[client] added 1ms delay loop for incoming polling support

client/Makefile

@@ -13,6 +13,7 @@ BUILD   ?= .build
 BIN     ?= bin
 
 OBJS	= main.o \
+	  delay.o \
 	  spice/spice.o \
 	  ivshmem/ivshmem.o \
 	  renderers/basic.o \

client/delay.c

@@ -0,0 +1,70 @@
+/*
+Looking Glass - KVM FrameRelay (KVMFR) Client
+Copyright (C) 2017 Geoffrey McRae <geoff@hostfission.com>
+
+This program is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation; either version 2 of the License, or (at your option) any later
+version.
+
+This program is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+this program; if not, write to the Free Software Foundation, Inc., 59 Temple
+Place, Suite 330, Boston, MA 02111-1307 USA
+*/
+
+#include "delay.h"
+
+#include <SDL2/SDL.h>
+
+#include "debug.h"
+
+static unsigned int delay_loop_count = 0;
+
+void delay()
+{
+  unsigned char j;
+  for(unsigned int i = 0; i < delay_loop_count; ++i)
+  {
+    j = 0;
+    while(--j)
+      asm("");
+  }
+}
+
+void delay_calibrate()
+{
+  // initialize the poll limit to a sane value
+  for(int start = SDL_GetTicks(); SDL_GetTicks() - start < 10; ++delay_loop_count) {}
+  DEBUG_INFO("Init : %u", delay_loop_count);
+
+  // the following loop must produce 20 concurrent valid results to ensure a valid calculation
+  int okCount = 0;
+  while(okCount < 20)
+  {
+    // time the final loop and calculate the remaining time
+    unsigned int ticks = SDL_GetTicks();
+    delay();
+    int remain = 10 - (SDL_GetTicks() - ticks);
+
+    // if the remaining time is within 2ms, accept it (Linux is not a RTOS)
+    if (remain > -2 && remain < 2)
+    {
+      ++okCount;
+      continue;
+    }
+
+    // the delay is out of spec, adjust the limit
+    okCount = 0;
+    DEBUG_INFO("Diff : %c%d ms", remain > 0 ? '-' : '+', abs(remain));
+    delay_loop_count += ceil(((double)delay_loop_count / 10.0) * remain);
+  }
+
+  DEBUG_INFO("Final: %u", delay_loop_count);
+
+  // scale the limit for a 1ms delay
+  delay_loop_count = ceil((double)delay_loop_count / 10.0);
+}

client/delay.h

@@ -0,0 +1,22 @@
+/*
+Looking Glass - KVM FrameRelay (KVMFR) Client
+Copyright (C) 2017 Geoffrey McRae <geoff@hostfission.com>
+
+This program is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation; either version 2 of the License, or (at your option) any later
+version.
+
+This program is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+this program; if not, write to the Free Software Foundation, Inc., 59 Temple
+Place, Suite 330, Boston, MA 02111-1307 USA
+*/
+
+#pragma once
+
+void delay_calibrate();
+void delay();

client/main.c

@@ -34,6 +34,7 @@ Place, Suite 330, Boston, MA 02111-1307 USA
 #include <GL/glu.h>
 
 #include "debug.h"
+#include "delay.h"
 #include "memcpySSE.h"
 #include "KVMFR.h"
 #include "ivshmem/ivshmem.h"
@@ -641,6 +642,8 @@ int run()
   state.scaleX  = 1.0f;
   state.scaleY  = 1.0f;
 
+  delay_calibrate();
+
   if (SDL_Init(SDL_INIT_VIDEO) < 0)
   {
     DEBUG_ERROR("SDL_Init Failed");