diff options
| author | Zachary Amsden <zach@vmware.com> | 2007-03-05 00:30:35 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-03-05 07:57:52 -0800 |
| commit | 6cb9a8350aee789100a365794272ed20cc8f2401 (patch) | |
| tree | c2e319b30ebcb6c9d247382303f7fcff1ab0d641 /arch/i386/kernel/tsc.c | |
| parent | 7507ba34e827ca3c6bbcd34d20a8df8ba365fca6 (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.c | 6 |
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); |