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    SubjectDiscrepancies between Oprofile and vmstat
    We are using an OLTP-type workload on a fully saturated system and have begun seeing a discrepancy between the output of oprofile and vmstat on upstream kernels that was first seen with the 2.6.27 kernel.

    Workload:
    OLTP database workload using QLogic FC cards with MSI-X enabled doing ~50,000 IOPS

    Oprofile (v0.9.3) collection methodology:
    opcontrol --init
    opcontrol --vmlinux=/usr/src/linux-`uname -r`/vmlinux
    opcontrol -e=CPU_CLK_UNHALTED:80000 -e=LLC_MISSES:6000
    opcontrol --start-daemon
    sleep 5
    opcontrol --start
    sleep 60
    opcontrol --stop
    opcontrol --save=$1
    opcontrol --deinit

    Function classification:
    Modules vmlinux and *.ko = kernel, all others = user.

    Results (2.6.30-rc3 kernel):
    vmstat reports ~75% user, 25% kernel
    oprofile reports 70.3808% user, 29.6142% kernel

    Using another profiling tool to confirm, we see 74.784% user, 25.174% kernel.

    Doug Styner
    douglas.w.styner@intel.com


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