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Message-Id: <1463636592-13817-1-git-send-email-jgross@suse.com>
Date: Thu, 19 May 2016 07:43:12 +0200
From: Juergen Gross <jgross@...e.com>
To: xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Cc: sstabellini@...nel.org, boris.ostrovsky@...cle.com,
david.vrabel@...rix.com, Juergen Gross <jgross@...e.com>
Subject: [PATCH v2] xen: add steal_clock support on x86
The pv_time_ops structure contains a function pointer for the
"steal_clock" functionality used only by KVM and Xen on ARM. Xen on x86
uses its own mechanism to account for the "stolen" time a thread wasn't
able to run due to hypervisor scheduling.
Add support in Xen arch independent time handling for this feature by
moving it out of the arm arch into drivers/xen and remove the x86 Xen
hack.
Signed-off-by: Juergen Gross <jgross@...e.com>
---
V2: remove the x86 do_stolen_accounting() hack
---
arch/arm/xen/enlighten.c | 17 ++---------------
arch/x86/xen/time.c | 44 ++------------------------------------------
drivers/xen/time.c | 19 +++++++++++++++++++
include/linux/kernel_stat.h | 1 -
include/xen/xen-ops.h | 1 +
kernel/sched/cputime.c | 10 ----------
6 files changed, 24 insertions(+), 68 deletions(-)
diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index 75cd734..9163b94 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -84,19 +84,6 @@ int xen_unmap_domain_gfn_range(struct vm_area_struct *vma,
}
EXPORT_SYMBOL_GPL(xen_unmap_domain_gfn_range);
-static unsigned long long xen_stolen_accounting(int cpu)
-{
- struct vcpu_runstate_info state;
-
- BUG_ON(cpu != smp_processor_id());
-
- xen_get_runstate_snapshot(&state);
-
- WARN_ON(state.state != RUNSTATE_running);
-
- return state.time[RUNSTATE_runnable] + state.time[RUNSTATE_offline];
-}
-
static void xen_read_wallclock(struct timespec64 *ts)
{
u32 version;
@@ -355,8 +342,8 @@ static int __init xen_guest_init(void)
register_cpu_notifier(&xen_cpu_notifier);
- pv_time_ops.steal_clock = xen_stolen_accounting;
- static_key_slow_inc(¶virt_steal_enabled);
+ xen_time_setup_guest();
+
if (xen_initial_domain())
pvclock_gtod_register_notifier(&xen_pvclock_gtod_notifier);
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index a0a4e55..6be31df 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -11,8 +11,6 @@
#include <linux/interrupt.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>
-#include <linux/kernel_stat.h>
-#include <linux/math64.h>
#include <linux/gfp.h>
#include <linux/slab.h>
#include <linux/pvclock_gtod.h>
@@ -31,44 +29,6 @@
/* Xen may fire a timer up to this many ns early */
#define TIMER_SLOP 100000
-#define NS_PER_TICK (1000000000LL / HZ)
-
-/* snapshots of runstate info */
-static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate_snapshot);
-
-/* unused ns of stolen time */
-static DEFINE_PER_CPU(u64, xen_residual_stolen);
-
-static void do_stolen_accounting(void)
-{
- struct vcpu_runstate_info state;
- struct vcpu_runstate_info *snap;
- s64 runnable, offline, stolen;
- cputime_t ticks;
-
- xen_get_runstate_snapshot(&state);
-
- WARN_ON(state.state != RUNSTATE_running);
-
- snap = this_cpu_ptr(&xen_runstate_snapshot);
-
- /* work out how much time the VCPU has not been runn*ing* */
- runnable = state.time[RUNSTATE_runnable] - snap->time[RUNSTATE_runnable];
