Re: [Qemu-devel] Re: [PATCH 05/26] Unexport ticks_per_sec variable. Create get_ticks_per_sec() function

[Anthony Liguori <anthony@codemonkey.ws>]

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malc wrote:
> And generalizations are always true. Anyhow, i'm explicitly against the
> patch, so first obtain the express acknowledgment from the leaders,
> otherwise i'll revert it should it go in.
>   

I'm adding the following patch to Juan's series.  The result is that 
get_ticks_per_sec() should be optimized to a literal value.  The result 
being that uses of it are faster than they were before (not it should 
matter).

I think the result of this patch is that the refactoring is an 
undeniable improvement.

Regards,

Anthony Liguori



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commit 1c7aff17af0ca9e1803b952ce455f096c5da8847
Author: Anthony Liguori <aliguori@us.ibm.com>
Date:   Fri Sep 11 10:28:26 2009 -0500

    Make get_ticks_per_sec() a static inline
    
    ticks_per_sec is a constant.  There's no need to store it as a variable as it
    never changes since our time is based on units.
    
    Convert get_ticks_per_sec() to a static inline and move the constant into
    qemu-timer.h.  Remove all references to QEMU_TIMER_BASE so that we consistently
    use this interface.
    
    Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

diff --git a/qemu-timer.h b/qemu-timer.h
index 00b166d..e44c334 100644
--- a/qemu-timer.h
+++ b/qemu-timer.h
@@ -26,7 +26,10 @@ void qemu_mod_timer(QEMUTimer *ts, int64_t expire_time);
 int qemu_timer_pending(QEMUTimer *ts);
 int qemu_timer_expired(QEMUTimer *timer_head, int64_t current_time);
 
-int64_t get_ticks_per_sec(void);
+static inline int64_t get_ticks_per_sec(void)
+{
+    return 1000000000LL;
+}
 
 void qemu_get_timer(QEMUFile *f, QEMUTimer *ts);
 void qemu_put_timer(QEMUFile *f, QEMUTimer *ts);
diff --git a/vl.c b/vl.c
index 6052b1c..c3c874d 100644
--- a/vl.c
+++ b/vl.c
@@ -528,8 +528,6 @@ uint64_t muldiv64(uint64_t a, uint32_t b, uint32_t c)
 /***********************************************************/
 /* real time host monotonic timer */
 
-#define QEMU_TIMER_BASE 1000000000LL
-
 #ifdef WIN32
 
 static int64_t clock_freq;
@@ -550,7 +548,7 @@ static int64_t get_clock(void)
 {
     LARGE_INTEGER ti;
     QueryPerformanceCounter(&ti);
-    return muldiv64(ti.QuadPart, QEMU_TIMER_BASE, clock_freq);
+    return muldiv64(ti.QuadPart, get_ticks_per_sec(), clock_freq);
 }
 
 #else
@@ -758,7 +756,7 @@ static void rtc_stop_timer(struct qemu_alarm_timer *t);
    fairly approximate, so ignore small variation.
    When the guest is idle real and virtual time will be aligned in
    the IO wait loop.  */
-#define ICOUNT_WOBBLE (QEMU_TIMER_BASE / 10)
+#define ICOUNT_WOBBLE (get_ticks_per_sec() / 10)
 
 static void icount_adjust(void)
 {
@@ -800,7 +798,7 @@ static void icount_adjust_rt(void * opaque)
 static void icount_adjust_vm(void * opaque)
 {
     qemu_mod_timer(icount_vm_timer,
-                   qemu_get_clock(vm_clock) + QEMU_TIMER_BASE / 10);
+                   qemu_get_clock(vm_clock) + get_ticks_per_sec() / 10);
     icount_adjust();
 }
 
@@ -816,7 +814,7 @@ static void init_icount_adjust(void)
                    qemu_get_clock(rt_clock) + 1000);
     icount_vm_timer = qemu_new_timer(vm_clock, icount_adjust_vm, NULL);
     qemu_mod_timer(icount_vm_timer,
-                   qemu_get_clock(vm_clock) + QEMU_TIMER_BASE / 10);
+                   qemu_get_clock(vm_clock) + get_ticks_per_sec() / 10);
 }
 
 static struct qemu_alarm_timer alarm_timers[] = {
@@ -1036,15 +1034,10 @@ int64_t qemu_get_clock(QEMUClock *clock)
     }
 }
 
-int64_t get_ticks_per_sec(void)
-{
-    return timers_state.ticks_per_sec;
-}
-
 static void init_timers(void)
 {
     init_get_clock();
-    timers_state.ticks_per_sec = QEMU_TIMER_BASE;
+    timers_state.ticks_per_sec = get_ticks_per_sec();
     rt_clock = qemu_new_clock(QEMU_TIMER_REALTIME);
     vm_clock = qemu_new_clock(QEMU_TIMER_VIRTUAL);
 }