Changeset 316

Timestamp:

Jun 8, 2014, 4:48:49 PM (11 years ago)

Author:

cfuguet

Message:

boot.c:

• Initializing Local, Remote and Dirty flags of each pte2 to 1. The goal is to avoid the hardware update mechanism for these flags. This is a performance optimization that can be made because mentioned flags are not exploited by GIET_VM.

File:

• soft/giet_vm/giet_boot/boot.c (modified) (4 diffs)

soft/giet_vm/giet_boot/boot.c

@@ -412 +412 @@
 
         flags = PTE_V;
-        if (vseg[vseg_id].mode & C_MODE_MASK) flags = flags | PTE_C;
-        if (vseg[vseg_id].mode & X_MODE_MASK) flags = flags | PTE_X;
-        if (vseg[vseg_id].mode & W_MODE_MASK) flags = flags | PTE_W;
-        if (vseg[vseg_id].mode & U_MODE_MASK) flags = flags | PTE_U;
+        if (vseg[vseg_id].mode & C_MODE_MASK) flags |= PTE_C;
+        if (vseg[vseg_id].mode & X_MODE_MASK) flags |= PTE_X;
+        if (vseg[vseg_id].mode & W_MODE_MASK) flags |= PTE_W;
+        if (vseg[vseg_id].mode & U_MODE_MASK) flags |= PTE_U;
+        
+        // These three flags (Local, Remote and Dirty) are set to 1 to reduce
+        // latency of TLB miss (L/R) and write (D): Avoid hardware update
+        // mechanism for these flags. This optimization can be performed
+        // because GIET_VM does nothing with these flags.
+
+        flags |= PTE_L;
+        flags |= PTE_R;
+        flags |= PTE_D;
 
 #if BOOT_DEBUG_PT
@@ -445 +454 @@
 
         flags = PTE_V;
-        if (vseg[vseg_id].mode & C_MODE_MASK)  flags = flags | PTE_C;
-        if (vseg[vseg_id].mode & X_MODE_MASK)  flags = flags | PTE_X;
-        if (vseg[vseg_id].mode & W_MODE_MASK)  flags = flags | PTE_W;
-        if (vseg[vseg_id].mode & U_MODE_MASK)  flags = flags | PTE_U;
+        if (vseg[vseg_id].mode & C_MODE_MASK) flags |= PTE_C;
+        if (vseg[vseg_id].mode & X_MODE_MASK) flags |= PTE_X;
+        if (vseg[vseg_id].mode & W_MODE_MASK) flags |= PTE_W;
+        if (vseg[vseg_id].mode & U_MODE_MASK) flags |= PTE_U;
+
+        // Flags set for optimization (as explained above)
+
+        flags |= PTE_L;
+        flags |= PTE_R;
+        flags |= PTE_D;
 
 #if BOOT_DEBUG_PT
@@ -2049 +2064 @@
                 case PERIPH_TYPE_IOB:    // vci_io_bridge component
                 {
+#if 0
                     // initialize r_xicu_base & r_xicu_size registers
                     unsigned int base = (unsigned int)&seg_xcu_base;
@@ -2073 +2089 @@
                         // pseg_base[IOB_IOMMU_ACTIVE] = 1;        
                     }
+#endif
                     break;
                 }