[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] performace issue when turn on apicv
Hi, Recently I encounter a strange performance problem with APIC virtualization.My host has Intel(R) Xeon(R) CPU E7-4890 v2 CPU installed which support APIC virtualization and x2apic, and there are 4 socket * 15 cores_per_socket = 60 core available for VM. There is also a SSD disk on host and the host support vt-d, so I can passsthrough this SSD to VM. A VM created with 60 vcpus, 400G memory and SSD device assigned. I pin these vcpus 1:1 to phisical cpu, and in this VM only keep 15 vcpus online.The problem is: when apicv turn on, a significant performace decrease can be observed and it seems related to cpu topology. I had test follow cases apicv=1: 1) ONLINE VCPU {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14} PIN TO PCPU {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14} 2) ONLINE VCPU {0,5,9,13,17,21,25,29,33,37,41,45,49,53,57} PIN TO PCPU {0,5,9,13,17,21,25,29,33,37,41,45,49,53,57} apicv=0: 3) ONLINE VCPU {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14} PIN TO PCPU {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14} 4) ONLINE VCPU {0,5,9,13,17,21,25,29,33,37,41,45,49,53,57} PIN TO PCPU {0,5,9,13,17,21,25,29,33,37,41,45,49,53,57} the result is (the lower the better): 1) 989 2) 2209 3) 978 4) 1130It is a database testcase running on suse11sp3 system in the VM, and I had traced that "read" and "write" syscall get much slower in 2) case. I have disabled NUMA in BIOS, so it seems apicv cause this bad performance when using cpus in different nodes. Can any one shed some light on this?Btw, I am using xen 4.1.5 version with apicv backported, so I am not sure whether something broken when backporting or just apicv behaves this way. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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