Commit 0b0c002c authored by Laszlo Ersek's avatar Laszlo Ersek Committed by Konrad Rzeszutek Wilk
Browse files

xen/time: remove blocked time accounting from xen "clockchip" 

... because the "clock_event_device framework" already accounts for idle
time through the "event_handler" function pointer in
xen_timer_interrupt().

The patch is intended as the completion of [1]. It should fix the double
idle times seen in PV guests' /proc/stat [2]. It should be orthogonal to
stolen time accounting (the removed code seems to be isolated).

The approach may be completely misguided.

[1] https://lkml.org/lkml/2011/10/6/10
[2] http://lists.xensource.com/archives/html/xen-devel/2010-08/msg01068.html



John took the time to retest this patch on top of v3.10 and reported:
"idle time is correctly incremented for pv and hvm for the normal
case, nohz=off and nohz=idle." so lets put this patch in.

CC: stable@vger.kernel.org
Signed-off-by: default avatarLaszlo Ersek <lersek@redhat.com>
Signed-off-by: default avatarJohn Haxby <john.haxby@oracle.com>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 283c0972

arch/x86/xen/time.c

+2 −15
Original line number Diff line number Diff line
@@ -37,9 +37,8 @@ static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate); 
/* snapshots of runstate info */

static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate_snapshot);



/* unused ns of stolen and blocked time */

/* unused ns of stolen time */

static DEFINE_PER_CPU(u64, xen_residual_stolen);

static DEFINE_PER_CPU(u64, xen_residual_blocked);



/* return an consistent snapshot of 64-bit time/counter value */

static u64 get64(const u64 *p)
@@ -116,7 +115,7 @@ static void do_stolen_accounting(void) 
{

	struct vcpu_runstate_info state;

	struct vcpu_runstate_info *snap;

	s64 blocked, runnable, offline, stolen;

	s64 runnable, offline, stolen;

	cputime_t ticks;



	get_runstate_snapshot(&state);
@@ -126,7 +125,6 @@ static void do_stolen_accounting(void) 
	snap = &__get_cpu_var(xen_runstate_snapshot);



	/* work out how much time the VCPU has not been runn*ing*  */

	blocked = state.time[RUNSTATE_blocked] - snap->time[RUNSTATE_blocked];

	runnable = state.time[RUNSTATE_runnable] - snap->time[RUNSTATE_runnable];

	offline = state.time[RUNSTATE_offline] - snap->time[RUNSTATE_offline];
@@ -142,17 +140,6 @@ static void do_stolen_accounting(void) 
	ticks = iter_div_u64_rem(stolen, NS_PER_TICK, &stolen);

	__this_cpu_write(xen_residual_stolen, stolen);

	account_steal_ticks(ticks);



	/* Add the appropriate number of ticks of blocked time,

	   including any left-overs from last time. */

	blocked += __this_cpu_read(xen_residual_blocked);



	if (blocked < 0)

		blocked = 0;



	ticks = iter_div_u64_rem(blocked, NS_PER_TICK, &blocked);

	__this_cpu_write(xen_residual_blocked, blocked);

	account_idle_ticks(ticks);

}



/* Get the TSC speed from Xen */

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