,24 @@ private:
     GeckoChildProcessHost* mProcess;
 };
 
+/**
+ * Start a fork server at |xpcom-startup| from the chrome process.
+ */
+class ForkServerLauncher : public nsIObserver {
+public:
+    NS_DECL_ISUPPORTS
+    NS_DECL_NSIOBSERVER
+
+    ForkServerLauncher();
+    static already_AddRefed<ForkServerLauncher> Create();
+
+private:
+    virtual ~ForkServerLauncher();
+
+    static bool mHaveStartedClient;
+    static StaticRefPtr<ForkServerLauncher> mSingleton;
+};
+
 }
 }
 
diff --git a/ipc/glue/components.conf b/ipc/glue/components.conf
new file mode 100644
index 000000000000..34048dbbfa20
--- /dev/null
+++ b/ipc/glue/components.conf
@@ -0,0 +1,22 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+Headers = [
+    'mozilla/ipc/ForkServer.h',
+]
+
+Classes = [
+    {
+        'cid': '{cdb4757f-f51b-40c0-8b38-66d12c3bff7b}',
+        'contract_ids': ['@mozilla.org/fork-server-launcher;1'],
+        'singleton': True,
+        'type': 'mozilla::ipc::ForkServerLauncher',
+        'headers': ['mozilla/ipc/ForkServiceChild.h'],
+        'constructor': 'mozilla::ipc::ForkServerLauncher::Create',
+        'processes': ProcessSelector.MAIN_PROCESS_ONLY,
+        'categories': {'xpcom-startup': 'Fork Server Launcher'},
+    },
+]
diff --git a/ipc/glue/moz.build b/ipc/glue/moz.build
index 2b48dd8ff6e9..68a08a597e1b 100644
--- a/ipc/glue/moz.build
+++ b/ipc/glue/moz.build
@@ -231,6 +231,9 @@ if CONFIG['MOZ_ENABLE_FORKSERVER']:
         'ForkServiceChild.cpp',
         'MiniTransceiver.cpp',
     ]
+    XPCOM_MANIFESTS += [
+        'components.conf',
+    ]
 
 LOCAL_INCLUDES += [
     '/dom/ipc',
diff --git a/moz.configure b/moz.configure
index 5e5c8ddcb1ba..58d2e03793f1 100755
--- a/moz.configure
+++ b/moz.configure
@@ -634,6 +634,19 @@ llvm_objdump = check_prog('LLVM_OBJDUMP', llvm_objdump, what='llvm-objdump',
 
 add_old_configure_assignment('LLVM_OBJDUMP', llvm_objdump)
 
+# Fork server
+option('--enable-forkserver', env='MOZ_ENABLE_FORKSERVER', help='Enable fork server')
+
+@depends('--enable-forkserver', target)
+def forkserver_flag(value, target):
+    if target.os == 'Android' or \
+       (target.os == 'GNU' and target.kernel == 'Linux'):
+        return bool(value)
+    pass
+
+set_config('MOZ_ENABLE_FORKSERVER', forkserver_flag)
+set_define('MOZ_ENABLE_FORKSERVER', forkserver_flag, forkserver_flag)
+
 
 # Please do not add configure checks from here on.
 
diff --git a/toolkit/xre/Bootstrap.cpp b/toolkit/xre/Bootstrap.cpp
index 9d7cb8f41977..cc6d30c8d06f 100644
--- a/toolkit/xre/Bootstrap.cpp
+++ b/toolkit/xre/Bootstrap.cpp
@@ -102,6 +102,12 @@ class BootstrapImpl final : public Bootstrap {
     return ::XRE_RunIPDLTest(argc, argv);
   }
 #endif
+
+#ifdef MOZ_ENABLE_FORKSERVER
+  virtual int XRE_ForkServer(int* argc, char*** argv) override {
+    return ::XRE_ForkServer(argc, argv);
+  }
+#endif
 };
 
 extern "C" NS_EXPORT void NS_FROZENCALL
diff --git a/toolkit/xre/Bootstrap.h b/toolkit/xre/Bootstrap.h
index 7ef9185a9fe9..af6840e646e0 100644
--- a/toolkit/xre/Bootstrap.h
+++ b/toolkit/xre/Bootstrap.h
@@ -126,6 +126,10 @@ class Bootstrap {
 #ifdef MOZ_IPDL_TESTS
   virtual int XRE_RunIPDLTest(int argc, char** argv) = 0;
 #endif
+
+#ifdef MOZ_ENABLE_FORKSERVER
+  virtual int XRE_ForkServer(int* argc, char*** argv) = 0;
+#endif
 };
 
 enum class LibLoadingStrategy {
diff --git a/toolkit/xre/nsEmbedFunctions.cpp b/toolkit/xre/nsEmbedFunctions.cpp
index 942f98a53b78..e74ea0de0c8f 100644
--- a/toolkit/xre/nsEmbedFunctions.cpp
+++ b/toolkit/xre/nsEmbedFunctions.cpp
@@ -133,6 +133,10 @@ using mozilla::_ipdltest::IPDLUnitTestProcessChild;
 #  include "mozilla/sandboxing/sandboxLogging.h"
 #endif
 
