[Xen-devel] [PATCH 5 of 8] xenalyze: Rework math to remove two 64-bit divisions

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

abs_cycles_to_time is called on every record for dump mode; it has
four 64-bit divisions (well, 3 divisions and 1 mod), which map to
library functions on a 32-bit platform.  A simple rework of the math
can eliminate two of those.

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

diff -r 0663e3e8f69d -r 4b3639bd3255 xenalyze.c
--- a/xenalyze.c        Thu Jan 26 17:16:59 2012 +0000
+++ b/xenalyze.c        Thu Jan 26 17:17:19 2012 +0000
@@ -1976,16 +1976,19 @@ void cpumask_union(cpu_mask_t *d, const 
 /* -- Time code -- */
 
 void cycles_to_time(unsigned long long c, struct time_struct *t) {
-    t->time = ((c) * 1000) / (opt.cpu_hz / 1000000 );    
-    t->s = t->time / 1000000000;                        
-    t->ns = t->time % 1000000000;                       
+    t->time = ((c - P.f.first_tsc) * 1000 * 1000000) / opt.cpu_hz;
+    t->s = t->time / 1000000000;
+    t->ns = t->time - (t->s * 1000000000);
 }
 
 void abs_cycles_to_time(unsigned long long ac, struct time_struct *t) {
     if(ac > P.f.first_tsc) {
-        t->time = ((ac - P.f.first_tsc) * 1000) / (opt.cpu_hz / 1000000 );    
-        t->s = t->time / 1000000000;                        
-        t->ns = t->time % 1000000000;
+        /* t->time = ((ac - P.f.first_tsc) * 1000) / (opt.cpu_hz / 1000000 );  
   */
+        /* t->s = t->time / 1000000000;                         */
+        /* t->ns = t->time % 1000000000; */
+        t->time = ((ac - P.f.first_tsc) * 1000 * 1000000) / opt.cpu_hz;
+        t->s = t->time / 1000000000;
+        t->ns = t->time - (t->s * 1000000000);
     } else {
         t->time = t->s = t->ns = 0;
     }

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