[PATCH] UML - Convert the real-time clock to gettimeofday from rdtsc
From: Jeff Dike
Date: Tue Sep 14 2004 - 12:53:31 EST
There are a whole bunch of reasons to use gettimeofday rather than rdtsc,
so this patch does just that.
Signed-off-by: Jeff Dike <jdike@xxxxxxxxxxx>
Index: 2.6.9-rc2/arch/um/include/os.h
===================================================================
--- 2.6.9-rc2.orig/arch/um/include/os.h 2004-09-14 13:30:30.000000000 -0400
+++ 2.6.9-rc2/arch/um/include/os.h 2004-09-14 13:30:33.000000000 -0400
@@ -166,6 +166,7 @@
int r, int w, int x);
extern int os_unmap_memory(void *addr, int len);
extern void os_flush_stdout(void);
+extern unsigned long long os_usecs(void);
#endif
Index: 2.6.9-rc2/arch/um/kernel/time.c
===================================================================
--- 2.6.9-rc2.orig/arch/um/kernel/time.c 2004-09-14 13:30:30.000000000 -0400
+++ 2.6.9-rc2/arch/um/kernel/time.c 2004-09-14 13:30:33.000000000 -0400
@@ -10,7 +10,6 @@
#include <sys/time.h>
#include <signal.h>
#include <errno.h>
-#include <string.h>
#include "user_util.h"
#include "kern_util.h"
#include "user.h"
@@ -95,49 +94,12 @@
set_interval(ITIMER_REAL);
}
-static unsigned long long get_host_hz(void)
-{
- char mhzline[16], *end;
- unsigned long long mhz;
- int ret, mult, rest, len;
-
- ret = cpu_feature("cpu MHz", mhzline,
- sizeof(mhzline) / sizeof(mhzline[0]));
- if(!ret)
- panic ("Could not get host MHZ");
-
- mhz = strtoul(mhzline, &end, 10);
-
- /* This business is to parse a floating point number without using
- * floating types.
- */
-
- rest = 0;
- mult = 0;
- if(*end == '.'){
- end++;
- len = strlen(end);
- if(len < 6)
- mult = 6 - len;
- else if(len > 6)
- end[6] = '\0';
- rest = strtoul(end, NULL, 10);
- while(mult-- > 0)
- rest *= 10;
- }
-
- return(1000000 * mhz + rest);
-}
-
-unsigned long long host_hz = 0;
-
extern int do_posix_clock_monotonic_gettime(struct timespec *tp);
void time_init(void)
{
struct timespec now;
- host_hz = get_host_hz();
if(signal(SIGVTALRM, boot_timer_handler) == SIG_ERR)
panic("Couldn't set SIGVTALRM handler");
set_interval(ITIMER_VIRTUAL);
Index: 2.6.9-rc2/arch/um/kernel/time_kern.c
===================================================================
--- 2.6.9-rc2.orig/arch/um/kernel/time_kern.c 2004-09-14 13:30:23.000000000 -0400
+++ 2.6.9-rc2/arch/um/kernel/time_kern.c 2004-09-14 13:30:33.000000000 -0400
@@ -20,6 +20,7 @@
#include "user_util.h"
#include "time_user.h"
#include "mode.h"
+#include "os.h"
u64 jiffies_64;
@@ -42,12 +43,10 @@
int timer_irq_inited = 0;
static int first_tick;
-static unsigned long long prev_tsc;
-#ifdef CONFIG_UML_REAL_TIME_CLOCK
+static unsigned long long prev_usecs;
static long long delta; /* Deviation per interval */
-#endif
-extern unsigned long long host_hz;
+#define MILLION 1000000
void timer_irq(union uml_pt_regs *regs)
{
@@ -61,22 +60,25 @@
}
if(first_tick){
-#ifdef CONFIG_UML_REAL_TIME_CLOCK
- unsigned long long tsc;
+#if defined(CONFIG_UML_REAL_TIME_CLOCK)
/* We've had 1 tick */
- tsc = time_stamp();
+ unsigned long long usecs = os_usecs();
+
+ delta += usecs - prev_usecs;
+ prev_usecs = usecs;
- delta += tsc - prev_tsc;
- prev_tsc = tsc;
+ /* Protect against the host clock being set backwards */
+ if(delta < 0)
+ delta = 0;
- ticks += (delta * HZ) / host_hz;
- delta -= (ticks * host_hz) / HZ;
+ ticks += (delta * HZ) / MILLION;
+ delta -= (ticks * MILLION) / HZ;
#else
