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| 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/paravirt.c | |
| parent | [PATCH] vmi: timer fixes round two (diff) | |
| download | linux-dev-6cb9a8350aee789100a365794272ed20cc8f2401.tar.xz linux-dev-6cb9a8350aee789100a365794272ed20cc8f2401.zip | |
[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/paravirt.c')
| -rw-r--r-- | arch/i386/kernel/paravirt.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/i386/kernel/paravirt.c b/arch/i386/kernel/paravirt.c index c156ecfa3872..31bbe70d1e02 100644 --- a/arch/i386/kernel/paravirt.c +++ b/arch/i386/kernel/paravirt.c @@ -32,6 +32,7 @@ #include <asm/fixmap.h> #include <asm/apic.h> #include <asm/tlbflush.h> +#include <asm/timer.h> /* nop stub */ static void native_nop(void) @@ -520,6 +521,7 @@ struct paravirt_ops paravirt_ops = { .write_msr = native_write_msr, .read_tsc = native_read_tsc, .read_pmc = native_read_pmc, + .get_scheduled_cycles = native_read_tsc, .load_tr_desc = native_load_tr_desc, .set_ldt = native_set_ldt, .load_gdt = native_load_gdt, |