> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On
> Behalf Of Jens Axboe
> Sent: Tuesday, March 17, 2015 4:56 PM
> To: Urs Schaltegger; [email protected]
> Subject: Re: fio always writes null bytes whatever I do
>
> On 03/12/2015 08:32 AM, Urs Schaltegger wrote:
> > fio always writes null bytes whatever I do. I need random data to avoid
> interference of deduplication solutions (within SSDs or using ZFS).
> >
...
>
> Hmm yes, that looks like a regression. Does the attached work?
>
>
> --
> Jens Axboe
With this change, fio now defaults to spending a lot of
time during writes in:
get_io_u -> small_content_scramble (inlined)
For example, doing writes to a pmem device, perf top shows
the CPU time as:
* 67% pmem memcpy
* 21% fio get_io_u
That disappears if you add
zero_buffers
since the initialization only happens once:
* 89% pmem memcpy
* ...
* 0.02% fio get_io_u
but that means a zero pattern is used, which may be
too easy for some deduplicating storage devices to
handle.
---
Robert Elliott, HP Server Storage
