Re: [Xen-users] DomU slower with smp?

["Janusz Ulanowski" <janul666@xxxxxxxxx>]

Hi,
Thanks for your answer.
I've done as you said.
Unfortunatelly no difference.
it goes worse when I increase file size or threads number.

for:
time iozone -t 40 -r 2m -s 100m -m -R
DomU with four cpus (each from different core)
 real    6m19.300s
DomU with one cpu
 real 3m32.651s
Dom0
 real    2m37.418s

--
# xm info
host                   : xxxx
release                : 2.6.18.8-xen
version                : #2 SMP Mon May 12 13:19:28 IST 2008
machine                : x86_64
nr_cpus                : 16
nr_nodes               : 1
cores_per_socket       : 4
threads_per_core       : 1
cpu_mhz                : 2393
hw_caps                : bfebfbff:20100800:00000000:00000140:0004e3bd:00000000:00000001
total_memory           : 65530
free_memory            : 12
node_to_cpu            : node0:0-15
xen_major              : 3
xen_minor              : 2
xen_extra              : .1
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 hvm-3.0-x86_32p hvm-3.0-x86_64
xen_scheduler          : credit
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          : Fri May 02 14:23:07 2008 +0100 16888:9733f681d5c5
cc_compiler            : gcc version 4.1.3 20080114 (prerelease) (Debian 4.1.2-19)
cc_compile_by          : root
cc_compile_domain      : lan
cc_compile_date        : Fri May  9 14:41:37 IST 2008
xend_config_format     : 4

Thanks in advance.

2008/5/14 Apparao, Padmashree K <padmashree.k.apparao@xxxxxxxxx>:

The SMP case may be suffering because of context switching.

Can you run the SMP by affintizing the vcpus to specific cores

 

Vcpu on core 1

Vcpu2 on core 2

Vcpu3 on core 3 etc

 

Thanks

-Padma

                                                                              

---

From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Janusz Ulanowski
Sent: Wednesday, May 14, 2008 4:36 AM
To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] DomU slower with smp?

 

Hi,
I just made simple peformance test with iozone tool on xen 3.2.1.

time iozone -t 20 -r 2m -s 100m -m -R

and:

Dom0 - lvm(XFS) : real    1m35.670s


DomU -  2m46.963s
lvm(xfs)
cpus = "4-7"
vcpus=4


DomU - 1m53.772s
lvm(xfs)
cpus = "8"
vcpus=1


It seems DomU  is much slower if using more than one cpu.

am I right?

--
Thanks
Janul

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