Re: [Xen-devel] Disk iops performance scalability

[John Morrison <john@xxxxxxxxxxxxx>]

Hi,

Yes PARAVIRT_SPINLOCK and its a PV guest.
iops are consistent now as I had a typo in the config file (cpus=)

ioping still showing first 0.1s the rest 0.7/0.8ms

Thanks

John
On 19 Mar 2013, at 12:58, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> wrote:

> On Mon, Mar 18, 2013 at 11:23:00PM +0000, John Morrison wrote:
>> Hi,
>> 
>> Seeing a drop-off in iops when more vcpu's are added:-
>> 
>> 3.8.2 kernel/xen-4.2.1/single domU/LVM backend/8GB RAM domU/2GB RAM dom0
>> 
>> dom0_max_vcpus=2 dom0_vcpus_pin
>> 
>> domU  8 cores  fio result 145k iops
>> domU 10 cores fio result 99k iops
>> domU 12 cores fio result 89k iops 
>> domU 14 cores fio result 81k iops
>> 
>> ioping . -c 3
>> 4096 bytes from . (ext4 /dev/xvda1): request=1 time=0.1 ms
>> 4096 bytes from . (ext4 /dev/xvda1): request=2 time=0.7 ms
>> 4096 bytes from . (ext4 /dev/xvda1): request=3 time=0.8 ms
>> 
>> --- . (ext4 /dev/xvda1) ioping statistics ---
>> 3 requests completed in 2002.0 ms, 1836 iops, 7.2 mb/s
>> min/avg/max/mdev = 0.1/0.5/0.8/0.3 ms
>> 
>> The initial ioping response is good, then a lot of latency with later ones. 
>> Any ideas ?
> 
> Is your guest compiled with PARAVIRT_SPINLOCK and are you using a PV or PVHVM 
> guest?
> 
>> 
>> Thanks
>> 
>> John
>> 
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxx
>> http://lists.xen.org/xen-devel
>> 


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