ticks = 1;
#endif
}
else {
- prev_tsc = time_stamp();
+ prev_usecs = os_usecs();
first_tick = 1;
}
@@ -151,7 +153,7 @@
{
int i, n;
- n = (loops_per_jiffy * HZ * usecs) / 1000000;
+ n = (loops_per_jiffy * HZ * usecs) / MILLION;
for(i=0;i<n;i++) ;
}
@@ -159,7 +161,7 @@
{
int i, n;
- n = (loops_per_jiffy * HZ * usecs) / 1000000;
+ n = (loops_per_jiffy * HZ * usecs) / MILLION;
for(i=0;i<n;i++) ;
}
Index: 2.6.9-rc2/arch/um/os-Linux/Makefile
===================================================================
--- 2.6.9-rc2.orig/arch/um/os-Linux/Makefile 2004-09-14 13:30:23.000000000 -0400
+++ 2.6.9-rc2/arch/um/os-Linux/Makefile 2004-09-14 13:30:33.000000000 -0400
@@ -3,9 +3,9 @@
# Licensed under the GPL
#
-obj-y = file.o process.o tty.o user_syms.o drivers/
+obj-y = file.o process.o time.o tty.o user_syms.o drivers/
-USER_OBJS := $(foreach file,file.o process.o tty.o,$(obj)/$(file))
+USER_OBJS := $(foreach file,file.o process.o time.o tty.o,$(obj)/$(file))
$(USER_OBJS) : %.o: %.c
$(CC) $(CFLAGS_$(notdir $@)) $(USER_CFLAGS) -c -o $@ $<
Index: 2.6.9-rc2/arch/um/os-Linux/time.c
===================================================================
--- 2.6.9-rc2.orig/arch/um/os-Linux/time.c 2003-09-15 09:40:47.000000000 -0400
+++ 2.6.9-rc2/arch/um/os-Linux/time.c 2004-09-14 13:30:33.000000000 -0400
@@ -0,0 +1,21 @@
+#include <stdlib.h>
+#include <sys/time.h>
+
+unsigned long long os_usecs(void)
+{
+ struct timeval tv;
+
+ gettimeofday(&tv, NULL);
+ return((unsigned long long) tv.tv_sec * 1000000 + tv.tv_usec);
+}
+
+/*
+ * Overrides for Emacs so that we follow Linus's tabbing style.
+ * Emacs will notice this stuff at the end of the file and automatically
+ * adjust the settings for this buffer only. This must remain at the end
+ * of the file.
+ * ---------------------------------------------------------------------------
+ * Local variables:
+ * c-file-style: "linux"
+ * End:
+ */
Index: 2.6.9-rc2/arch/um/sys-i386/Makefile
===================================================================
--- 2.6.9-rc2.orig/arch/um/sys-i386/Makefile 2004-09-14 13:30:23.000000000 -0400
+++ 2.6.9-rc2/arch/um/sys-i386/Makefile 2004-09-14 13:30:33.000000000 -0400
@@ -1,5 +1,5 @@
obj-y = bitops.o bugs.o checksum.o fault.o ksyms.o ldt.o ptrace.o \
- ptrace_user.o semaphore.o sigcontext.o syscalls.o sysrq.o time.o
+ ptrace_user.o semaphore.o sigcontext.o syscalls.o sysrq.o
obj-$(CONFIG_HIGHMEM) += highmem.o
obj-$(CONFIG_MODULES) += module.o
Index: 2.6.9-rc2/arch/um/sys-i386/time.c
===================================================================
--- 2.6.9-rc2.orig/arch/um/sys-i386/time.c 2004-09-14 13:30:23.000000000 -0400
+++ 2.6.9-rc2/arch/um/sys-i386/time.c 2003-09-15 09:40:47.000000000 -0400
@@ -1,24 +0,0 @@
-/*
- * sys-i386/time.c
- * Created 25.9.2002 Sapan Bhatia
- *
- */
-
-unsigned long long time_stamp(void)
-{
- unsigned long low, high;
-
- asm("rdtsc" : "=a" (low), "=d" (high));
- return((((unsigned long long) high) << 32) + low);
-}
-
-/*
- * Overrides for Emacs so that we follow Linus's tabbing style.
- * Emacs will notice this stuff at the end of the file and automatically
- * adjust the settings for this buffer only. This must remain at the end
- * of the file.
- * ---------------------------------------------------------------------------
- * Local variables:
- * c-file-style: "linux"
- * End:
- */
-
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