xen/time: remove blocked time accounting from xen "clockchip"
Laszlo Ersek [Tue, 18 Oct 2011 20:42:59 +0000 (22:42 +0200)]
commit 0b0c002c340e78173789f8afaa508070d838cf3d upstream.

... 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.

Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: John Haxby <john.haxby@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/x86/xen/time.c

index 3d88bfd..13e8935 100644 (file)
@@ -36,9 +36,8 @@ 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)
@@ -115,7 +114,7 @@ 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);
@@ -125,7 +124,6 @@ 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];
 
@@ -141,17 +139,6 @@ 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 */