[PATCH] mini-os updated

[Grzegorz Milos <gm281@cam.ac.uk>]

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Mini-os updated to use the new timer interface.

Cheers
Gregor

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# HG changeset patch
# User gmilos@localhost.localdomain
# Node ID 3068565f6a32fde5fe1c11d44fd08d876d2b633f
# Parent  082a537ff4dec66574788126b3b047ef76e59803
Mini-os updated to use the new time interface.
Signed-off-by: Grzegorz Milos <gm281@cam.ac.uk>

diff -r 082a537ff4de -r 3068565f6a32 extras/mini-os/include/time.h
--- a/extras/mini-os/include/time.h	Thu Aug 18 17:04:48 2005
+++ b/extras/mini-os/include/time.h	Fri Aug 19 16:42:51 2005
@@ -28,7 +28,7 @@
  * of real time into system time 
  */
 typedef s64 s_time_t;
-#define NOW()                   ((s_time_t)get_s_time())
+#define NOW()                   ((s_time_t)monotonic_clock())
 #define SECONDS(_s)             (((s_time_t)(_s))  * 1000000000UL )
 #define TENTHS(_ts)             (((s_time_t)(_ts)) * 100000000UL )
 #define HUNDREDTHS(_hs)         (((s_time_t)(_hs)) * 10000000UL )
@@ -36,7 +36,8 @@
 #define MICROSECS(_us)          (((s_time_t)(_us)) * 1000UL )
 #define Time_Max                ((s_time_t) 0x7fffffffffffffffLL)
 #define FOREVER                 Time_Max
-
+#define NSEC_TO_USEC(_nsec)     (_nsec / 1000UL)
+#define NSEC_TO_SEC(_nsec)      (_nsec / 1000000000ULL)
 
 /* wall clock time  */
 typedef long time_t;
@@ -44,6 +45,11 @@
 struct timeval {
 	time_t		tv_sec;		/* seconds */
 	suseconds_t	tv_usec;	/* microseconds */
+};
+
+struct timespec {
+    time_t      ts_sec;
+    long        ts_nsec;
 };
 
 
diff -r 082a537ff4de -r 3068565f6a32 extras/mini-os/kernel.c
--- a/extras/mini-os/kernel.c	Thu Aug 18 17:04:48 2005
+++ b/extras/mini-os/kernel.c	Fri Aug 19 16:42:51 2005
@@ -132,20 +132,6 @@
     i = 0;
     for ( ; ; ) 
     {      
-        if(i >= 1000)         
-        {
-            {
-                unsigned long saved;
-                __asm__ ("movl %%esp, %0"
-                         :"=r"(saved)  /* y is output operand */
-                            /* x is input operand */);
-//                        :"a"); /* %eax is clobbered register */
-                printk("ESP=0x%lx\n", saved);
-            }
-            
-            printk("1000 bloks\n");
-            i=0;            
-        }
 //        HYPERVISOR_yield();
         block(1);
         i++;
diff -r 082a537ff4de -r 3068565f6a32 extras/mini-os/time.c
--- a/extras/mini-os/time.c	Thu Aug 18 17:04:48 2005
+++ b/extras/mini-os/time.c	Fri Aug 19 16:42:51 2005
@@ -43,19 +43,20 @@
  * Time functions
  *************************************************************************/
 
-/* Cached *multiplier* to convert TSC counts to microseconds.
- * (see the equation below).
- * Equal to 2^32 * (1 / (clocks per usec) ).
- * Initialized in time_init.
- */
-static unsigned long fast_gettimeoffset_quotient;
-
-
 /* These are peridically updated in shared_info, and then copied here. */
-static u32 shadow_tsc_stamp;
-static s64 shadow_system_time;
-static u32 shadow_time_version;
-static struct timeval shadow_tv;
+struct shadow_time_info {
+	u64 tsc_timestamp;     /* TSC at last update of time vals.  */
+	u64 system_timestamp;  /* Time, in nanosecs, since boot.    */
+	u32 tsc_to_nsec_mul;
+	u32 tsc_to_usec_mul;
+	int tsc_shift;
+	u32 version;
+};
+static struct timespec shadow_ts;
+static u32 shadow_ts_version;
+
+static struct shadow_time_info shadow;
+
 
 #ifndef rmb
 #define rmb()  __asm__ __volatile__ ("lock; addl $0,0(%%esp)": : :"memory")
@@ -63,116 +64,150 @@
 
