On 05/14/2012 01:08 PM, Jeremy Fitzhardinge wrote:
On 05/13/2012 11:45 AM, Raghavendra K T wrote:
On 05/07/2012 08:22 PM, Avi Kivity wrote:
I could not come with pv-flush results (also Nikunj had clarified that
the result was on NOn PLE
I'd like to see those numbers, then.
Ingo, please hold on the kvm-specific patches, meanwhile.
3 guests 8GB RAM, 1 used for kernbench
(kernbench -f -H -M -o 20) other for cpuhog (shell script with while
true do hackbench)
1x: no hogs
2x: 8hogs in one guest
3x: 8hogs each in two guest
kernbench on PLE:
Machine : IBM xSeries with Intel(R) Xeon(R) X7560 2.27GHz CPU with 32
core, with 8 online cpus and 4*64GB RAM.
The average is taken over 4 iterations with 3 run each (4*3=12). and
stdev is calculated over mean reported in each run.
A): 8 vcpu guest
BASE BASE+patch %improvement w.r.t
mean (sd) mean (sd)
patched kernel time
case 1*1x: 61.7075 (1.17872) 60.93 (1.475625) 1.27605
case 1*2x: 107.2125 (1.3821349) 97.506675 (1.3461878) 9.95401
case 1*3x: 144.3515 (1.8203927) 138.9525 (0.58309319) 3.8855
B): 16 vcpu guest
BASE BASE+patch %improvement w.r.t
mean (sd) mean (sd)
patched kernel time
case 2*1x: 70.524 (1.5941395) 69.68866 (1.9392529) 1.19867
case 2*2x: 133.0738 (1.4558653) 124.8568 (1.4544986) 6.58114
case 2*3x: 206.0094 (1.3437359) 181.4712 (2.9134116) 13.5218
B): 32 vcpu guest
BASE BASE+patch %improvementw.r.t
mean (sd) mean (sd)
patched kernel time
case 4*1x: 100.61046 (2.7603485) 85.48734 (2.6035035) 17.6905
What does the "4*1x" notation mean? Do these workloads have overcommit
of the PCPU resources?
When I measured it, even quite small amounts of overcommit lead to large
performance drops with non-pv ticket locks (on the order of 10%
improvements when there were 5 busy VCPUs on a 4 cpu system). I never
tested it on larger machines, but I guess that represents around 25%
overcommit, or 40 busy VCPUs on a 32-PCPU system.
All the above measurements are on PLE machine. It is 32 vcpu single
guest on a 8 pcpu.
(PS:One problem I saw in my kernbench run itself is that
number of threads spawned = 20 instead of 2* number of vcpu. I ll
correct during next measurement.)
"even quite small amounts of overcommit lead to large performance drops
with non-pv ticket locks":
This is very much true on non PLE machine. probably compilation takes
even a day vs just one hour. ( with just 1:3x overcommit I had got 25 x
speedup).
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