Re: blog post on fio write zeroes performance

[Vincent Fu <vincentfu@gmail.com>]

On 11/5/24 15:02, Adam Horshack wrote:
> Nice writeup Vincent. It's been a while since I've looked at the NVMe spec so perhaps I'm asking the wrong question but why is fio managing a data buffer for its handling of the Write Zero command? I would've assumed there's no data payload associated with that NVMe command, thus nothing that should even be subject to internal buffer scrambling inside fio.
> 
> Regards,
> 
> Adam
> 
> 
> ________________________________________
> From: Vincent Fu <vincentfu@gmail.com>
> Sent: Tuesday, November 5, 2024 2:41 PM
> To: fio@vger.kernel.org
> Cc: gost.dev@samsung.com
> Subject: blog post on fio write zeroes performance
> 
> I am pleased to share a blog post about fio write zeroes performance:
> 
> https://github.com/vincentkfu/fio-blog/wiki/How-could-write-zeroes-performance-be-worse-at-higher-queue-depths
> 
> Read about the unexpected performance issue we encountered. Feedback is
> welcome.
> 
> Vincent
> 
> 

When we added write zeroes support for the io_uring_cmd ioengine it was 
not on our mind that the default behavior for fio is to scramble 
buffers. Basically these patches just changed the opcode from a regular 
write to write zeroes.

You do have a good point that perhaps fio should be smart enough to 
avoid touching the buffers when doing write zeroes.

Thanks for the feedback!

Vincent