 #define HANDLE_USEC_OVERFLOW(_tv)          \
     do {                                   \
-        while ( (_tv).tv_usec >= 1000000 ) \
+        while ( (_tv)->tv_usec >= 1000000 ) \
         {                                  \
-            (_tv).tv_usec -= 1000000;      \
-            (_tv).tv_sec++;                \
+            (_tv)->tv_usec -= 1000000;      \
+            (_tv)->tv_sec++;                \
         }                                  \
     } while ( 0 )
 
+static inline int time_values_up_to_date(void)
+{
+	struct vcpu_time_info *src = &HYPERVISOR_shared_info->vcpu_time[0]; 
+
+	return (shadow.version == src->version);
+}
+
+
+/*
+ * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,
+ * yielding a 64-bit result.
+ */
+static inline u64 scale_delta(u64 delta, u32 mul_frac, int shift)
+{
+	u64 product;
+#ifdef __i386__
+	u32 tmp1, tmp2;
+#endif
+
+	if ( shift < 0 )
+		delta >>= -shift;
+	else
+		delta <<= shift;
+
+#ifdef __i386__
+	__asm__ (
+		"mul  %5       ; "
+		"mov  %4,%%eax ; "
+		"mov  %%edx,%4 ; "
+		"mul  %5       ; "
+		"add  %4,%%eax ; "
+		"xor  %5,%5    ; "
+		"adc  %5,%%edx ; "
+		: "=A" (product), "=r" (tmp1), "=r" (tmp2)
+		: "a" ((u32)delta), "1" ((u32)(delta >> 32)), "2" (mul_frac) );
+#else
+	__asm__ (
+		"mul %%rdx ; shrd $32,%%rdx,%%rax"
+		: "=a" (product) : "0" (delta), "d" ((u64)mul_frac) );
+#endif
+
+	return product;
+}
+
+
+static unsigned long get_nsec_offset(void)
+{
+	u64 now, delta;
+	rdtscll(now);
+	delta = now - shadow.tsc_timestamp;
+	return scale_delta(delta, shadow.tsc_to_nsec_mul, shadow.tsc_shift);
+}
+
+
 static void get_time_values_from_xen(void)
 {
-    do {
-        shadow_time_version = HYPERVISOR_shared_info->time_version2;
-        rmb();
-        shadow_tv.tv_sec    = HYPERVISOR_shared_info->wc_sec;
-        shadow_tv.tv_usec   = HYPERVISOR_shared_info->wc_usec;
-        shadow_tsc_stamp    = (u32)HYPERVISOR_shared_info->tsc_timestamp;
-        shadow_system_time  = HYPERVISOR_shared_info->system_time;
-        rmb();
-    }
-    while ( shadow_time_version != HYPERVISOR_shared_info->time_version1 );
-}
-
-
-#define TIME_VALUES_UP_TO_DATE \
-    (shadow_time_version == HYPERVISOR_shared_info->time_version2)
-
-static u32  get_time_delta_usecs(void)
-{
-	register unsigned long eax, edx;
-
-	/* Read the Time Stamp Counter */
-
-	rdtsc(eax,edx);
-
-	/* .. relative to previous jiffy (32 bits is enough) */
-	eax -= shadow_tsc_stamp;
-
-	/*
-	 * Time offset = (tsc_low delta) * fast_gettimeoffset_quotient
-	 *             = (tsc_low delta) * (usecs_per_clock)
-	 *             = (tsc_low delta) * (usecs_per_jiffy / clocks_per_jiffy)
-	 *
-	 * Using a mull instead of a divl saves up to 31 clock cycles
-	 * in the critical path.
-	 */
-
-	__asm__("mull %2"
-		:"=a" (eax), "=d" (edx)
-		:"rm" (fast_gettimeoffset_quotient),
-		 "0" (eax));
-
-	/* our adjusted time offset in microseconds */
-	return edx;
-}
-
-s64 get_s_time (void)
-{
-    u64 u_delta;
-    s64 ret;
-
- again:
-
-    u_delta = get_time_delta_usecs();
-    ret = shadow_system_time + (1000 * u_delta);
-
-    if ( unlikely(!TIME_VALUES_UP_TO_DATE) )
-    {
-        /*
-         * We may have blocked for a long time, rendering our calculations
-         * invalid (e.g. the time delta may have overflowed). Detect that
-         * and recalculate with fresh values.
-         */
-        get_time_values_from_xen();
-        goto again;
-    }
-
-    return ret;
-}
+	struct vcpu_time_info    *src = &HYPERVISOR_shared_info->vcpu_time[0];
+
+ 	do {
+		shadow.version = src->version;
+		rmb();
+		shadow.tsc_timestamp     = src->tsc_timestamp;
+		shadow.system_timestamp  = src->system_time;
+		shadow.tsc_to_nsec_mul   = src->tsc_to_system_mul;
+		shadow.tsc_shift         = src->tsc_shift;
+		rmb();
+	}
+	while ((src->version & 1) | (shadow.version ^ src->version));
+
+	shadow.tsc_to_usec_mul = shadow.tsc_to_nsec_mul / 1000;
+}
+
+
+
+
+/* monotonic_clock(): returns # of nanoseconds passed since time_init()
+ *		Note: This function is required to return accurate
+ *		time even in the absence of multiple timer ticks.
+ */
+u64 monotonic_clock(void)
+{
+	u64 time;
+	u32 local_time_version;
+
+	do {
+		local_time_version = shadow.version;
+		rmb();
+		time = shadow.system_timestamp + get_nsec_offset();
+        if (!time_values_up_to_date())
+			get_time_values_from_xen();
+		rmb();
+	} while (local_time_version != shadow.version);
+
+	return time;
+}
+
+static void update_wallclock(void)
+{
+	shared_info_t *s = HYPERVISOR_shared_info;
+
+	do {
+		shadow_ts_version = s->wc_version;
+		rmb();
+		shadow_ts.ts_sec  = s->wc_sec;
+		shadow_ts.ts_nsec = s->wc_nsec;
+		rmb();
+	}
+	while ((s->wc_version & 1) | (shadow_ts_version ^ s->wc_version));
+}
+
 
