On Tue, Mar 1, 2016 at 8:17 AM, Vladislav Bolkhovitin <vst@xxxxxxxx> wrote: > Hello, > > I'm currently looking at one NVRAM device, and during fio tests noticed that each fio > thread consumes 30% of user space CPU. I'm using ioengine=libaio, buffered=0, sync=0 > and direct=1, so user space CPU consumption should be virtually zero. > > That 30% user CPU consumption makes me suspect that this is overhead for internal fio > housekeeping, i.e., scientifically speaking, fio instrumental measurement mistake (I > hope, I'm using correct English terms). > If you believe fio to be 'mistaken', please profile your runs with perf and publish the profile, pointing out what you believe to be a mistake. > Can anybody comment it and suggest how to decrease this user space CPU consumption? > > Here is my full fio job: > > [global] > ioengine=libaio > buffered=0 > sync=0 > direct=1 > randrepeat=1 > softrandommap=1 I suggest you start with switching the random map off as it's known to be expensive and, for some reason, is being maintained even in read-only workloads. Regards, Andrey > rw=randread > bs=4k > filename=./nvram (it's a link to a block device) > exitall=1 > thread=1 > disable_lat=1 > disable_slat=1 > disable_clat=1 > loops=10 > iodepth=16 > > [file1] > > [file2] > > I'm working on million+ IOPS range. > > Thanks, > Vlad > -- > To unsubscribe from this list: send the line "unsubscribe fio" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