+#if defined(MOZ_ENABLE_FORKSERVER)
+#  include "mozilla/ipc/ForkServer.h"
+#endif
+
 #include "VRProcessChild.h"
 
 using namespace mozilla;
@@ -264,7 +268,8 @@ void XRE_SetAndroidChildFds(JNIEnv* env, const XRE_AndroidChildFds& fds) {
 
 void XRE_SetProcessType(const char* aProcessTypeString) {
   static bool called = false;
-  if (called) {
+  if (called &&
+      sChildProcessType != GeckoProcessType_ForkServer) {
     MOZ_CRASH();
   }
   called = true;
@@ -730,6 +735,12 @@ nsresult XRE_InitChildProcess(int aArgc, char* aArgv[],
           process = new RemoteSandboxBrokerProcessChild(parentPID);
           break;
 #endif
+
+#if defined(MOZ_ENABLE_FORKSERVER)
+        case GeckoProcessType_ForkServer:
+          MOZ_CRASH("Fork server should not go here");
+          break;
+#endif
         default:
           MOZ_CRASH("Unknown main thread class");
       }
@@ -1025,3 +1036,9 @@ void XRE_InstallX11ErrorHandler() {
 #  endif
 }
 #endif
+
+#ifdef MOZ_ENABLE_FORKSERVER
+int XRE_ForkServer(int* aArgc, char*** aArgv) {
+  return mozilla::ipc::ForkServer::RunForkServer(aArgc, aArgv) ? 1 : 0;
+}
+#endif
diff --git a/xpcom/base/Logging.cpp b/xpcom/base/Logging.cpp
index 5e822d3aefb1..358b21ba29c8 100644
--- a/xpcom/base/Logging.cpp
+++ b/xpcom/base/Logging.cpp
@@ -377,8 +377,7 @@ class LogModuleManager {
 
   void Print(const char* aName, LogLevel aLevel, const char* aFmt,
              va_list aArgs) MOZ_FORMAT_PRINTF(4, 0) {
-    // We don't do nuwa-style forking anymore, so our pid can't change.
-    static long pid = static_cast<long>(base::GetCurrentProcId());
+    long pid = static_cast<long>(base::GetCurrentProcId());
     const size_t kBuffSize = 1024;
     char buff[kBuffSize];
 
diff --git a/xpcom/base/nsTraceRefcnt.cpp b/xpcom/base/nsTraceRefcnt.cpp
index f9357e89c749..aef1b2d2b11d 100644
--- a/xpcom/base/nsTraceRefcnt.cpp
+++ b/xpcom/base/nsTraceRefcnt.cpp
@@ -523,6 +523,9 @@ static bool InitLog(const EnvCharType* aEnvVar, const char* aMsg,
 #endif
       if (stream) {
         MozillaRegisterDebugFD(fileno(stream));
+#ifdef MOZ_ENABLE_FORKSERVER
+        base::RegisterForkServerNoCloseFD(fileno(stream));
+#endif
         *aResult = stream;
         fprintf(stderr,
                 "### " ENVVAR_PRINTF " defined -- logging %s to " ENVVAR_PRINTF
@@ -1157,3 +1160,32 @@ void nsTraceRefcnt::SetActivityIsLegal(bool aLegal) {
 
   PR_SetThreadPrivate(gActivityTLS, reinterpret_cast<void*>(!aLegal));
 }
+
+#ifdef MOZ_ENABLE_FORKSERVER
+void nsTraceRefcnt::ResetLogFiles() {
+#ifdef XP_WIN
+#  define ENVVAR(x) u"" x
+#else
+#  define ENVVAR(x) x
+#endif
+  if (gBloatLog) {
+    maybeUnregisterAndCloseFile(gBloatLog);
+    bool defined = InitLog(ENVVAR("XPCOM_MEM_BLOAT_LOG"), "bloat/leaks", &gBloatLog);
+    if (!defined) {
+      InitLog(ENVVAR("XPCOM_MEM_LEAK_LOG"), "leaks", &gBloatLog);
+    }
+  }
+  if (gRefcntsLog) {
+    maybeUnregisterAndCloseFile(gRefcntsLog);
+    InitLog(ENVVAR("XPCOM_MEM_REFCNT_LOG"), "refcounts", &gRefcntsLog);
+  }
+  if (gAllocLog) {
+    maybeUnregisterAndCloseFile(gAllocLog);
+    InitLog(ENVVAR("XPCOM_MEM_ALLOC_LOG"), "new/delete", &gAllocLog);
+  }
+  if(gCOMPtrLog) {
+    maybeUnregisterAndCloseFile(gCOMPtrLog);
+    InitLog(ENVVAR("XPCOM_MEM_COMPTR_LOG"), "nsCOMPtr", &gCOMPtrLog);
+  }
+}
+#endif
diff --git a/xpcom/base/nsTraceRefcnt.h b/xpcom/base/nsTraceRefcnt.h
index 1516e9ab1a2e..35d142c4b643 100644
--- a/xpcom/base/nsTraceRefcnt.h
+++ b/xpcom/base/nsTraceRefcnt.h
@@ -28,6 +28,10 @@ class nsTraceRefcnt {
    * activity that occurs because of static constructors or destructors.
    */
   static void SetActivityIsLegal(bool aLegal);
+
+#ifdef MOZ_ENABLE_FORKSERVER
+  static void ResetLogFiles();
+#endif
 };
 
 #endif  // nsTraceRefcnt_h
diff --git a/xpcom/build/nsXULAppAPI.h b/xpcom/build/nsXULAppAPI.h
index 6712c36a6fe0..a82f0ac62be4 100644
--- a/xpcom/build/nsXULAppAPI.h
+++ b/xpcom/build/nsXULAppAPI.h
@@ -509,4 +509,10 @@ XRE_API(void, XRE_LibFuzzerSetDriver, (LibFuzzerDriver))
 
 #endif  // LIBFUZZER
 
+#ifdef MOZ_ENABLE_FORKSERVER
+
+XRE_API(int, XRE_ForkServer, (int* aArgc, char*** aArgv))
+
+#endif // MOZ_ENABLE_FORKSERVER
+
 #endif  // _nsXULAppAPI_h__