 void gettimeofday(struct timeval *tv)
 {
-    struct timeval _tv;
-
-    do {
-        get_time_values_from_xen();
-        _tv.tv_usec = get_time_delta_usecs();
-        _tv.tv_sec   = shadow_tv.tv_sec;
-        _tv.tv_usec += shadow_tv.tv_usec;
-    }
-    while ( unlikely(!TIME_VALUES_UP_TO_DATE) );
-
-    HANDLE_USEC_OVERFLOW(_tv);
-    *tv = _tv;
-}
+    u64 nsec = monotonic_clock();
+    nsec += shadow_ts.ts_nsec;
+    
+    
+    tv->tv_sec = shadow_ts.ts_sec;
+    tv->tv_sec += NSEC_TO_SEC(nsec);
+    tv->tv_usec = NSEC_TO_USEC(nsec % 1000000000UL);
+}
+
 
 static void print_current_time(void)
 {
-    struct timeval tv;
-
-    get_time_values_from_xen();
+    struct timeval tv;    
 
     gettimeofday(&tv);
     printk("T(s=%ld us=%ld)\n", tv.tv_sec, tv.tv_usec);
 }
 
+
 void block(u32 millisecs)
 {
     struct timeval tv;
     gettimeofday(&tv);
-    //printk("tv.tv_sec=%ld, tv.tv_usec=%ld, shadow_system_time=%lld\n", tv.tv_sec, tv.tv_usec, shadow_system_time );
-    HYPERVISOR_set_timer_op(get_s_time() + 1000000LL * (s64) millisecs);
+    HYPERVISOR_set_timer_op(monotonic_clock() + 1000000LL * (s64) millisecs);
     HYPERVISOR_block();
 }
 
@@ -185,7 +220,7 @@
     static int i;
 
     get_time_values_from_xen();
-
+    update_wallclock();
     i++;
     if (i >= 1000) {
         print_current_time();
@@ -197,24 +232,5 @@
 
 void init_time(void)
 {
-    u64         __cpu_khz;
-    unsigned long cpu_khz;
-
-    __cpu_khz = HYPERVISOR_shared_info->cpu_freq;
-
-    cpu_khz = (u32) (__cpu_khz/1000);
-
-    printk("Xen reported: %lu.%03lu MHz processor.\n", 
-           cpu_khz / 1000, cpu_khz % 1000);
-	/* (10^6 * 2^32) / cpu_hz = (10^3 * 2^32) / cpu_khz =
-	   (2^32 * 1 / (clocks/us)) */
-	{	
-		unsigned long eax=0, edx=1000;
-		__asm__("divl %2"
-		    :"=a" (fast_gettimeoffset_quotient), "=d" (edx)
-		    :"r" (cpu_khz),
-		    "0" (eax), "1" (edx));
-	}
-
     bind_virq(VIRQ_TIMER, &timer_handler);
 }

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