Changeset 53142 in vbox for trunk/src/VBox/HostDrivers/Support

Timestamp:

Oct 24, 2014 2:03:12 PM (10 years ago)

Author:

vboxsync

svn:sync-xref-src-repo-rev:

96675

Message:

HostDrivers/support: Fix sign while applying TSC deltas, fix GIP timer update interval, fix premature commit of switching to sync TSC.

File:

• trunk/src/VBox/HostDrivers/Support/SUPDrv.c (modified) (7 diffs)

trunk/src/VBox/HostDrivers/Support/SUPDrv.c

@@ -5954 +5954 @@
             /*
              * Sleep wait since the TSC frequency is constant, eases host load.
+             * Shorter interval produces more variance in the frequency (esp. Windows).
              */
-#if 0
-            RTThreadSleep(98);
-            do
-            {
-                int64_t cNsWaited;
-                u64NanoTsAfter = RTTimeSystemNanoTS();
-                cNsWaited      = u64NanoTsAfter - u64NanoTs;
-                if (cNsWaited > RT_NS_100MS)
-                {
-                    uint64_t cNsBusyWait = RT_NS_1MS;
-                    for (;;)
-                    {
-                        u64NanoTsAfter = RTTimeSystemNanoTS();
-                        if (u64NanoTsAfter < cNsBusyWait + cNsWaited + u64NanoTs)
-                            ASMNopPause();
-                        else
-                            break;
-                    }
-                    break;
-                }
-            } while (1);
-#else
             RTThreadSleep(200);   /* Sleeping shorter produces a tad more variance in the frequency than I'd like. */
             u64NanoTsAfter = RTTimeSystemNanoTS();
@@ -5982 +5961 @@
                 ASMNopPause();
             u64NanoTsAfter = RTTimeSystemNanoTS();
-#endif
         }
         else
@@ -6018 +5996 @@
                 && pGipCpuAfter->i64TSCDelta  != INT64_MAX)
             {
-                u64TscBefore += pGipCpuBefore->i64TSCDelta;
-                u64TscAfter  += pGipCpuAfter->i64TSCDelta;
+                u64TscBefore -= pGipCpuBefore->i64TSCDelta;
+                u64TscAfter  -= pGipCpuAfter->i64TSCDelta;
 
                 SUPR0Printf("vboxdrv: TSC frequency is %lu Hz - invariant, kernel timer granularity is %lu Ns\n",
@@ -6094 +6072 @@
     /*
      * Find a reasonable update interval and initialize the structure.
-     *
-     * If we have an invariant TSC, use a larger update interval as then
-     * we get better accuracy along with lower host load.
-     */
-    u32MinInterval      = supdrvIsInvariantTsc() ? RT_NS_100MS : RT_NS_10MS;
+     */
+    /** @todo figure out why using a 100Ms interval upsets timekeeping in VMs.
+     *        See @bugref{6710}. */
+    u32MinInterval      = RT_NS_10MS;
     u32SystemResolution = RTTimerGetSystemGranularity();
     u32Interval         = u32MinInterval;
@@ -6279 +6256 @@
          */
         if (pGipCpu->i64TSCDelta != INT64_MAX)
-            u64TSC += pGipCpu->i64TSCDelta;
+            u64TSC -= pGipCpu->i64TSCDelta;
     }
 
@@ -7075 +7052 @@
 static SUPGIPMODE supdrvGipDeterminTscMode(PSUPDRVDEVEXT pDevExt)
 {
+#if 0
     if (supdrvIsInvariantTsc())
         return SUPGIPMODE_SYNC_TSC;     /** @todo Switch to SUPGIPMODE_INVARIANT_TSC later. */
+#endif
 
     /*
@@ -7341 +7320 @@
 
     /*
-     * For invariant TSC support, we take only 1 interval as there is a problem on
-     * Windows where we have an occasional (but reccurring) sour value that messes up
-     * the history. Also, since the update interval is pretty long with the invariant
-     * TSC case this works accurately enough.
-     */
-    if (supdrvIsInvariantTsc())
-    {
-        u32UpdateIntervalTSC = (uint32_t)u64TSCDelta;
-        u32UpdateIntervalTSCSlack = u32UpdateIntervalTSC >> 6;
-    }
-    /*
      * UpdateIntervalTSC = average of last 8,2,1 intervals depending on update HZ.
-     */
-    else if (pGip->u32UpdateHz >= 1000)
+     *
+     * On Windows, we have an occasional (but recurring) sour value that messed up
+     * the history but taking only 1 interval reduces the precision overall.
+     * However, this problem existed before the invariant mode was introduced.
+     */
+    if (   supdrvIsInvariantTsc()
+        || pGip->u32UpdateHz >= 1000)
     {
         uint32_t u32;