TempleOSTS_140317.ISO

Demo/Lectures/Uncached.CPP

@@ -0,0 +1,55 @@
+#define SAMPLE_SIZE	100000
+
+U0 TimeIns()
+{
+  I64 i,start,end;
+  I64 *cached_I64=MAlloc(sizeof(I64)),
+     shared_blks,*uncached_I64;
+  CBlkPool *bp;
+  CHeapCtrl *hc;
+  Bool old_preempt;
+
+  "$$RED$$Now, this demo seems broken, perhaps,\n"
+  "because I run in a virtual machine.$$FG$$\n\n";
+  CPURep;
+
+  shared_blks=1;
+  bp=MemBlksUncachedAlloc(&shared_blks);
+  hc=HeapCtrlBPInit(bp,shared_blks<<12);
+  uncached_I64=MAlloc(sizeof(I64),hc);
+
+  old_preempt=Preempt(OFF);
+
+//Measure cached time
+  start=GetTSC;
+  for (i=0;i<SAMPLE_SIZE;i++)
+    *cached_I64=i;
+
+  end=GetTSC;
+  "  Cached Cycles: %10,d\n",end-start;
+
+//Measure uncached time
+  start=GetTSC;
+  for (i=0;i<SAMPLE_SIZE;i++)
+    *uncached_I64=i;
+  end=GetTSC;
+  "Uncached Cycles: %10,d\n",end-start;
+
+  "$$GREEN$$The difference is even greater\n"
+  "because the loop overhead was not subtracted.$$FG$$\n\n";
+  Free(cached_I64);
+  Free(uncached_I64);
+  MemBlks2MegFree(bp,shared_blks);
+  Preempt(old_preempt);
+}
+
+TimeIns;
+
+/*  Program Output$HL,0$$WW+H,1$$FD,1$
+
+8 Cores 2.660GHz
+  Cached Cycles:    202,220
+Uncached Cycles: 14,357,016
+$FG,2$The difference is even greater
+because the loop overhead was not subtracted.
+$HL,1$*/