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From: Mauricio Tavares <raubvogel@gmail.com>
Date: Wed, 15 Jan 2020 13:29:43 -0500
Message-ID: <CAHEKYV6tMRCyhWnT9D+LaZ_U7j=wRLcMMU4yjBv1Te72FUYBag@mail.gmail.com>
Subject: Re: CPUs, threads, and speed
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Sender: fio-owner@vger.kernel.org
List-Id: fio@vger.kernel.org
To: Andrey Kuzmin <andrey.v.kuzmin@gmail.com>
Cc: "Gruher, Joseph R" <joseph.r.gruher@intel.com>, "fio@vger.kernel.org" <fio@vger.kernel.org>

On Wed, Jan 15, 2020 at 1:04 PM Andrey Kuzmin <andrey.v.kuzmin@gmail.com> w=
rote:
>
> On Wed, Jan 15, 2020 at 8:29 PM Gruher, Joseph R
> <joseph.r.gruher@intel.com> wrote:
> >
> > > -----Original Message-----
> > > From: fio-owner@vger.kernel.org <fio-owner@vger.kernel.org> On Behalf=
 Of
> > > Mauricio Tavares
> > > Sent: Wednesday, January 15, 2020 7:51 AM
> > > To: fio@vger.kernel.org
> > > Subject: CPUs, threads, and speed
> > >
> > > Let's say I have a config file to preload drive that looks like this =
(stolen from
> > > https://github.com/intel/fiovisualizer/blob/master/Workloads/Precondi=
tion/fill
> > > _4KRandom_NVMe.ini)
> > >
> > > [global]
> > > name=3D4k random write 4 ios in the queue in 32 queues
> > > filename=3D/dev/nvme0n1
> > > ioengine=3Dlibaio
> > > direct=3D1
> > > bs=3D4k
> > > rw=3Drandwrite
> > > iodepth=3D4
> > > numjobs=3D32
> > > buffered=3D0
> > > size=3D100%
> > > loops=3D2
> > > randrepeat=3D0
> > > norandommap
> > > refill_buffers
> > >
> > > [job1]
> > >
> > > That is taking a ton of time, like days to go. Is there anything I ca=
n do to speed it
> > > up?
> >
> > When you say preload, do you just want to write in the full capacity of=
 the drive?
>
> I believe that preload here means what in SSD world is called drive
> preconditioning. It means bringing a fresh drive into steady mode
> where it gives you the true performance in production over months of
> use rather than the unrealistic fresh drive random write IOPS.
>
> > A sequential workload with larger blocks will be faster,
>
> No, you cannot get the job done by sequential writes since it doesn't
> populate FTL translation tables like random writes do.
>
> As to taking a ton, the rule of thumb is to give the SSD 2xcapacity
> worth of random writes. At today speeds, that should take just a
> couple of hours.
>
      When you say 2xcapacity worth of random writes, do you mean just
setting size=3D200%?

> Regards,
> Andrey
>
> > like:
> >
> > [global]
> > ioengine=3Dlibaio
> > thread=3D1
> > direct=3D1
> > bs=3D128k
> > rw=3Dwrite
> > numjobs=3D1
> > iodepth=3D128
> > size=3D100%
> > loops=3D2
> > [job00]
> > filename=3D/dev/nvme0n1
> >
> > Or if you have a use case where you specifically want to write it in wi=
th 4K blocks, you could probably increase your queue depth way beyond 4 and=
 see improvement in performance, and you probably don't want to specify nor=
andommap if you're trying to hit every block on the device.
> >
> > -Joe