[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] performace issue when turn on apicv
Liuqiming (John) wrote on 2015-06-11: > 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) 1130 > > It 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. Can you retest it based on upstream Xen? Just as you suspected, your backporting may be the culprit. > > > Best regards, Yang _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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