tex---74@tiscali.it
2011-Sep-23 14:50 UTC
[Xen-users] performance problem with more than one domain U
Hi all. I have a xen server with two virtual machines. When I start the first domain, if I log in to domain and enter the command: time rm -r /mydir I have this time: 0.15 user 0.60 system 3:46.79 elapsed (mydir is 650 MB) But when I create also the second domain, I have this time for the same command: 0.00 user 0.56 system 15:33.38 elapsed that is, 5 times longer! The server has two Opteron six-core cpus and 16 GB RAM The first machine (the one where i did the test) has 8 vcpus and 12 GB RAM The second machine (that II just started) has 1 vcpu and 2 GB RAM The OS on all domains is Ubuntu 10.04, but on domain 0 I have the kernel from debian 2.6.32-5-xen-amd64 and on domain U I have 2.6.32-317-ec2 kernel from ubuntu. The Xen verion is 4.1.1 (compiled from source) I can''t understand why it slows down. Now I am trying to play with xl sched-credit , but it should not be applied because the sum of the ram and of the CPUs of all domains is minor than the total amount of RAM and cores. Thanks in advantage Mario E'' nata indoona: chiama, videochiama e messaggia Gratis da smartphone e da PC: scaricalo da http://www.indoona.com/ _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Todd Deshane
2011-Sep-25 02:37 UTC
Re: [Xen-users] performance problem with more than one domain U
On Fri, Sep 23, 2011 at 10:50 AM, tex---74@tiscali.it <tex---74@tiscali.it> wrote:> The first machine (the one where i did the test) > has 8 vcpus and 12 GB RAM > > The second machine (that II just started) > has 1 vcpu and 2 GB RAMSo the VMs have very different configurations then? Have you tried giving the 2 VMs equal resources? Why wouldn''t you expect a virtual machine with less vCPUs and less memory to perform slower? The rm command might not get the best benchmark to to understand what is going on. Have you considered testing a microbenchmark like iozone? What is your disk backend and is it the same for each? It is a shared directory or are you creating/copying the same directory to each machine for the test? -- Todd Deshane http://www.linkedin.com/in/deshantm http://www.xen.org/products/cloudxen.html http://runningxen.com/ _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
dataworks.biz
2011-Sep-26 14:25 UTC
[Xen-users] Re: performance problem with more than one domain U
----Messaggio originale---- Da: todd.deshane@xen.org Data: 25/09/2011 4.37> So the VMs have very different configurations then? > Have you tried giving the 2 VMs equal resources? > Why wouldn''t you expect a virtual machine with less vCPUs and less memory > to perform slower?OK, maybe I did not explain very well the situation in my previous post. Let''s say I have 2 VM, called VM "A" and VM "B" VM "A" has 8 vcpus and 12 GB RAM VM "B" has 1 vcpu and 2 GB RAM Now, I start the VM A and from the VM A I do the command time rm -r /mydir and I have this time: 0.15 user 0.60 system 3:46.79 elapsed Then I start the VM "B". I just start it, but I am always logged to VM "A". At this point I launch another time the command "time rm -r /mydir" ALWAYS FROM VM "A", not B! And, on the same VM, this time I have: 0.00 user 0.56 system 15:33.38 elapsed The only difference is that now domain "B" is running.>The rm command might not get the best benchmark to to understand what >is going on. Have you considered testing a microbenchmark like iozone?I also did the command: hdparm -tT /dev/mapper/myserver-root Strange thing, this always perform similar when the rm command took 8:42 minutes: Timing cached reads: 5700 MB in 1.99 seconds = 2857.98 MB/sec Timing buffered disk reads: 120 MB in 3.02 seconds = 39.75 MB/sec when the rm command took 1:27 minutes: Timing cached reads: 5466 MB in 1.99 seconds = 2740.00 MB/sec Timing buffered disk reads: 146 MB in 3.01 seconds = 48.48 MB/sec>What is your disk backend and is it the same for each? It is a shared >directory or are you creating/copying the same directory to each >machine for the test?As explained above it is the same VM. I should add that at hardware level (i.e. dom0) I have an Adaptec Raid Card with four 2 GB SATA hard disks in a RAID 10 configuration, if that''s matter Thank You for everything Mario PS: I am sorry, I have some problem with my webmail. So I posted this 3 times ... :-( -- View this message in context: http://xen.1045712.n5.nabble.com/performance-problem-with-more-than-one-domain-U-tp4833868p4841547.html Sent from the Xen - User mailing list archive at Nabble.com. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users