[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] performace issue when turn on apicv
Jan Beulich wrote on 2015-06-18: >>>> On 18.06.15 at 10:02, <john.liuqiming@xxxxxxxxxx> wrote: >> When using FIO to test the performance of SSD passthroughed in vm >> the result show that: When the apicv is on, each >> EXIT_REASON_MSR_WRITE event spent more time than apicv is off. >> >> Following is the xentrace result: >> >> apicv on: >> >> VMExitCode VMExitReason > VMExitCnt VMExitTicks VMExitTicks/VMExitCnt >> >> 0x0000000001 EXIT_REASON_EXTERNAL_INTERRUPT 270334 >> 2730912532 10101.99432 0x0000000012 >> EXIT_REASON_VMCALL 20 438736 21936.8 0x000000001c >> EXIT_REASON_CR_ACCESS 381340 1096174160 >> 2874.532333 0x000000001e EXIT_REASON_IO_INSTRUCTION 413 >> 32958356 79802.31477 0x0000000020 >> EXIT_REASON_MSR_WRITE 111830 818317724 7317.515193 >> 0x000000002d EXIT_REASON_EOI_INDUCED 58944 >> 234914864 3985.390608 0x0000000030 >> EXIT_REASON_EPT_VIOLATION 10 298368 29836.8 >> >> Total 822891 4914014740 >> >> apicv off: >> >> VMExitCode VMExitReason > VMExitCnt VMExitTicks VMExitTicks/VMExitCnt >> >> 0x0000000001 EXIT_REASON_EXTERNAL_INTERRUPT 237100 >> 2419717824 10205.47374 0x0000000007 >> EXIT_REASON_PENDING_VIRT_INTR 792 2324824 2935.383838 >> 0x0000000012 EXIT_REASON_VMCALL 19 >> 415168 21850.94737 0x000000001c >> EXIT_REASON_CR_ACCESS 406848 1075393292 2643.231113 >> 0x000000001e EXIT_REASON_IO_INSTRUCTION 413 >> 39433068 95479.58354 0x000000001f >> EXIT_REASON_MSR_READ 48 150528 3136 0x0000000020 >> EXIT_REASON_MSR_WRITE 229609 1004000084 >> 4372.651264 0x0000000030 EXIT_REASON_EPT_VIOLATION 10 >> 249172 24917.2 >> >> Total > 874839 4541683960 > > And did you drill into _which_ MSR(s) are requiring this much longer > to have their writes handled? After all, that's the relevant thing, > provided the increase of this indeed has anything to do with the > performance issue you're seeing (the absolute increase of 200M ticks > there doesn't mean much for the performance effect without knowing what the > total execution time was). IIRC, APICv doesn't impact the WRMSR's behavior (except EOI, self-IPI and TPR). Cannot understand why APICv will impact it. > > Apart from that I notice that the EXIT_REASON_EOI_INDUCED handling > also adds about the same number of ticks... > > Jan Best regards, Yang _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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