Andrey Kuzmin wrote on 03/02/2016 12:26 AM: > 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. I had done it, see my yesterday's e-mail. >> 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. Also done, see the same my e-mail. Thanks, Vlad > 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
