[Xen-changelog] [xen stable-4.4] timers: set the deadline more accurately

[patchbot@xxxxxxx]

commit fb5f0c280b252597b052894498c9fac2037cedd7
Author:     Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
AuthorDate: Tue Jun 3 12:12:43 2014 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Jun 3 12:12:43 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 1895a78..f36aebc 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-4.4

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