[Xen-devel] [PATCH 12 of 12] xenalyze: Make max_active_pcpu calculation smarter

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

oprofile reports that during summary runs, over 30% of the
time processing is spent in choose_next_record.  As a first
step towards eliminating the loop found in that function,
take out the calculation of P.max_active_pcpu, and make it
smarter.

Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>

diff -r b7d88a8858b7 -r 223e8ad4c755 xenalyze.c
--- a/xenalyze.c        Mon Nov 28 16:16:23 2011 +0000
+++ b/xenalyze.c        Mon Nov 28 16:16:23 2011 +0000
@@ -8675,6 +8675,21 @@ void deactivate_pcpu(struct pcpu_info *p
         lose_vcpu(p->current, p->last_tsc);
     }
     p->active = 0;
+    if ( p->pid == P.max_active_pcpu )
+    {
+        int i, max_active_pcpu = -1;
+        for(i=0; i<=P.max_active_pcpu; i++)
+        {
+            if(!P.pcpu[i].active)
+                continue;
+
+            max_active_pcpu = i;
+        }
+        P.max_active_pcpu = max_active_pcpu;
+        fprintf(warn, "%s: Setting max_active_pcpu to %d\n",
+                __func__, max_active_pcpu);
+    }
+        
 }
 
 /* Helper function to process tsc-related record info */
@@ -9304,17 +9319,20 @@ char * pcpu_string(int pcpu)
 
 struct pcpu_info * choose_next_record(void)
 {
-    int i, max_active_pcpu = -1;
+    int i;
     struct pcpu_info * p, *min_p=NULL;
     loff_t min_offset = 0;
 
+    /* Need to:
+     * - find the pcpu with the lowest order_tsc
+     * - Find the lowest file offset
+     */
     for(i=0; i<=P.max_active_pcpu; i++)
     {
         p = P.pcpu+i;
         if(!p->active)
             continue;
 
-        max_active_pcpu = i;
         if(!min_p || p->order_tsc < min_p->order_tsc)
             min_p = p;
 
@@ -9322,13 +9340,11 @@ struct pcpu_info * choose_next_record(vo
             min_offset = p->file_offset;
     }
 
-    P.max_active_pcpu = max_active_pcpu;
-
     if(opt.progress && min_offset >= G.progress.update_offset)
         progress_update(min_offset);
 
     /* If there are active pcpus, make sure we chose one */
-    assert(min_p || (max_active_pcpu==-1));
+    assert(min_p || (P.max_active_pcpu==-1));
 
     return min_p;
 }

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