The patch titled
vmi: sched clock paravirt op fix
has been added to the -mm tree. Its filename is
vmi-sched-clock-paravirt-op-fix.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: vmi: sched clock paravirt op fix
From: Zachary Amsden <zach@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/i386/kernel/paravirt.c | 2 ++
arch/i386/kernel/tsc.c | 6 ++----
arch/i386/kernel/vmi.c | 2 +-
arch/i386/kernel/vmitime.c | 2 +-
include/asm-i386/paravirt.h | 3 +++
include/asm-i386/time.h | 1 -
include/asm-i386/timer.h | 8 +++++++-
include/asm-i386/vmi_time.h | 2 +-
8 files changed, 17 insertions(+), 9 deletions(-)
diff -puN arch/i386/kernel/paravirt.c~vmi-sched-clock-paravirt-op-fix arch/i386/kernel/paravirt.c
--- a/arch/i386/kernel/paravirt.c~vmi-sched-clock-paravirt-op-fix
+++ a/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,
diff -puN arch/i386/kernel/tsc.c~vmi-sched-clock-paravirt-op-fix arch/i386/kernel/tsc.c
--- a/arch/i386/kernel/tsc.c~vmi-sched-clock-paravirt-op-fix
+++ a/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);
diff -puN arch/i386/kernel/vmi.c~vmi-sched-clock-paravirt-op-fix arch/i386/kernel/vmi.c
--- a/arch/i386/kernel/vmi.c~vmi-sched-clock-paravirt-op-fix
+++ a/arch/i386/kernel/vmi.c
@@ -873,7 +873,7 @@ static inline int __init activate_vmi(vo
paravirt_ops.setup_boot_clock = vmi_timer_setup_boot_alarm;
paravirt_ops.setup_secondary_clock = vmi_timer_setup_secondary_alarm;
#endif
- custom_sched_clock = vmi_sched_clock;
+ paravirt_ops.get_scheduled_cycles = vmi_get_sched_cycles;
}
if (!disable_noidle)
para_fill(safe_halt, Halt);
diff -puN arch/i386/kernel/vmitime.c~vmi-sched-clock-paravirt-op-fix arch/i386/kernel/vmitime.c
--- a/arch/i386/kernel/vmitime.c~vmi-sched-clock-paravirt-op-fix
+++ a/arch/i386/kernel/vmitime.c
@@ -172,7 +172,7 @@ int vmi_set_wallclock(unsigned long now)
return -1;
}
-unsigned long long vmi_sched_clock(void)
+unsigned long long vmi_get_sched_cycles(void)
{
return read_available_cycles();
}
diff -puN include/asm-i386/paravirt.h~vmi-sched-clock-paravirt-op-fix include/asm-i386/paravirt.h
--- a/include/asm-i386/paravirt.h~vmi-sched-clock-paravirt-op-fix
+++ a/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 { \
diff -puN include/asm-i386/time.h~vmi-sched-clock-paravirt-op-fix include/asm-i386/time.h
--- a/include/asm-i386/time.h~vmi-sched-clock-paravirt-op-fix
+++ a/include/asm-i386/time.h
@@ -30,7 +30,6 @@ static inline int native_set_wallclock(u
#ifdef CONFIG_PARAVIRT
#include <asm/paravirt.h>
-extern unsigned long long native_sched_clock(void);
#else /* !CONFIG_PARAVIRT */
#define get_wallclock() native_get_wallclock()
diff -puN include/asm-i386/timer.h~vmi-sched-clock-paravirt-op-fix include/asm-i386/timer.h
--- a/include/asm-i386/timer.h~vmi-sched-clock-paravirt-op-fix
+++ a/include/asm-i386/timer.h
@@ -4,13 +4,19 @@
#include <linux/pm.h>
#define TICK_SIZE (tick_nsec / 1000)
+
void setup_pit_timer(void);
+unsigned long long native_sched_clock(void);
+
/* Modifiers for buggy PIT handling */
extern int pit_latch_buggy;
extern int timer_ack;
extern int no_timer_check;
-extern unsigned long long (*custom_sched_clock)(void);
extern int no_sync_cmos_clock;
extern int recalibrate_cpu_khz(void);
+#ifndef CONFIG_PARAVIRT
+#define get_scheduled_cycles(val) rdtscll(val)
+#endif
+
#endif
diff -puN include/asm-i386/vmi_time.h~vmi-sched-clock-paravirt-op-fix include/asm-i386/vmi_time.h
--- a/include/asm-i386/vmi_time.h~vmi-sched-clock-paravirt-op-fix
+++ a/include/asm-i386/vmi_time.h
@@ -49,7 +49,7 @@ extern struct vmi_timer_ops {
extern void __init vmi_time_init(void);
extern unsigned long vmi_get_wallclock(void);
extern int vmi_set_wallclock(unsigned long now);
-extern unsigned long long vmi_sched_clock(void);
+extern unsigned long long vmi_get_sched_cycles(void);
#ifdef CONFIG_X86_LOCAL_APIC
extern void __init vmi_timer_setup_boot_alarm(void);
_
Patches currently in -mm which might be from zach@xxxxxxxxxx are
vmi-timer-fixes-round-two.patch
vmi-sched-clock-paravirt-op-fix.patch
vmi-cpu-cycles-fix.patch
vmi-fix-highpte.patch
vmi-paravirt-drop-udelay-op.patch
vmi-pit-override.patch
vmi-fix-nohz-compile.patch
vmi-apic-ops.patch
vmi-smp-fixes.patch
make-struct-vmi_ops-static.patch
xen-paravirt_ops-rename-struct-paravirt_patch-to-paravirt_patch_site-for-clarity.patch
xen-paravirt_ops-use-patch-site-ids-computed-from-offset-in-paravirt_ops-structure.patch
xen-paravirt_ops-fix-patch-site-clobbers-to-include-return-register.patch
xen-paravirt_ops-consistently-wrap-paravirt-ops-callsites-to-make-them-patchable.patch
xen-paravirt_ops-add-common-patching-machinery.patch
xen-paravirt_ops-add-nosegneg-capability-to-the-vsyscall-page-notes.patch
-
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
