On Wed, 2016-06-15 at 23:56 +0000, Bhadauria, Varun wrote:
> Hello Ben
> 
> Thank you for the clarification. I was under the false impression that Linux AIO can be made to
> use SPDK under the hood which is clearly not the case since they will have to go through the
> filesystem. 

I'm sure someone could wrap the AIO interface around the SPDK driver for the specific case where the
user is opening a block device directly with O_DIRECT. It's nearly a 1:1 translation for that case.
Unfortunately, most people use Linux AIO on files instead of block devices.

> BTW are there any known early filesystem implementation besides ceph’s rocksdb based bluestore FS
> which use SPDK.

The only publicly announced one that I'm aware of is Bluestore inside of Ceph. As long as SPDK
continues to be valuable, I fully expect many filesystems with different designs to appear over
time. If you have a particular use case where you'd like some sort of filesystem-like layer on top
of SPDK, I'd love to hear about it. At a minimum, it's useful to collect requirements from a number
of sources.

> 
> Regards,
> Varun Bhadauria
>  
> 
> On 6/15/16, 4:37 PM, "SPDK on behalf of Walker, Benjamin" <spdk-bounces(a)lists.01.org on behalf of 
> benjamin.walker(a)intel.com> wrote:
> 
> > 
> > Can you explain a bit more about why you want to use AIO? Are you referring to Linux AIO or
> > POSIX AIO? If you want to do a performance comparison of Linux AIO and the SPDK NVMe driver then
> > the perf tool is your best bet.
> > 
> > You can run the perf tool against a block device using Linux AIO by binding your NVMe device to
> > the kernel ("./scripts/setup.sh reset" will hand them all back to the kernel) and then doing
> > something like:
> > 
> > ./perf -q 1 -s 4096 -w read -t 10 /dev/nvme0n1 /dev/nvme1n1
> > 
> > -----Original Message-----
> > From: SPDK [mailto:spdk-bounces(a)lists.01.org] On Behalf Of Bhadauria, Varun
> > Sent: Wednesday, June 15, 2016 4:30 PM
> > To: Storage Performance Development Kit <spdk(a)lists.01.org>
> > Subject: [SPDK] SPDK air examples
> > 
> > Hello 
> > 
> > Are there any SPDK examples which use AIO?  Perf.c has very little documentation in the usage
> > for AIO.
> > 
> > Regards,
> > Varun Bhadauria
> > 
> > 
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