Changeset 87749 in vbox

Timestamp:

Feb 13, 2021 3:18:27 AM (4 years ago)

Author:

vboxsync

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

142801

Message:

VMM/TM: Relax ordering when signaling update-in-progress in TMNotifyEndOfExecution. bugref:9941

File:

• trunk/src/VBox/VMM/VMMAll/TMAll.cpp (modified) (2 diffs)

trunk/src/VBox/VMM/VMMAll/TMAll.cpp

@@ -188 +188 @@
      */
     /** @todo get TSC from caller (HMR0A.asm) */
-    uint64_t       cTicks            = SUPReadTsc() - pVCpu->tm.s.uTscStartExecuting;
+    uint64_t       cTicks = SUPReadTsc() - pVCpu->tm.s.uTscStartExecuting;
 # ifdef IN_RING3
-    uint64_t const uCpuHz            = SUPGetCpuHzFromGip(g_pSUPGlobalInfoPage);
+    uint64_t const uCpuHz = SUPGetCpuHzFromGip(g_pSUPGlobalInfoPage);
 # else
-    uint64_t const uCpuHz            = SUPGetCpuHzFromGipBySetIndex(g_pSUPGlobalInfoPage, pVCpu->iHostCpuSet);
+    uint64_t const uCpuHz = SUPGetCpuHzFromGipBySetIndex(g_pSUPGlobalInfoPage, pVCpu->iHostCpuSet);
 # endif
     AssertStmt(cTicks <= uCpuHz << 2, cTicks = uCpuHz << 2); /* max 4 sec */
@@ -209 +209 @@
     /*
      * Update the data.
+     *
+     * Note! Using ASMAtomicUoIncU32 instead of ASMAtomicIncU32 here to
+     *       save a tiny bit of time here.  Currently, the only user
+     *       is tmR3CpuLoadTimer(), so nothing terribly important.
      */
     uint64_t const cNsExecutingNew = pVCpu->tm.s.cNsExecuting + cNsExecutingDelta;
-    /** @todo try relax ordering here */
-    uint32_t uGen = ASMAtomicIncU32(&pVCpu->tm.s.uTimesGen); Assert(uGen & 1);
+    uint32_t uGen = ASMAtomicUoIncU32(&pVCpu->tm.s.uTimesGen); Assert(uGen & 1);
     pVCpu->tm.s.fExecuting   = false;
     pVCpu->tm.s.cNsExecuting = cNsExecutingNew;