[Xen-changelog] [xen master] credit: change default timeslice to 5ms

[patchbot@xxxxxxx]

commit 348dee3b8afb72cb4713d2e6600b4e86e0cc1723
Author:     George Dunlap <george.dunlap@xxxxxxxxxxxxx>
AuthorDate: Thu Mar 6 12:19:39 2014 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Mar 6 12:19:39 2014 +0100

    credit: change default timeslice to 5ms
    
    The 30ms timeslice was chosen nearly a decade ago now, with cpu
    "burning" workloads in mind.  In the mean time, processors have gotten
    faster and VMEXITs have gotten faster.  A timeslice of 30ms has a
    major cost when running latency-sensitive workloads like network or
    audio streaming: getting caught behind just one or two other VMs can
    introduce a processing delay of up to 60ms, and the "round-robin"
    nature of the credit scheduler means this delay may be introduced
    every time the VM yields for periods of time.
    
    The XenServer performance team at Citrix have done extensive testing
    with various timeslices, including 30ms, 10ms, 5ms, and 2ms.  None of
    the workloads exhibited any performance degradation with a 5ms
    timeslice.
    
    Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
    Reviewed-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
    Acked-by: Tim Deegan <tim@xxxxxxx>
---
 xen/common/sched_credit.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/xen/common/sched_credit.c b/xen/common/sched_credit.c
index db5512e..61553d9 100644
--- a/xen/common/sched_credit.c
+++ b/xen/common/sched_credit.c
@@ -29,9 +29,9 @@
  * Basic constants
  */
 #define CSCHED_DEFAULT_WEIGHT       256
-#define CSCHED_TICKS_PER_TSLICE     3
-/* Default timeslice: 30ms */
-#define CSCHED_DEFAULT_TSLICE_MS    30
+#define CSCHED_TICKS_PER_TSLICE     1
+/* Default timeslice: 5ms */
+#define CSCHED_DEFAULT_TSLICE_MS    5
 #define CSCHED_CREDITS_PER_MSEC     10
 
 
--
generated by git-patchbot for /home/xen/git/xen.git#master

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