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 /include/asm-i386/paravirt.h | |
| 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 'include/asm-i386/paravirt.h')
| -rw-r--r-- | include/asm-i386/paravirt.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/include/asm-i386/paravirt.h b/include/asm-i386/paravirt.h index 6317e0a4d73..a13230254f4 100644 --- a/include/asm-i386/paravirt.h +++ b/include/asm-i386/paravirt.h @@ -94,6 +94,7 @@ struct paravirt_ops u64 (*read_tsc)(void); u64 (*read_pmc)(void); + u64 (*get_scheduled_cycles)(void); void (*load_tr_desc)(void); void (*load_gdt)(const struct Xgt_desc_struct *); @@ -273,6 +274,8 @@ static inline void halt(void) #define rdtscll(val) (val = paravirt_ops.read_tsc()) +#define get_scheduled_cycles(val) (val = paravirt_ops.get_scheduled_cycles()) + #define write_tsc(val1,val2) wrmsr(0x10, val1, val2) #define rdpmc(counter,low,high) do { \ |