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authorJeremy Fitzhardinge <jeremy@xensource.com>2007-07-17 18:37:04 -0700
committerJeremy Fitzhardinge <jeremy@goop.org>2007-07-18 08:47:42 -0700
commit688340ea34c61ad12473ccd837325b59aada9a93 (patch)
tree2862f4dca8d47fc4e6ecfaba2243d813344e3cd2 /arch/i386/kernel
parentd572929cdd12a60732c3522f7cf011bfa29165cf (diff)
Add a sched_clock paravirt_op
The tsc-based get_scheduled_cycles interface is not a good match for Xen's runstate accounting, which reports everything in nanoseconds. This patch replaces this interface with a sched_clock interface, which matches both Xen and VMI's requirements. In order to do this, we: 1. replace get_scheduled_cycles with sched_clock 2. hoist cycles_2_ns into a common header 3. update vmi accordingly One thing to note: because sched_clock is implemented as a weak function in kernel/sched.c, we must define a real function in order to override this weak binding. This means the usual paravirt_ops technique of using an inline function won't work in this case. Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com> Cc: Zachary Amsden <zach@vmware.com> Cc: Dan Hecht <dhecht@vmware.com> Cc: john stultz <johnstul@us.ibm.com>
Diffstat (limited to 'arch/i386/kernel')
-rw-r--r--arch/i386/kernel/paravirt.c2
-rw-r--r--arch/i386/kernel/tsc.c23
-rw-r--r--arch/i386/kernel/vmi.c2
-rw-r--r--arch/i386/kernel/vmiclock.c6
4 files changed, 20 insertions, 13 deletions
diff --git a/arch/i386/kernel/paravirt.c b/arch/i386/kernel/paravirt.c
index 60e08b9b50a..53f07a8275e 100644
--- a/arch/i386/kernel/paravirt.c
+++ b/arch/i386/kernel/paravirt.c
@@ -302,7 +302,7 @@ struct paravirt_ops paravirt_ops = {
.write_msr = native_write_msr_safe,
.read_tsc = native_read_tsc,
.read_pmc = native_read_pmc,
- .get_scheduled_cycles = native_read_tsc,
+ .sched_clock = native_sched_clock,
.get_cpu_khz = native_calculate_cpu_khz,
.load_tr_desc = native_load_tr_desc,
.set_ldt = native_set_ldt,
diff --git a/arch/i386/kernel/tsc.c b/arch/i386/kernel/tsc.c
index ea63a30ca3e..252f9010f28 100644
--- a/arch/i386/kernel/tsc.c
+++ b/arch/i386/kernel/tsc.c
@@ -84,7 +84,7 @@ static inline int check_tsc_unstable(void)
*
* -johnstul@us.ibm.com "math is hard, lets go shopping!"
*/
-static unsigned long cyc2ns_scale __read_mostly;
+unsigned long cyc2ns_scale __read_mostly;
#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
@@ -93,15 +93,10 @@ static inline void set_cyc2ns_scale(unsigned long cpu_khz)
cyc2ns_scale = (1000000 << CYC2NS_SCALE_FACTOR)/cpu_khz;
}
-static inline unsigned long long cycles_2_ns(unsigned long long cyc)
-{
- return (cyc * cyc2ns_scale) >> CYC2NS_SCALE_FACTOR;
-}
-
/*
* Scheduler clock - returns current time in nanosec units.
*/
-unsigned long long sched_clock(void)
+unsigned long long native_sched_clock(void)
{
unsigned long long this_offset;
@@ -118,12 +113,24 @@ unsigned long long sched_clock(void)
return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);
/* read the Time Stamp Counter: */
- get_scheduled_cycles(this_offset);
+ rdtscll(this_offset);
/* return the value in ns */
return cycles_2_ns(this_offset);
}
+/* We need to define a real function for sched_clock, to override the
+ weak default version */
+#ifdef CONFIG_PARAVIRT
+unsigned long long sched_clock(void)
+{
+ return paravirt_sched_clock();
+}
+#else
+unsigned long long sched_clock(void)
+ __attribute__((alias("native_sched_clock")));
+#endif
+
unsigned long native_calculate_cpu_khz(void)
{
unsigned long long start, end;
diff --git a/arch/i386/kernel/vmi.c b/arch/i386/kernel/vmi.c
index 234bd6ff518..72042bb7ec9 100644
--- a/arch/i386/kernel/vmi.c
+++ b/arch/i386/kernel/vmi.c
@@ -891,7 +891,7 @@ static inline int __init activate_vmi(void)
paravirt_ops.setup_boot_clock = vmi_time_bsp_init;
paravirt_ops.setup_secondary_clock = vmi_time_ap_init;
#endif
- paravirt_ops.get_scheduled_cycles = vmi_get_sched_cycles;
+ paravirt_ops.sched_clock = vmi_sched_clock;
paravirt_ops.get_cpu_khz = vmi_cpu_khz;
/* We have true wallclock functions; disable CMOS clock sync */
diff --git a/arch/i386/kernel/vmiclock.c b/arch/i386/kernel/vmiclock.c
index 26a37f8a876..f9b845f4e69 100644
--- a/arch/i386/kernel/vmiclock.c
+++ b/arch/i386/kernel/vmiclock.c
@@ -64,10 +64,10 @@ int vmi_set_wallclock(unsigned long now)
return 0;
}
-/* paravirt_ops.get_scheduled_cycles = vmi_get_sched_cycles */
-unsigned long long vmi_get_sched_cycles(void)
+/* paravirt_ops.sched_clock = vmi_sched_clock */
+unsigned long long vmi_sched_clock(void)
{
- return vmi_timer_ops.get_cycle_counter(VMI_CYCLES_AVAILABLE);
+ return cycles_2_ns(vmi_timer_ops.get_cycle_counter(VMI_CYCLES_AVAILABLE));
}
/* paravirt_ops.get_cpu_khz = vmi_cpu_khz */