- offline = state.time[RUNSTATE_offline] - snap->time[RUNSTATE_offline];
-
- *snap = state;
-
- /* Add the appropriate number of ticks of stolen time,
- including any left-overs from last time. */
- stolen = runnable + offline + __this_cpu_read(xen_residual_stolen);
-
- if (stolen < 0)
- stolen = 0;
-
- ticks = iter_div_u64_rem(stolen, NS_PER_TICK, &stolen);
- __this_cpu_write(xen_residual_stolen, stolen);
- account_steal_ticks(ticks);
-}
/* Get the TSC speed from Xen */
static unsigned long xen_tsc_khz(void)
@@ -335,8 +295,6 @@ static irqreturn_t xen_timer_interrupt(int irq, void *dev_id)
ret = IRQ_HANDLED;
}
- do_stolen_accounting();
-
return ret;
}
@@ -431,6 +389,8 @@ static void __init xen_time_init(void)
xen_setup_timer(cpu);
xen_setup_cpu_clockevents();
+ xen_time_setup_guest();
+
if (xen_initial_domain())
pvclock_gtod_register_notifier(&xen_pvclock_gtod_notifier);
}
diff --git a/drivers/xen/time.c b/drivers/xen/time.c
index 7107842..6648a78 100644
--- a/drivers/xen/time.c
+++ b/drivers/xen/time.c
@@ -75,6 +75,15 @@ bool xen_vcpu_stolen(int vcpu)
return per_cpu(xen_runstate, vcpu).state == RUNSTATE_runnable;
}
+static u64 xen_steal_clock(int cpu)
+{
+ struct vcpu_runstate_info state;
+
+ BUG_ON(cpu != smp_processor_id());
+ xen_get_runstate_snapshot(&state);
+ return state.time[RUNSTATE_runnable] + state.time[RUNSTATE_offline];
+}
+
void xen_setup_runstate_info(int cpu)
{
struct vcpu_register_runstate_memory_area area;
@@ -86,3 +95,13 @@ void xen_setup_runstate_info(int cpu)
BUG();
}
+void __init xen_time_setup_guest(void)
+{
+ pv_time_ops.steal_clock = xen_steal_clock;
+
+ static_key_slow_inc(¶virt_steal_enabled);
+ /*
+ * We can't set paravirt_steal_rq_enabled as this would require the
+ * capability to read another cpu's runstate info.
+ */
+}
diff --git a/include/linux/kernel_stat.h b/include/linux/kernel_stat.h
index 25a822f..44fda64 100644
--- a/include/linux/kernel_stat.h
+++ b/include/linux/kernel_stat.h
@@ -92,7 +92,6 @@ static inline void account_process_tick(struct task_struct *tsk, int user)
extern void account_process_tick(struct task_struct *, int user);
#endif
-extern void account_steal_ticks(unsigned long ticks);
extern void account_idle_ticks(unsigned long ticks);
#endif /* _LINUX_KERNEL_STAT_H */
diff --git a/include/xen/xen-ops.h b/include/xen/xen-ops.h
index 86abe07..5ce51c2 100644
--- a/include/xen/xen-ops.h
+++ b/include/xen/xen-ops.h
@@ -21,6 +21,7 @@ void xen_resume_notifier_unregister(struct notifier_block *nb);
bool xen_vcpu_stolen(int vcpu);
void xen_setup_runstate_info(int cpu);
+void __init xen_time_setup_guest(void);
void xen_get_runstate_snapshot(struct vcpu_runstate_info *res);
int xen_setup_shutdown_event(void);
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 75f98c5..8c4c6dc 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -490,16 +490,6 @@ void account_process_tick(struct task_struct *p, int user_tick)
}
/*
- * Account multiple ticks of steal time.
- * @p: the process from which the cpu time has been stolen
- * @ticks: number of stolen ticks
- */
-void account_steal_ticks(unsigned long ticks)
-{
- account_steal_time(jiffies_to_cputime(ticks));
-}
-
-/*
* Account multiple ticks of idle time.
* @ticks: number of stolen ticks
*/
--
2.6.6
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