new acoEventFD option (on Linux only)

- will use eventfd() instead of futexes to notify the processing threads
- by design, will disable acoThreadSmooting
- numbers on regular HW (laptop) are not better, but it may help on high-end HW with a lot of cores (let's test it) :)

Author: Arnaud Bouchez

src/mormot.commit.inc

@@ -1 +1 @@
-'2.0.4977'
+'2.0.4978'

src/net/mormot.net.async.pas

@@ -471,6 +471,8 @@   TAsyncConnectionsThread = class(TSynThread)
   // - acoThreadSmooting will change the ThreadPollingWakeup() algorithm to
   // focus the process on the first threads of the pool - by design, this
   // setting will disable both acoThreadCpuAffinity and acoThreadSocketAffinity
+  // - acoEventFD (on Linux only) will use eventfd() instead of futexes to
+  // notify the processing threads - by design, will disable acoThreadSmooting
   TAsyncConnectionsOptions = set of (
     acoOnErrorContinue,
     acoNoLogRead,
@@ -483,7 +485,8 @@   TAsyncConnectionsThread = class(TSynThread)
     acoThreadCpuAffinity,
     acoThreadSocketAffinity,
     acoReusePort,
-    acoThreadSmooting
+    acoThreadSmooting,
+    acoEventFD
   );
 
   /// to implement generational garbage collector of asynchronous connections
@@ -1843,10 +1846,7 @@ procedure TAsyncConnectionsThread.Execute;
                 //fOwner.fClients.fRead.PendingLogDebug('Wakeup');
                 fEvent.ResetEvent;
                 fWaitForReadPending := true; // should be set before wakeup
-                if Assigned(fOwner.fThreadPollingEventFD) then
-                  fOwner.fThreadPollingEventFD.SetEvent(new)
-                else
-                  fOwner.ThreadPollingWakeup(pending);
+                fOwner.ThreadPollingWakeup(new);
                 //fOwner.DoLog(sllCustom1, 'Execute: WaitFor ReadPending', [], self);
                 if not Terminated then
                   fEvent.WaitFor(20);
@@ -1978,7 +1978,8 @@ constructor TAsyncConnections.Create(const OnStart, OnStop: TOnNotifyThread;
   // prepare this main thread: fThreads[] requires proper fOwner.OnStart/OnStop
   inherited Create({suspended=}false, OnStart, OnStop, ProcessName);
   // initiate the read/receive thread(s)
-  // fThreadPollingEventFD := NewEventFD; // nil if unsupported
+  if acoEventFD in aOptions then
+    fThreadPollingEventFD := NewEventFD; // nil if unsupported
   fThreadPoolCount := aThreadPoolCount;
   SetLength(fThreads, fThreadPoolCount);
   if aThreadPoolCount = 1 then
@@ -3528,7 +3529,10 @@ constructor THttpAsyncServer.Create(const aPort: RawUtf8;
   //include(aco, acoWritePollOnly);
   if hsoEnableTls in ProcessOptions then
     include(aco, acoEnableTls);
-  if hsoThreadSmooting in ProcessOptions then
+  if (hsoEventFD in ProcessOptions) and
+     (NewEventFD <> nil) then // try to allocate a temporary eventfd() instance
+    include(aco, acoEventFD)        // and exclude other options
+  else if hsoThreadSmooting in ProcessOptions then
     include(aco, acoThreadSmooting) // and exclude any thread affinity
   else
   begin

src/net/mormot.net.server.pas

@@ -343,6 +343,8 @@   THttpServerRequest = class(THttpServerRequestAbstract)
   // - hsoThreadSmooting will change the TAsyncConnections.ThreadPollingWakeup()
   // algorithm to focus the process on the first threads of the pool - by design,
   // this will disable both hsoThreadCpuAffinity and hsoThreadSocketAffinity
+  // - hsoEventFD (on Linux only) will use eventfd() instead of futexes to
+  // notify the TAsyncConnections threads - by design, disable acoThreadSmooting
   THttpServerOption = (
     hsoHeadersUnfiltered,
     hsoHeadersInterning,
@@ -356,7 +358,8 @@   THttpServerRequest = class(THttpServerRequestAbstract)
     hsoThreadCpuAffinity,
     hsoThreadSocketAffinity,
     hsoReusePort,
-    hsoThreadSmooting);
+    hsoThreadSmooting,
+    hsoEventFD);
 
   /// how a THttpServerGeneric class is expected to process incoming requests
   THttpServerOptions = set of THttpServerOption;

src/net/mormot.net.sock.posix.inc

@@ -1214,7 +1214,7 @@ const
   // exists since Kernel 2.6.27
   syscall_nr_eventfd2 = 290;
   // = 328 on i386
-  // = 356 on AARM64
+  // = 356 on AARCH64
 
 function eventfd(initval, flags: cardinal): integer; inline;
 begin