[Xen-changelog] [xen stable-4.2] timers: set the deadline more accurately

[patchbot@xxxxxxx]

commit f4185f0c6c7800c86fa07b3115d4e14613efadc3
Author:     Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
AuthorDate: Tue Jun 3 12:23:25 2014 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Jun 3 12:23:25 2014 +0200

    timers: set the deadline more accurately
    
    Program the timer to the deadline of the closest timer if it is further
    than 50us ahead, otherwise set it 50us ahead.  This way a single event
    fires on time rather than 50us late (as it would have previously) while
    still preventing too many timer wakeups in the case of having many
    timers scheduled close together.
    
    (where 50us is the timer_slop)
    
    Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
    master commit: 054b6dfb61eab00d86ddd5d0ac508f5302da0d52
    master date: 2014-05-28 10:07:50 +0200
---
 xen/common/timer.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/xen/common/timer.c b/xen/common/timer.c
index 39de52d..5a7e0f6 100644
--- a/xen/common/timer.c
+++ b/xen/common/timer.c
@@ -492,8 +492,9 @@ static void timer_softirq_action(void)
         deadline = heap[1]->expires;
     if ( (ts->list != NULL) && (ts->list->expires < deadline) )
         deadline = ts->list->expires;
+    now = NOW();
     this_cpu(timer_deadline) =
-        (deadline == STIME_MAX) ? 0 : deadline + timer_slop;
+        (deadline == STIME_MAX) ? 0 : MAX(deadline, now + timer_slop);
 
     if ( !reprogram_timer(this_cpu(timer_deadline)) )
         raise_softirq(TIMER_SOFTIRQ);
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.2

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