Changeset 818 for soft

Timestamp:

Apr 28, 2016, 1:12:23 PM (8 years ago)

Author:

cfuguet

Message:

Optimization: When doing a context switch between threads of the
same vspace and cluster, do not rewrite the PTPR register.

Location:

soft/giet_vm/giet_kernel

Files:

• ctx_handler.c (modified) (2 diffs)
• switch.s (modified) (1 diff)

soft/giet_vm/giet_kernel/ctx_handler.c

@@ -180 +180 @@
         // makes context switch
         _thread_switch( curr_ctx_vaddr , next_ctx_vaddr );
+
+        // only modify the PTPR when necessary, in order to avoid unnecessary
+        // TLBs flush.
+        if (curr_ctx_vaddr->slot[CTX_PTPR_ID] !=
+            next_ctx_vaddr->slot[CTX_PTPR_ID])
+        {
+            _set_mmu_ptpr(next_ctx_vaddr->slot[CTX_PTPR_ID]);
+        }
     }
 } //end _ctx_switch()
@@ -195 +203 @@
     while(1)
     {
-        // initialize counter
-        unsigned int count = GIET_IDLE_THREAD_PERIOD;
-
-        // decounting loop
-        asm volatile(
-                "move   $3,   %0              \n"
-                "_idle_thread_loop:             \n"
-                "addi   $3,   $3,   -1        \n"
-                "bnez   $3,   _idle_thread_loop \n"
-                "nop                          \n"
-                :
-                : "r"(count)
-                : "$3" ); 
+        _sleep( GIET_IDLE_THREAD_PERIOD );
 
         // warning message
-        _printf("\n[GIET WARNING] Processor[%d,%d,%d] still idle at cycle %d",
+        _printf("\n[GIET WARNING] Processor[%d,%d,%d] still idle at cycle %u",
                 x , y , p , _get_proctime() );
     }

soft/giet_vm/giet_kernel/switch.s

@@ -116 +116 @@
     lw      $26,    35*4($27)
     mtc0    $26,    $8          /* restore BVAR */
-    lw      $26,    39*4($27)
-    mtc2    $26,    $0          /* restore PTPR */
 
     /* returns to caller */