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authorZachary Amsden <zach@vmware.com>2007-03-05 00:30:35 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-03-05 07:57:52 -0800
commit6cb9a8350aee789100a365794272ed20cc8f2401 (patch)
treec2e319b30ebcb6c9d247382303f7fcff1ab0d641 /arch/i386/kernel/tsc.c
parent7507ba34e827ca3c6bbcd34d20a8df8ba365fca6 (diff)
[PATCH] vmi: sched clock paravirt op fix
The custom_sched_clock hook is broken. The result from sched_clock needs to be in nanoseconds, not in CPU cycles. The TSC is insufficient for this purpose, because TSC is poorly defined in a virtual environment, and mostly represents real world time instead of scheduled process time (which can be interrupted without notice when a virtual machine is descheduled). To make the scheduler consistent, we must expose a different nature of time, that is scheduled time. So deprecate this custom_sched_clock hack and turn it into a paravirt-op, as it should have been all along. This allows the tsc.c code which converts cycles to nanoseconds to be shared by all paravirt-ops backends. It is unfortunate to add a new paravirt-op, but this is a very distinct abstraction which is clearly different for all virtual machine implementations, and it gets rid of an ugly indirect function which I ashamedly admit I hacked in to try to get this to work earlier, and then even got in the wrong units. Signed-off-by: Zachary Amsden <zach@vmware.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/i386/kernel/tsc.c')
-rw-r--r--arch/i386/kernel/tsc.c6
1 files changed, 2 insertions, 4 deletions
diff --git a/arch/i386/kernel/tsc.c b/arch/i386/kernel/tsc.c
index 3082a418635..c9c9d54c91f 100644
--- a/arch/i386/kernel/tsc.c
+++ b/arch/i386/kernel/tsc.c
@@ -14,6 +14,7 @@
#include <asm/delay.h>
#include <asm/tsc.h>
#include <asm/io.h>
+#include <asm/timer.h>
#include "mach_timer.h"
@@ -102,9 +103,6 @@ unsigned long long sched_clock(void)
{
unsigned long long this_offset;
- if (unlikely(custom_sched_clock))
- return (*custom_sched_clock)();
-
/*
* Fall back to jiffies if there's no TSC available:
*/
@@ -113,7 +111,7 @@ unsigned long long sched_clock(void)
return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);
/* read the Time Stamp Counter: */
- rdtscll(this_offset);
+ get_scheduled_cycles(this_offset);
/* return the value in ns */
return cycles_2_ns(this_offset);